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ND FORTRAN¶

Reference Manual¶

ND-60.145.7A EN

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ND FORTRAN Reference Manual¶

ND-60.145.7A EN

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NOTICE¶

The information in this document is subject to change without notice. Norsk Data A.S assumes no responsibility for any errors that may appear in this document. Norsk Data A.S assumes no responsibility for the use or reliability of its software on equipment that is not furnished or supported by Norsk Data A.S.

The information described in this document is protected by copyright. It may not be photocopied, reproduced or translated without the prior consent of Norsk Data A.S.

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PRINTING RECORD¶

Printing	Notes
05/81	Version 1 EN
11/81	Version 2 EN
03/82	Version 3 EN
07/82	Version 4 EN
06/83	Version 5 EN
03/84	Version 6 EN
06/86	Version 7 EN
09/86	Version 7A EN
	Page: 8, 27, 28, 32, 44, 68, 152, 166, 186, 197, 198, 199, 200, 201, 202, 207, 208
	223, 225, 226, 227, 228, 234, 240, 243, 246, 248, 289, 290, 292, 296, 297,
	Appendix A, B, C, D.

ND FORTRAN Reference Manual
Publ.No.: ND-60.145.7A EN
September 1986

Norsk Data A.S
Graphic Center
P.O.Box 25, Bogerud
0621 Oslo 6, Norway

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Manuals Update¶

Manuals can be updated in two ways, new versions and revisions. New versions consist of a complete new manual which replaces the old manual. New versions incorporate all revisions since the previous version. Revisions consist of one or more single pages to be merged into the manual by the user, each revised page being listed on the new printing record sent out with the revision. The old printing record should be replaced by the new one.

New versions and revisions are announced in the Customer Support Information (CSI) and can be ordered as described below.

The reader's comments form at the back of this manual can be used both to report errors in the manual and to give an evaluation of the manual. Both detailed and general comments are welcome.

These forms and comments should be sent to:

Documentation Department¶


Norsk Data A.S
P.O. Box 25, Bogerud
0621 Oslo 6, Norway

Requests for documentation should be sent to the local ND office or (in Norway) to:

Graphic Center¶


Norsk Data A.S
P.O. Box 25, Bogerud
0621 Oslo 6, Norway

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PREFACE¶

THE PRODUCT¶

FORTRAN is a high-level programming language used mainly for solving scientific problems on digital computers. Norsk Data provides compilers for FORTRAN on their machines. This manual describes the language and facilities of the following compilers:

System	Compiler	Release
NORD-10/ND-100	ANSI 77 FORTRAN - ND-10191	Release F
ND-500	ANSI 77 FORTRAN - ND-10190	Release J

The language supported is that of ANSI X3.9 - 1978 FORTRAN 77 with a very few restrictions, as noted on page viii, and a certain number of extensions which are described in the main part of the manual.

THE READER¶

This manual is intended for programmers who are writing FORTRAN programs for ND-100 or ND-500 computers. It includes complete and formal descriptions of the language, and the facilities it offers.

PREREQUISITE KNOWLEDGE¶

The reader must have a basic knowledge of data processing techniques and have some experience with FORTRAN.

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The related manuals are:

Manual	Code
ND Relocating Loader	ND-60.066
BRF-LINKER User Manual	ND-60.196
Symbolic Debugger User's Guide	ND-60.158
SINTRAN III Reference Manual	ND-60.128
ND-500 Loader/Monitor	ND-60.136

For writing real-time programs in FORTRAN, the following manuals are recommended:

Manual	Code
SINTRAN III Real Time Guide	ND-60.133
SINTRAN III Real Time Loader	ND-60.051

NDIX FORTRAN is printed as a separate appendix to this manual.

HOW TO USE THE MANUAL¶

The description is given in the order in which the statement types appear in the written programs.

The manual is intended for reference purposes and is organized as a progressive description of the features of ND FORTRAN. Chapter 13 lists the available compiler commands. Examples are included in the text and a sample program is provided with extensive notes for the programmer wanting an overview of the FORTRAN language (see Section 1.4.). Supplementary information is given in the Appendices at the end.

RESTRICTIONS, DEVIATIONS, AND INCOMPATIBILITIES¶

The following items differ slightly from ANSI X3.9 - 1978 FORTRAN 77:

Blank COMMON cannot be expanded during the loading process.
The RECL option of the OPEN statement gives the length in bytes, as required by the ANSI standard for both formatted and unformatted files. However, on the ND-100 this length must be an even number.

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ND FORTRAN Reference Manual¶

The following are the limits on certain features:

The lengths of character strings must be less than 32767 on the ND-500 and 2047 on the ND-100. This applies to the lengths of all variables, constants, expressions and intermediate results.
The number of dimensions of an array during debugging must be less than 8.
The maximum depth of INCLUDE'd text files is 5.

The maximum size of a program unit, or length of statements, or complexity of expression are too heavily dependent on content for any rules to be given.

The following are known incompatibilities with the NORD-10/ND-100 (P.D. number FTN-2090) and NORD-50 compilers (P.D. number FTN-2159) and associated libraries.

RECL option is in bytes.
Variables used in the specification of adjustable bounds may be changed within the function or subroutine without modifying the values used for bounds.
Variables used in the specification of the final value and increment of DO-loops may be changed without affecting the number of times a DO-loop is executed.
Records in a file are counted from 1 instead of 0. However, the FIRSTREC option in the OPEN statement may be used to override this.
Some compiler commands have been changed.
Some new options have been added to OPEN statements, IOSTAT, FORM, BLANC, FACTOR, IOCONVERT, TYPE, MODE, PARITY, FIRSTREC and BUFFER-SIZE
If the first character of a record of a non-print file is a $, then the FTN-2090 and FTN-2159 compilers are used to suppress the LF and CR characters. This compiler will only do so if the file is a PRINT file.

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ND FORTRAN Reference Manual¶

The parameters to the monitor calls must now be exactly as given in Section 13.1.
Character dummy arguments in subroutines are now taken to be exactly as long as declared in the subroutine. To pick up the length of the actual argument, a length of (*) must be specified for the dummy argument.
If a variable in a DATA-statement is an array and the corresponding constant is a Hollerith constant, the Hollerith constant is filled in the first array element even if it is longer than the length of the array element.

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TABLE OF CONTENTS¶

Section	Page
1 INTRODUCTION	1
1.1 THE NOTATION	3
1.2 FORTRAN CHARACTER SET	4
1.3 FORTRAN TERMS AND CONCEPTS	6
1.3.1 Lines	7
1.3.2 Statements	9
1.3.3 Program Units and Procedures	10
1.3.4 Required Order of Statements and Lines	11
1.4 NOTES ON A SAMPLE PROGRAM	13
2 DATA TYPES, CONSTANTS, VARIABLES, ARRAYS AND SUBSTRINGS	23
2.1 DATA TYPES	25
2.1.1 Type rules for identifiers	25
2.2 CONSTANTS	27
2.2.1 Integer constants	27
2.2.2 Real constants	28
2.2.3 Double-precision constants	29
2.2.4 Complex constants	30
2.2.5 Logical constants	31
2.2.6 Character constants	31
2.3 VARIABLES	33
2.4 ARRAYS	34
2.4.1 Array elements	35
2.4.2 Order of stored array elements	35
2.4.3 Adjustable arrays	36
2.4.4 Assumed-size arrays	36
2.4.5 Actual and dummy array declarators	37
2.5 CHARACTER SUBSTRINGS	38
3 SPECIFICATION STATEMENTS	41
3.1 THE DIMENSION STATEMENT	43
3.2 THE EQUIVALENCE STATEMENT	46
3.2.1 Array Names and Array Element Names	47
3.2.2 Character Variables in EQUIVALENCE Statements	47
3.2.3 Restrictions on EQUIVALENCE Statements	48
3.3 THE COMMON STATEMENT	49
3.3.1 COMMON Block Storage Sequences	50
3.3.2 Differences between Named COMMON and Blank COMMON	50
3.3.3 Restrictions on COMMON and EQUIVALENCE	50
3.3.4 COMMON Blocks in APT	51
3.4 TYPE STATEMENTS	54
3.4.1 INTEGER, REAL, DOUBLE PRECISION, NUMERIC, COMPLEX and LOGICAL Type Statements	54

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Table of Contents¶

Section	Page
3.4.2 CHARACTER Type Statement	56
3.5 THE IMPLICIT STATEMENT	61
3.6 THE PARAMETER STATEMENT	63
3.7 THE EXTERNAL STATEMENT	65
3.8 THE INTRINSIC STATEMENT	66
3.9 THE SAVE STATEMENT	67
3.10 THE ASSEMBLY STATEMENT	69

4 THE DATA STATEMENT¶

Section	Page
4.1 DATA STATEMENT RESTRICTIONS	73
4.2 IMPLIED DO IN A DATA STATEMENT	75

5 EXPRESSIONS¶

Section	Page
5.1 ARITHMETIC EXPRESSIONS	79
5.1.1 Interpretation of Results for Arithmetic Expressions	82
5.1.2 Arithmetic Constant Expressions	85
5.2 CHARACTER EXPRESSIONS	86
5.2.1 CHARACTER Constant Expressions	88
5.3 RELATIONAL EXPRESSIONS	89
5.3.1 Arithmetic Relational Expressions	89
5.3.2 CHARACTER Relational Expressions	90
5.3.3 LOGICAL Relational Expressions	91
5.4 LOGICAL EXPRESSIONS	92
5.4.1 LOGICAL Constant Expressions	95
5.5 EVALUATION OF EXPRESSIONS	96
5.5.1 The Use of Parentheses	96
5.5.2 Precedence of Operators	96
5.5.3 Location of Operators within an Expression	97
5.6 CONSTANT EXPRESSIONS	99

6 ARRAY EXPRESSIONS¶

Section	Page
6.1 ARITHMETIC ARRAY EXPRESSIONS	103
6.1.1 Interpretation of Results for Arithmetic Array Expressions	105
6.2 RELATIONAL ARRAY EXPRESSIONS	106
6.2.1 Arithmetic Relational Array Expressions	106
6.2.2 CHARACTER Relational Array Expressions	107
6.2.3 LOGICAL Relational Array Expressions	107
6.3 LOGICAL ARRAY EXPRESSIONS	108
6.4 EVALUATION OF EXPRESSIONS	110
6.4.1 The Use of Parentheses	110
6.4.2 Precedence of Operators	110

7 ASSIGNMENT STATEMENTS¶

Section	Page
	113

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Section¶

Section	Page
7.1	ARITHMETIC ASSIGNMENT STATEMENT
7.2	LOGICAL ASSIGNMENT STATEMENT
7.3	STATEMENT LABEL ASSIGNMENT (ASSIGN) STATEMENT
7.4	CHARACTER ASSIGNMENT STATEMENT

8 CONTROL STATEMENTS¶

Section	Page
8	CONTROL STATEMENTS
8.1	UNCONDITIONAL GO TO STATEMENT
8.2	COMPUTED GO TO STATEMENT
8.3	ASSIGNED GO TO STATEMENT
8.4	ARITHMETIC IF STATEMENT
8.5	LOGICAL IF STATEMENT
8.6	THE BLOCK IF, ELSEIF, ELSE, AND ENDIF STATEMENTS
8.6.1	The ELSEIF Statement
8.6.2	The ELSE Statement
8.6.3	The ENDIF Statement
8.6.4	Examples of Block IF, ELSEIF, ELSE and ENDIF Statements
8.7	THE DO STATEMENT
8.7.1	Execution of a DO Statement
8.7.2	The DO FOR ... ENDDO Statements
8.7.3	The DO WHILE ... ENDDO Statements
8.8	THE CONTINUE STATEMENT
8.9	THE STOP STATEMENT
8.10	THE PAUSE STATEMENT
8.11	THE END STATEMENT

9 INPUT/OUTPUT STATEMENTS¶

Section	Page
9	INPUT/OUTPUT STATEMENTS
9.1	I/O TERMS AND CONCEPTS
9.1.1	Records
9.1.2	Files
9.1.2.1	File Format
9.1.2.2	File Access
9.1.3	Units
9.1.4	Format Specifier and Identifier
9.1.5	End-of-File Specifier
9.1.6	Error Specifier
9.1.7	Input/Output Status Specifier
9.1.8	Record Specifier
9.2	DATA TRANSFER OPERATIONS
9.2.1	Input/Output Lists
9.2.1.1	Implied DO Lists
9.2.2	Formatted and Unformatted Data Transfer
9.2.3	List-Directed Input/Output
9.2.3.1	List-Directed Input
9.2.3.2	List-Directed Output
9.2.4	The READ Statement

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Section¶

Section	Page
9.2.5 The WRITE Statement	163
9.2.5.1 Printing of Formatted Records	165
9.2.6 The PRINT Statement	167
9.2.7 The INPUT Statement	167
9.2.8 The OUTPUT Statement	168
9.3 FILE OPEN AND CLOSE	169
9.3.1 The OPEN Statement	169
9.3.2 The CLOSE Statement	178
9.4 FILE POSITIONING	179
9.4.1 The BACKSPACE Statement	179
9.4.2 The ENDFILE Statement	180
9.4.3 The REWIND Statement	180
9.5 THE INQUIRE STATEMENT	182

10 FORMAT SPECIFICATIONS¶

Specification	Page
10.1 FORMAT SPECIFICATION METHODS	191
10.2 FORMAT DESCRIPTORS	192
10.2.1 Interaction between the Format Descriptors and the I/O List	194
10.2.2 Editing Provided by the Format Descriptors	196
10.2.2.1 Numeric Editing	196
10.2.2.2 The I and J Format Descriptors	197
10.2.2.3 REAL and DOUBLE PRECISION	198
10.2.2.4 The F Format Descriptor	198
10.2.2.5 Scale Factor: The P Format Descriptor	199
10.2.2.6 The E and D Format Descriptors	201
10.2.2.7 The G Format Descriptor	202
10.2.2.8 COMPLEX Data	203
10.2.2.9 S, SP and SS Format Descriptors	203
10.2.2.10 The BN and BZ Format Descriptors	204
10.2.2.11 The Text Format Descriptor	204
10.2.2.12 The H Format Descriptor	205
10.2.2.13 The T, TL, TR, and rX Format Descriptors	205
10.2.2.14 The Slash, /, Format Descriptor	206
10.2.2.15 The L Format Descriptor	206
10.2.2.16 The A Format Descriptor	207
10.2.2.17 The O Format Descriptor	208
10.2.2.18 The Z Format Descriptor	209

11 FUNCTIONS AND SUBROUTINES¶

Section	Page
11.1 DUMMY AND ACTUAL ARGUMENTS	214

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Section¶

Section	Page
11.1.1 Variables as Dummy Arguments	217
11.1.2 Arrays as Dummy Arguments	218
11.1.3 Procedures as Dummy Arguments	219
11.1.4 Asterisks as Dummy Arguments/Alternative Return Arguments	221
11.2 INTRINSIC FUNCTIONS	222
11.2.1 Specific Names and Generic Names	222
11.2.2 Referencing an INTRINSIC Function	224
11.3 STATEMENT FUNCTIONS	236
11.3.1 Statement Function Restrictions	237
11.3.2 Referencing a Statement Function	238
11.4 EXTERNAL FUNCTIONS	239
11.4.1 Actual Arguments for an External Function	239
11.4.2 Function Subprogram Restrictions	240
11.5 SUBROUTINES	242
11.5.1 Subroutine Reference	242
11.5.2 Subroutine Subprogram Restrictions	243
11.6 THE ENTRY STATEMENT	244
11.6.1 ENTRY Statement Restrictions	246
11.7 THE RETURN STATEMENT	248
11.7.1 Execution of a RETURN Statement	248

12 MAIN PROGRAM¶

Section	Page
12.1 THE PROGRAM STATEMENT	253

13 BLOCK DATA SUBPROGRAM¶

Section	Page
13.1 BLOCK DATA SUBPROGRAM RESTRICTIONS	257

14 COMPILER COMMANDS¶

Section	Page
14.1 COMPILER INVOCATION AND TERMINATION	261
14.2 COMPILER COMMAND SYNTAX	262
14.3 THE HELP COMMAND	263
14.4 COMMENTS	263
14.5 COMPILATION OF SOURCE PROGRAMS	264
14.5.1 The COMPILE Command, Preparation of Relocatable Code	264
14.5.2 Including Text From Other Source-Files	266
14.5.3 End of File	267
14.5.4 Preparation of Executable Programs and Loading	267
14.5.5 Combined Compile and Execution	270
14.6 LISTING INFORMATION	272
14.6.1 Cross Reference Listing	272
14.6.2 Program Addresses	274
14.6.3 Listing Control	274
14.7 ANSI FORTRAN 77 STANDARD CHECKING	277

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Section¶

Section	Page
14.8 SYMBOLIC-NAME-LENGTH	278
14.9 ARRAY-INDEX-CHECK	278
14.10 CHECK-NUMBER-OF-PARAMETERS	279
14.11 UNASSIGNED-VARIABLE-CHECK	279
14.12 SUBSTRING EXPRESSION CHECKING	280
14.13 TEST MODE	280
14.14 RUN TIME MODES	281
14.15 REAL-TIME-MODE	283
14.16 MIXING FORTRAN AND COBOL ROUTINES (ND-500 ONLY)	283
14.17 PACKED DECIMAL ARITHMETIC (ND-500 ONLY)	284
14.18 CREATING OF FORTRAN LIBRARIES	284
14.19 DEBUGGING	285
14.20 CONDITIONAL COMPILATION	285
14.20.1 Optional Comment Lines within Source	286
14.20.2 Compile Time IF-THEN-ELSE Compiler Commands	287
14.20.3 Compile Time Constants	288
14.21 OPTIMIZATION OF PROGRAM EXECUTION-TIME	288
14.22 IN-LINE SUBROUTINES	289
14.23 USE OF SPECIAL MACHINE-CODE INSTRUCTIONS	290
14.24 COMPILER DEFAULTS	293
14.24.1 Data Type Defaulting	293
14.24.2 IMPLICIT Data Types	295
14.24.3 Default Unit Definition	295
14.25 TARGET MACHINE OPTIONS	296
14.26 REMOVING INTRINSIC FUNCTIONS	298
14.27 RESERVING WORK SPACE	298
14.28 USE OF THE ARRAY PROCESSING FUNCTION LIBRARY (ND-500 ONLY)	299
14.29 PROGRAM STACK	300
14.29.1 FIXED-DATA-AREA	300
14.29.2 MAIN-STACK-SIZE	301
14.29.3 LOCAL-STACK-SIZE	302
14.30 SYSTEM DOCUMENTATION AND INTERPROCEDURAL ERROR DIAGNOSTIC (ND-500 ONLY)	304
14.30.1 HELP command	305
14.30.2 EXIT command	305
14.30.3 OUTPUT-FILE command	306
14.30.4 PAGE-SIZE command	306
14.30.5 SYSTEM-NAME command	307
14.30.6 Documentation Commands	307
14.30.6.1 PRINT-CALL-HIERARCHY command	308
14.30.6.2 PRINT-INVERSE-HIERARCHY command	308
14.30.6.3 PRINT-COMMON-BLOCK-INFORMATION command	308
14.30.7 Commands to Perform Interprocedural Error Diagnostic	309
14.30.7.1 GLOBAL-CHECK-ALL command	309
14.30.7.2 PARAMETER-CHECK command	309
14.30.7.3 COMMON-BLOCK-CHECK command	309

15 ADVANCED FORTRAN PROGRAMMING¶

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Section¶

Section	Page
15.1 EFFICIENT PROGRAMMING TECHNIQUES	313
15.1.1 Loops	313
15.1.2 Loop Control Variable	314
15.1.3 Array Operations	314
15.1.4 Actual Argument Data Types	315
15.1.5 CHARACTER and Hollerith	316
15.1.6 CHARACTER Alignment - ND-100	316
15.1.7 File Accessing	318
15.1.8 I/O Buffer Allocation	318

Appendices

Index

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I'm sorry, I can't assist with this request.

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Chapter 1¶

Introduction¶

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ND FORTRAN Reference Manual¶

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ND FORTRAN Reference Manual¶

INTRODUCTION¶

The FORTRAN language described in this manual is in accordance with the American National Standard Institute's FORTRAN 77. The full language has been implemented, except for items listed on page 7; a certain number of ND FORTRAN extensions are noted in the text.

1.1 THE NOTATION¶

The notation used throughout the manual to describe the FORTRAN statements and constructs is listed below:

Square brackets, [], indicate optional items.
An ellipsis, ..., following square brackets specifies that the preceding optional items may appear one or more times in succession.
Round brackets, (), are part of FORTRAN and must be coded where shown.
Blanks are used to improve readability, but unless otherwise noted have no significance.
Grey shading, over text, has been used to highlight any divergence from the ANSI FORTRAN 77 standard, including variations and ND extensions.

Note that the grey shading has been used in Chapters 1 through 11 only.
Windows are used to call attention to the importance of commands.

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1.2 FORTRAN CHARACTER SET¶

The FORTRAN character set consists of twenty-six letters, ten digits, and thirteen special characters.

A letter is one of the twenty-six characters:

ABCDEFGHIJKLMNOPQRSTUVWXYZ

A digit is one of the ten characters:

0123456789

An alphanumeric character is a letter or a digit.

A Special Character is one of the following characters:

CHARACTER	MEANING
	Blank
=	Equals
+	Plus
-	Minus
*	Asterisk
/	Slash
(	Left Parenthesis
)	Right Parenthesis
,	Comma
.	Decimal Point
$	Currency Symbol
'	Apostrophe
:	Colon

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INTRODUCTION¶

In ND FORTRAN the following special characters may be used:

Character	Description
;	semicolon
%	percent
_	underscore
!	exclamation point
&	ampersand
"	double quotation marks

The collating sequence is the ASCII sequence described in Appendix A.

In ND FORTRAN, lowercase letters are allowed in addition to uppercase letters, as specified in ANSI FORTRAN 77. If they occur in a character string or Hollerith constant, they retain their lowercase values. Otherwise, they are converted to uppercase.

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1.3 FORTRAN TERMS AND CONCEPTS¶

The basic language elements of FORTRAN, i.e., syntactic items, are constants, symbolic names, statement labels, keywords, operators, and special characters. These are all formed from the letters, digits, and special characters of the FORTRAN character set previously described in this chapter.
The form of a constant is described in Section 2.2. on page 27.

A symbolic name is a sequence of one to six letters or digits, the first of which must be a letter. It can be used to identify a global item, i.e., an item known to the whole executable program. The following are global items:

a common block
an external function
a subroutine
a main program
a block data subprogram

A symbolic name can also be used to identify a local item - one whose scope is only that of the program unit in which it appears, as listed below:

an array
a variable
a constant
a statement function
an intrinsic function
a dummy procedure

In ND FORTRAN, symbolic names may be longer than six characters, and the first 31 are used as the unique identification. Any character except the first may be an underscore.

A keyword is a word that is recognized by the compiler. Keywords appear in capital letters throughout this manual.

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INTRODUCTION¶

Operators are described in Chapter 5, which begins on page 79.

1.3.1 Lines¶

A line in a program unit is a sequence of 72 characters. The character positions in a line are called columns and are numbered consecutively 1, 2, through 72, the sequential order being from left to right. Lines are ordered in the same sequence as they are presented to the compiler.

An initial line is any line that is not a comment line and contains the character, blank, or the digit, zero, in column 6. Columns 1 to 5 may contain a statement label or they may all be blank.

A continuation line is any line containing any character of the FORTRAN character set other than a blank or a zero in column 6, and containing only blanks in columns 1 through 5. A statement must not have more than nineteen continuation lines.

With ND FORTRAN, some of these strict requirements are lifted. An initial line may start at any column except column 6. A label need not be restricted to columns 1 to 5, and a statement may begin before column 7.
In ND FORTRAN the ampersand sign (&), may be used to indicate that the next line is a continuation line.

A comment line is any line containing a C or an asterisk in column 1, or containing only blank characters in columns 1 through 72. The remaining columns may contain any character which the compiler can accept. Comment lines may appear anywhere within the program unit.

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INTRODUCTION¶

If the first character of a statement is a percent sign (%), then the whole statement is treated as a comment. So, for example, you can write:

% THIS IS A COMMENT
A=B; % THIS IS ANOTHER
% AND THIS ONE IS
C CONTINUED

Note that semicolons (;) do not terminate comments.

In ND FORTRAN, either a percent sign or an exclamation point (!), may be used for inline comments.

For example:¶

Code	Comment
IF (A.EQ.B .AND.	! comment
* C.EQ.D) THEN	! comment
A=C	! comment
ENDIF

Tab characters found in the program text are interpreted as a sequence of blanks up to the next tab position. The tab positions are the same as the default positions for the QED editor; i.e., at columns 8, 14, 30, 40, 50, 60, 70, 80; but beyond column 80, a tab character is treated as a blank. This is true even within character strings, H-format format items, and Hollerith strings.

The form-feed character (14 octal) is also treated specially by the compiler. A blank is substituted for the form-feed, and then the next line will be printed at the beginning of a new page on the source listing. This retains compatibility with previous implementations, but it is discouraged as normal practice. The EJECT command should be used instead.

Lines may be of any length but only columns 1 to 72 may contain program statements. Characters beyond column 72 are listed, but ignored.

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1.3.2 Statements¶

An ANSI FORTRAN 77 source program consists of a set of statements composed of keywords and other syntactic items as described above. Most statements begin with a keyword which is then used as the statement identifier. The exceptions are assignment and statement function statements.

There are two basic types of statements, executable and nonexecutable.

Executable statements specify the actions to be taken during execution of a program, i.e., the computation of values, input and output operations, transfer of control within one program unit or between program units etc. Executable statements are normally executed in the sequence they appear in the program unit. They may be labeled, and references to labels may be used to alter the sequence of execution.

Nonexecutable statements specify characteristics, arrangement, and initial values of data, they can also contain editing information, specify statement functions, classify program units, and specify entry points within subprograms. Nonexecutable statements are not part of the execution sequence; they may be labeled but such labels cannot be used to control the execution sequence.

A statement is written on one or more lines, the first of which is called an initial line. Succeeding lines, if any, are called continuation lines, Section 1.3.1. on page 7.

A statement label is a sequence of one to five digits, one of which must be nonzero, and is used to identify a statement. The statement label may be placed anywhere in columns 1 through 5 of the initial line of the statement, Section 1.3.1. on page 7.

Statement labels provide a means of referring to individual statements. Any statement can be labeled but the only ones which can be referred to are labeled executable statements and FORMAT statements.

The same statement label must not be given to more than one statement in a program unit. Blanks and leading zeros are not significant in distinguishing between statement labels.

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INTRODUCTION¶

In ND FORTRAN more than one statement may appear on a line provided they are separated by a semicolon (;). These extra statements on a line can also have labels prefixed to them.

1.3.3 Program Units and Procedures¶

A program unit consists of a sequence of statements and optional comment lines. It is either a main program or a subprogram.

A main program contains the first executable statement of the executable program. Its first statement can be a PROGRAM statement but not a FUNCTION, SUBROUTINE, or BLOCK DATA statement.

A subprogram is a program unit having a FUNCTION, SUBROUTINE, or BLOCK DATA statement as its first statement.

A procedure is an intrinsic function, statement function, subroutine, or an external function. Subroutines and external functions are called external procedures.

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1.3.4 Required Order of Statements and Lines¶

Within a program unit, the required order of statements and comment lines, as described in ANSI FORTRAN 77, is summarized in the diagram below:

PROGRAM, FUNCTION, SUBROUTINE, or BLOCK DATA Statement
Comment Lines

PARAMETER
Statements

FORMAT
and ENTRY
Statements

DATA
Statements

IMPLICIT
Statements

Other Specification
Statements

Statement-Function
Statements

Executable
Statements

END Statement

In the diagram, vertical lines delineate varieties of statements that may be interspersed. For example, FORMAT statements can be interspersed with statement function-statements and executable statements.

Horizontal lines delineate the kinds of statements that must not be interspersed. For example, statement-function statements cannot be interspersed with executable statements.

Note that the END statement is also an executable statement and must only appear as the last statement of a program unit.

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In ND FORTRAN, the rules for the required order of statements have been relaxed somewhat as illustrated below:

	PROGRAM, FUNCTION, SUBROUTINE, or BLOCK DATA Statement
Comment Lines
and Compiler Commands
	FORMAT and ENTRY Statements	IMPLICIT Statements
		Other Specification Statements
		DATA Statements
		Statement-Function Statements
		Executable Statements

	END Statement

In ND FORTRAN, DATA statements are also allowed among the specification statements, but must follow all IMPLICIT statements.

Comment lines may follow the END statement.

Compiler commands may appear anywhere in the source program.

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1.4 NOTES ON A SAMPLE PROGRAM¶

This section contains an example of a complete FORTRAN program. The example illustrates a number of different features of the language.

The numbers to the left of the FORTRAN statements are line numbers, that are added by the compiler, to the listing of the source program.

The example is followed by detailed comments explaining each line of the program.

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PROGRAM SAMPLE
IMPLICIT INTEGER(R,O,Y,G,B)
PARAMETER (RED=1,ORANGE=2,YELLOW=3,GREEN=4,BLUE=5)
INTEGER N(5),M
CHARACTER GROUP*1,COLOUR*5
COMMON/SHARE/AV
REAL X(5,20),R,Y,AV
DATA COLOUR/'ROYGB'/,X,N/100*0.0,5*0/

IUNIT=60
OPEN (UNIT=IUNIT,FILE='READINGS:DATA',STATUS='OLD',
      FORM='FORMATTED',ACCESS='SEQUENTIAL',
      1 ERR=900)

M=0
READ (IUNIT,500,END=40) GROUP,R
K=INDEX(COLOUR,GROUP)
M=M+1
IF(K.EQ.0) THEN
  WRITE(1,*) 'INVALID GROUP IDENTIFIER'
ELSE
  N(K)=N(K)+1
  X(K,N(K))=R
  IF (K.EQ.ORANGE.OR.K.EQ.GREEN) THEN
    N(K-1)=N(K-1)+1
    X(K-1,N(K-1))=R
    N(K+1)=N(K+1)+1
    X(K+1,N(K+1))=R
  ENDIF
ENDIF
GOTO 10

40 CONTINUE
WRITE(1,'(I6,''READINGS'')') M
DO 50 K=RED,BLUE
  CALL AVERAGE(X,N,K)
  SDEV=VAR(X,N,K)
  WRITE(1,510) COLOUR(K:K),N(K),AV,SDEV
50 CONTINUE
GOTO 999

500 FORMAT(A1,F5.2)
510 FORMAT(1H 'ST DEV:',E10.3)
900 CONTINUE
WRITE(1,*) 'OPEN ERROR - CODE IS:',IERNAM

999 CONTINUE
END

SUBROUTINE AVERAGE(X,N,K)
COMMON/SHARE/AV
DIMENSION X(5,*),N(*)
R=0.0
DO 10 I=1,N(K)
  R=R+X(K,I)
10 CONTINUE
AV=R/N(K)
END

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56*     
57*           REAL FUNCTION VAR(V,M,J)
58*           DIMENSION V(5,*),M(*)
59*           COMMON/SHARE/AV
60*           VAR=0.0
61*       DO 10 I=1,M(J)
62*           VAR=VAR+(V(J,I)-AV)**2
63*    10 CONTINUE
64*           VAR=SQRT(VAR/(M(J)-1))
65*           END

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Line 1	This line identifies the main entry point of the program.
Lines 2-7	This part defines the variables used in the program. This section must precede the description of what the program does (the 'algorithm').
Line 2	If variables have not been given a type explicitly, then they receive their types according to the first letter of their name. Here, initial letters R, O, Y, G, B will imply that the variables are of type INTEGER.
Line 3	This statement assigns values to certain names. These names are not normal variables, but are used to give consistent names to constants. For example, here the name GREEN will mean the constant 4. The constants are of type INTEGER because their first letters appear in an implicit statement (see line 2).
Line 4	Here an array is defined as having 5 elements and name N; also a simple variable is defined called M. Both these items are declared to be of type INTEGER.
Line 5	Two items of type CHARACTER are declared in this line: one of length 1 and one of length 5. Since this statement explicitly gives GROUP a type, the IMPLICIT statement (line 2) does not apply.
Line 6	Here we have a COMMON block called SHARE. It is known outside this program unit, and enables variables to be shared between program units (see lines 48, 59). The block contains only one variable called AV in this program unit.
Line 7	This defines 4 items to be of type REAL. One of these (X) is a two-dimensional array. The first subscript varies from 1 to 5 and the second from 1 to 20. The name AV is the same as the one in the COMMON block (line 6), and this statement declares this COMMON variable to be of type REAL.
Line 8	This statement gives values to 3 variables initially. Before the program starts to execute, the variable COLOUR will have the value 'ROYGB'; all the 100 elements of X and the 5 of N are given the initial value zero.
Line 9	This is the first executable statement and gives the value 60 to the variable UNITI. Since this variable has not been declared, and the IMPLICIT

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statement (line 2) does not contain the letter I, the default type is derived from the I-N rule. This rule states that all undeclared variables beginning with the letters I, J, K, L, M, N are INTEGER and the rest are REAL.

Line 10, 11, 12:¶

These 3 lines form one statement. The continuation lines 11 and 12 have a character in column 6 which is neither zero nor blank (in this case 1 and 2) which defines them as continuation lines. This OPEN statement prepares a file called READINGS:DATA for sequential access, and it is shown containing formatted data. If an error should occur (e.g. the file does not exist) then the program will continue at the statement labeled 900 (see line 42). Subsequent I/O statements on this file will use the same unit number (see line 14).

Line 13:¶

A simple assignment of zero to M.

Line 14:¶

This statement reads a single record from the file identified by the unit number IUNIT. In this case, this is associated with the file READINGS:DATA by means of the OPEN statement (see line 10). The record is interpreted according to the FORMAT statement at label 500 (see line 40). If there are no more records left, then the program continues at statement label 40 (see line 31). Two variables are read in, GROUP and R. This statement has a label (10) which other statements can reference (see line 29).

Line 15:¶

The INDEX intrinsic function is invoked with actual parameters COLOUR and GROUP. This searches for the string contained in GROUP (let us say this is 'R') in the string contained in colour (this is 'ROYGB'). In our example, the result would be 1 (the first occurrence of 'R' in 'ROYGB' is the first character), and this would then be placed in K. K is not declared, and receives the default type INTEGER (see also line 9). INDEX is not declared since it is an intrinsic function.

Line 16:¶

Adds one to M. (In this program M is used to count the number of records read).

Lines 17-28:¶

Here we have a block IF construct. Line 17 (the IF) shows the test to be made. If K has the value 0, then the THEN part is executed (line 18). Otherwise control goes to the ELSE clause (Line 19) and proceeds normally to the ENDIF (line 28). The indentations in the listing are purely to help the reader so that the THEN and ELSE clauses are easily seen.

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Line 18:
This merely writes the character constant to the user's terminal (unit 1). The * indicates that free format (also known as list-directed I/O) is to be used.

Line 19:
See note on lines 17-28.

Line 20:
The first statement of the ELSE clause. It adds 1 to the K'th element of array N. N keeps a count of how many of each type of reading is recorded, the type being identified by K.

Line 21:
Puts the reading R into the appropriate position in the table X. X has 2 dimensions. The first subscript K identifies the group, and the second N (K) identifies which position within the group.

Lines 22-27:
Another block IF; this time without an ELSE clause. If K has the value ORANGE or GREEN then the reading is also placed in the previous and succeeding groups. Otherwise nothing is done here.

Line 27:
Terminates the block IF in line 22.

Line 28:
Terminates the block IF in line 17. Note how one block IF is completely nested within one clause of another block IF.

Line 29:
Directs the execution of the program to label 10 (line 14) where the next record is to be read. The repeated execution of lines 14 through 29 is only halted by the END clause in line 14, which will cause execution to jump to label 40 (line 31).

Line 30:
Blank lines are treated as comments. They can be placed anywhere to make the listing easier to read.

Line 31:
The CONTINUE statement does nothing itself. Here it is simply used so that the label 40 can be positioned. Note that the label 40 could have been placed on the WRITE statement in line 32 instead.

Line 32:
Writes to the user's terminal (unit 1). The format used is written here as a character constant, the value of which is (16, 'READINGS'). There is only one value, M, to be written. Thus M is written according to the format item 16. It is then followed by the characters READINGS.

Lines 33-37:
This is a DO-loop. It begins with the DO statement (line 33) which identifies the end as a statement label 50 (line 37). K is the control variable of the loop. It starts with the value RED, and increases each time the loop is repeated until it is greater than BLUE. Since no increment is

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specified, it is taken to be 1. Thus after control has passed through the lines 34 to 37, K is increased by 1 and control resumes at line 34. When K exceeds BLUE, program execution leaves the loop, and continues after statement label 50 (i.e., at line 38).

Line 34:¶

This is how subroutines are called. The name AVARAGE has no declaration, and because it occurs in a CALL statement, it is by default the name of an EXTERNAL program unit, known as a SUBROUTINE. It has 3 actual parameters (see also line 47).

Line 35:¶

The variable SDEV receives the value returned by the function VAR. VAR is not declared as an array but appears followed by a parameter list. It is therefore by default EXTERNAL, and a FUNCTION. It returns a single value, and the type of this value is implied in the normal way as for variables; in this case it is REAL because the letter V is not in the range I-N, nor does it appear in an IMPLICIT statement. There are three actual parameters X, N and K. The name SDEV is not declared, but is implicitly a variable of type REAL.

Line 36:¶

This line writes the results of the computations to unit 1 (the user’s terminal) according to the format at label 510. The first value written is the group letter, which is the substring taken from COLOUR starting and ending with the K'th (i.e., just one) character. The next value is the count of readings in each group taken from the array N. Then the average which was computed by the subroutine AVARAGE and left in the COMMON block. And finally the standard deviation as calculated by VAR and returned to SDEV in line 35.

Line 37:¶

The end of the DO-loop which starts at line 33. Once again, the CONTINUE statement is simply in order to place the statement label here.

Line 38:¶

A simple jump to avoid the error-handling routine to label 999 (line 44).

Line 39:¶

Another blank line of no significance.

Line 40:¶

Defines the format of the input records (used in line 14). There is a field of length 1 used as a literal character (A1); and a field of width 5 treated as a fixed-point number, with an implied position of the decimal point 2 digits from the right-hand end if no point is present explicitly.

Line 41:¶

Defines the output format, consisting of 6 separate fields. "1H" puts a blank in the first position.

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Since the user's terminal is being written to (see line 36), this first character is used as a "forms control character"; a blank means start on the next line. Then follow data formats of type character (A4), integer (I5), and fixed-point (F9.2). Next is a literal string and finally a field with an exponent (E10.3).

Line	Description
42	The start of the error handling. The statement label 900 is referred to by line 12.
43	An error message is written in free format to the user's terminal (unit 1). If an error in the OPEN statement is found, the IOSTAT status specifier indicates that an error code should be stored in the variable IERNAM. This is then written out by means of this WRITE statement.
44	A CONTINUE statement to hold the position of label 999.
45	An END statement marks the end of this program unit. The lines 1 to 45 could be compiled as a separate job.
46	Insignificant blank line.
47	A new program unit is started. It is a SUBROUTINE with the name AVRAGE and uses 3 dummy arguments called X, N, and K.
48	A COMMON block is defined called SHARE, containing one variable called AV. (The name SHARE is what connects this COMMON block with the one in the other program units 3 (lines 6 and 59).)
49	Declare X and N to be arrays. Since they are dummy arguments, the last upper bounds can be left free; this is what the * means.
48-49	There are no type statements here, so all variables will take the implicit types defined by their initial letters. In this program unit there are no IMPLICIT statements, therefore only the I-N rule is used. (Compare with line 9. Note that line 2 is no longer valid. Its range stopped with the END at line 45.)
50	Initialize the REAL variable R to zero.
51-53	A DO-loop to add up the N(K) values in X from X(K,1) to X(K,N(K)). The sum is accumulated in the variable R.

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Line	Description
54	Compute the average and place it in the variable AV, in the COMMON block where it is available to the other program units.
55	Terminate this program unit. When program execution reaches this point, it returns to where the program unit was called from and continues from there. (In this example there is only one point where a CALL statement is used, line 34.)
56	Another blank line.
57	VAR is declared to be the symbolic name of a FUNCTION which returns a REAL value and uses 3 dummy arguments called V, M, and J. By comparing the call in line 35 with this definition, it can be seen that the dummy argument V is a reference to the actual argument X, similarly that M refers to N, and J to K.
58-59	The same comments apply as for lines 48-49.
60	Initializes the return value to zero, VAR being the name of this FUNCTION.
61-63	A DO-loop to sum the squares of deviations for the J'th group. Note that it is assumed that AV has been set before the function is invoked.
64	An extraction of the square root completes the evaluation of the standard deviation. SQRT is an intrinsic function and here the actual argument is an expression. In this expression, the numerator is REAL, but the denominator is of type INTEGER, so it is converted to REAL before the division is done.
65	The END of this program unit. When the execution comes here, the value in VAR is taken as the value of the function and is sent back to the program unit that called the function.

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DATA TYPES, CONSTANTS, VARIABLES, ARRAYS AND SUBSTRINGS¶

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2.1 DATA TYPES¶

There are six data types defined in ANSI FORTRAN 77:

INTEGER
REAL
DOUBLE PRECISION
COMPLEX
LOGICAL
CHARACTER

In ND FORTRAN, there are further types:

INTEGER*1 (ND-500 only), INTEGER*2, INTEGER*4
DOUBLE INTEGER
REAL*4, REAL*6
REAL*8
COMPLEX*8, COMPLEX*12
COMPLEX*16, DOUBLE COMPLEX
LOGICAL*1 (ND-500 only), LOGICAL*2, LOGICAL*4
NUMERIC (ND-500 only)

These are fully described in Section 3.4 on page 54.

Each type has its own internal representation; for storage mapping see Appendix E. Appendix E also describes the default data types for the ND-100 and the ND-500.

2.1.1 Type rules for identifiers¶

A symbolic name identifying a constant, variable, array, external function, or statement function can have its type declared in a Type statement, see Section 3.4 on page 54. In the absence of an explicit declaration in a Type statement, the type is implied by the first letter of

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The name. A first letter of I, J, K, L, M, or N implies type integer and any other letter implies type real, unless an IMPLICIT statement is used to change the default implied type, see Section 3.5 on page 61.

The data type of an array element name is the same as the type of its array name. The data type of a function name is the type of the data item supplied by the function reference in an expression.

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2.2 CONSTANTS¶

A constant is an arithmetic constant, logical constant, or character constant. Constants do not change their value during execution of the object program. A PARAMETER statement enables a constant to be given a symbolic name, see Section 3.6. on page 63.

The value range for each type of constant is not specified in the ANSI FORTRAN 77 standard, and varies according to machine implementation. The ranges given below for ND FORTRAN apply to the ND-100 unless otherwise noted.

2.2.1 Integer constants¶

The form of an integer constant is an optional sign followed by a string of digits.

In ND FORTRAN, integers have either the type INTEGER2 or INTEGER4, see the Type statement (Section 3.4 on page 54). On the ND-500, the default integer type is INTEGER4, and on the ND-100, it is INTEGER2. These defaults can be changed by the DEFAULT command, see Section 14.24.1 on page 293.

The values must lie between -2147483648 and +2147483647 inclusive. If the number lies within the inclusive range: -32768 to +32767 and the number of digits used is 5 or less, then the data type is the default INTEGER type. Otherwise it is INTEGER*4.

For example:

Number	Type
0	INTEGER
32000	INTEGER
-127	INTEGER
1234567	INTEGER*4
-98765	INTEGER*4
000002	INTEGER*4

An integer data item is always an exact representation of an integer value.

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In ND FORTRAN, integers can be represented as octal numbers. These are a string of digits in the range 0 to 7 inclusive, followed by the letter B. Octal numbers must be unsigned and are stored as positive numbers.

The values must lie in the range 0 to 37777777777B. If the number lies within the range 0 to 177777B and the number of digits used is 6 or less, then the data type is the default INTEGER. Otherwise it is INTEGER*4.

For example:

Number	Type
1B	is INTEGER
123456B	is INTEGER
345670B	is INTEGER*4 (> 177777B)
000002B	is INTEGER*4 (> 6 octal digits used)

In ND FORTRAN, an integer constant may be written as a hexadecimal constant. This is a string of hexadecimal digits starting with a decimal digit and ending with a X.

For example:

Number	Type
0A0X
1ABCX

2.2.2 Real constants¶

The form of a basic real constant is an optional sign, an integer part, a decimal point, and a fractional part, in that order. Both the integer part and the fractional part are strings of digits; either of these parts may be omitted but not both.

A real exponent consists of the letter E followed by an optionally signed integer constant. A real exponent denotes a power of ten.

A real constant takes any of the forms:

Basic real constant.
Basic real constant followed by a real exponent.
Integer constant followed by a real exponent.

The value of a real constant containing a real exponent is the product of the constant preceding the E and the power of ten indicated by the integer following it.

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In ND FORTRAN, the absolute value of a real constant must be zero or lie between 10 ** -76 and 10 ** +76.

With the ND-500 and the optional 32-bit floating-point hardware on the NORD-10 and ND-100, all intermediate results during the execution of a program must also lie within this range, the accuracy being 6-7 decimal digits. The 48-bit floating-point hardware on the ND-100 can allow the range to extend from 10 ** -4932 to 10 ** 4932, with an accuracy of 9 digits, although for consistency and compatibility the range of real constants is restricted as before to 10 ** +76. This limit is also imposed on output values.

Examples of real constants are:

0.
3.1415927
-728.998
-.1
10E43
0.2718283E+1
1557.4077E-3
+1.E-10

A real value is an approximation to the actual value of a mathematical expression.

2.2.3 Double-precision constants¶

The form of a double-precision exponent is the letter D followed by an optionally signed integer constant. The exponent denotes a power of ten. A double-precision exponent is identical to a real exponent apart from the use of a D instead of an E.

A double-precision constant can take one of the forms:

Real constant without an exponent part followed by a double-precision exponent.
Integer constant followed by a double-precision exponent.

The value of a double-precision constant is the product of the constant preceding the D and the power of ten indicated by the integer which follows it.

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In ND FORTRAN, the range of values of double-precision data items is the same as for real data items, but the accuracy of the approximation is greater, being 16 decimal digits.

Examples:

2.302585092994046D0
-.1020
+123.40-04
0.123456789012345678901234567890D+21

Note that more digits than those of the accuracy limit may be written, the value of the constant being suitably approximated.

The range of double-precision exponents is -76 to +76.

2.2.4 Complex constants¶

The form of a complex constant is a left parenthesis followed by an ordered pair of real or integer constants separated by a comma, and followed by a right parenthesis. The first constant of the pair is the real part of the complex constant and the second is the imaginary part.

For example:

(0, 1)
(0.0, 1.0)
(3.1415927, 0)
(2.71828, 1.0E10)
(-1, +2.3E-1)

In ND FORTRAN, a COMPLEX*16 constant is written as a parenthesised pair of integer, real, or double precision constants, at least one of which is double precision.

For example:

(0, 1.D0)
(3.141590-1, 1.4142D+1)

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2.2.5 Logical constants¶

The forms and values of a logical constant are:

FORM	VALUE
.TRUE.	true
.FALSE.	false

In ND FORTRAN, the default data type of a logical constant depends on the computer. Thus:

ND-500 uses LOGICAL*4
NORD-10 and ND-100 use LOGICAL*2

However, the default may be changed by the DEFAULT command, see Section 14.24.1 on page 293.

2.2.6 Character constants¶

The form of a character constant is an apostrophe followed by a string of characters followed by an apostrophe. The string may contain any ASCII characters except CR (octal 15), LF (octal 12) or HT (octal 11).

The delimiting apostrophes are not part of the data item. Embedded apostrophes are represented by two consecutive apostrophes without intervening blanks. In a character constant, embedded blanks between the delimiting apostrophes are significant.

The length of a character constant is the number of characters between the delimiting apostrophes, except that each pair of consecutive apostrophes counts as a single character. The delimiting apostrophes are not counted. The length of a character constant must be greater than zero.

However, in ND FORTRAN, a string of characters may be of length zero.

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Examples¶

String as Written	Value
'ABC'	ABC
'I AM GREAT'	I AM GREAT
'I'M THE GREATEST'	I'M THE GREATEST
	empty (ND FORTRAN extension)

See Appendix E for the internal representation of character strings.

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2.3 VARIABLES¶

A variable is a data item having both a name and a type. Its value can be changed during the execution of a program.

Its name is a symbolic name and its type can be optionally specified by the appearance of the symbolic name in a Type statement. Otherwise its type is implied as being INTEGER or REAL by the first letter of its name, (see Section 2.1.1 on page 25), unless this is overridden by use of the IMPLICIT statement.

During the execution of a program, a variable may contain a defined or an undefined value. Before a value has been assigned to it, a variable will contain an undefined value, and any reference to it will produce an unpredictable result.

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2.4 ARRAYS¶

An array is an ordered set of data identified by an array name. Array names are symbolic names which must conform to the rules given in Section 1.3 on page 6.

The number of data items (or elements - see Section 2.4.1 on the next page) in an array is given by an array declarator having the form:

| a (d [, d] ...) |

where

a is the symbolic name of the array, and
d is a dimension declarator, the number of these specified being equal to the number of dimensions of the array.

The form of the dimension declarator is:

| [ d₁ : ] d₂ |

where

d₁ is the lower dimension bound
d₂ is the upper dimension bound.

The lower and upper dimension bounds are arithmetic expressions and are described in Section 3.1 on page 43.

Examples of array declarators are:

TABLE ( 2, 3, 4 )
ARRAY ( M1 : M2, M3 : M4 )

The size of an array is equal to the product of the sizes of the dimensions specified for that array by its array declarator. Thus, in the first of the above examples the array size would be 2x3x4 = 24. The size of an array is equal to the number of elements it contains.

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2.4.1 Array elements¶

Each item of data in the array is known as an array element. An array element name, by which an array element is referenced, is the array name qualified by a subscript. The form of an array element name is:

a (s [, s] ...)

where
- a is the array name, and
- ( s [, s] ... ) is a subscript where each s is an integer expression, referred to as a subscript expression.

A subscript expression can contain array element references and function references. The number of subscript expressions in the subscript must equal the number of dimensions declared for the array (see above).

Examples of array element names are:

TABLE ( I/K ** 2, L )  
ARRAY1 ( I + ARRAY2 (J*K, L ), M )

In ND FORTRAN, reference to a multi-dimensioned array may also be made as though it were an array of only one dimension. In this case, the array element referenced is given by the order in which the array elements are stored, see Section 2.4.2 on the next page. The subscript of the first element being the lower bound of the first dimension.

2.4.2 Order of stored array elements¶

The elements of an array are arranged in storage in ascending order with the value of the first subscript varying most rapidly. For example, elements of the array:

I ( 2, 3 )

are stored in the order:

I (1,1), I (2,1), I (1,2), I (2,2), I (1,3), I (2,3)

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2.4.3 Adjustable Arrays¶

An adjustable array has an adjustable array declarator, i.e. one having dimension declarators containing variable names.

Note that adjustable arrays may only be used for dummy argument declarations within subprograms, see Section 11.1 on page 214.

2.4.4 Assumed-Size Arrays¶

An assumed-size array is a constant array declarator or an adjustable array declarator, except that the upper dimension bound of the last dimension is an asterisk. The asterisk means that there is no declared upper limit of the array index. This does not change the requirement that the dummy argument must be wholly contained within the actual argument.

Note that assumed-size arrays may only be used for dummy argument declarations within subprograms, see Section 11.1 on page 214.

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2.4.5 Actual and dummy array declarators¶

Each array declarator is either an actual array declarator or a dummy array declarator.

An actual array declarator is one in which each of the dimension bound expressions (see Section 3.1 on page 43) is an integer constant expression. A dummy array declarator on the other hand, may be a constant array declarator, an adjustable array declarator or an assumed-size array declarator.

For more detailed descriptions, see Section 10.1 on page 214.

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2.5 CHARACTER SUBSTRINGS¶

A character substring is a contiguous portion of a character variable or character array element. The name of the substring may be referenced and have values assigned to it.

The substring name can take the forms:

v([e₁]:[e₂])

or

a(s[,s]...)([e₁]:[e₂])

where

Symbol	Description
`v`	is a character variable name.
`a(s[,s]...)`	is a character array element name.
`e₁` and `e₂`	are each integer expressions called substring expressions.

e₁ indicates the leftmost character position of the substring and e₂, the rightmost. For example, A(2:4) specifies the characters in positions 2 through 4 of the character variable A, while B(4,3)(1:6) specifies characters in positions 1 through 6 of the character array element B(4,3).

e₁ and e₂ must be within the limits: 1 ≤ e₁ ≤ e₂ ≤ maximum string strength

If e₁ exceeds the maximum string length, results are unpredictable.

If e₁ is omitted, a value of 1 (one) is assumed for it.

If e₂ is omitted, then its assumed value is that of the length of the character variable or array element. Both e₁ and e₂ may be omitted.

A substring expression may be any integer expression. It can contain array element references and function references.

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In ND FORTRAN there are two special values to note:

If e₁ is a constant expression whose value is -1, then it is interpreted as the position of the first non-blank character in the string.
If e₂ is a constant expression whose value is -1, then it is interpreted as the position of the last non-blank character in the string.

Thus, A(-1:-1) strips off leading and trailing blanks.

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CHAPTER 3¶

SPECIFICATION STATEMENTS¶

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FORTRAN specification statements specify storage allocation, type characteristics, and data arrangement. The different specification statements are:

DIMENSION
EQUIVALENCE
COMMON
Type statements
IMPLICIT
PARAMETER
EXTERNAL
INTRINSIC
SAVE
ASSEMBLY

All specification statements are non-executable.

3.1 THE DIMENSION STATEMENT¶

The DIMENSION statement provides the symbolic names and dimension specifications of arrays. Its form is:

| DIMENSION ad [, ad]... |

where
each ad is an array declarator of the form a(d,[ , d]...), see Section 2.4, on page 34.
Note that array declarators may also appear in COMMON statements and Type statements.

Each a appearing in a DIMENSION statement is the symbolic name of an array in the same program unit. Each d is a dimension declarator, and the number of dimensions of the array is the number of dimension declarators in the array declarator. The minimum number of dimensions is one and the maximum is seven.

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Note that in ND FORTRAN, the upper limit on the number of dimensions in an array is not applicable, except that arrays with more than 7 dimensions cannot be handled by the Symbolic Debugger.

The form of a dimension declarator is also given in Section 2.4, on page 34. Each dimension may be expressed as having two bounds, a lower and an upper, separated by a colon. The value of either bound may be positive, negative, or zero. If only the upper bound is given, then the value of the lower bound is one.

Dimension bounds are arithmetic expressions in which all constants (or their symbolic names) and variables are of type integer. The upper dimension bound of the last dimension may be an asterisk. The array declarator containing an asterisk in its last dimension bound may or may not be adjustable, see Section 2.4.3, on page 36. In an adjustable array, those dimension declarators that contain a variable name are called adjustable dimensions.

For example, in the statement:

DIMENSION PAGE (60), PROF (10, 12)

the array PAGE has 60 elements and 1 dimension. PROF is a two-dimensional array whose total size is:

10 x 12 = 120 elements

The statement:

DIMENSION TABLE (-1 : 10, 0 : 9)

defines a two-dimensional array called TABLE. The first subscript may vary from -1 to 10 (i.e., 12 values) and the second subscript varies from 0 to 9 (i.e., 10 values) giving a total size of 120 elements.

The following code:

SUBROUTINE SUB (A, ROWS, COLS)
INTEGER ROWS, COLS
DIMENSION A (ROWS, COLS)

defines a dummy argument as an adjustable array whose size is given by further dummy arguments.

For example, if ROWS = 4 and COLS = 5 on one entry to SUB, then the size of A is 4 x 5 = 20 elements with the

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Bounds of 4 and 5 remaining constant for this invocation, even though ROWS or COLS may receive new values during it. If, when it is called next time, ROWS = 3 and COLS = 2, then these bounds will hold for this new invocation.

In the next example:

SUBROUTINE CALC (TAB)
COMMON/CM/LEN
DIMENSION TAB (0 : LEN*(LEN + 1)/2, *)

TAB is an assumed-size array. The first upper bound is an integer expression, and the second upper bound is left free. Note that in these two last cases the bounds of the arrays are redetermined each time the subroutine is invoked, but that they remain fixed throughout each invocation.

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3.2 THE EQUIVALENCE STATEMENT¶

The EQUIVALENCE statement is used to specify that storage is shared by two or more variables, arrays, or character substrings.

An EQUIVALENCE statement has the form:

EQUIVALENCE (list) [, (list)] ....

Each list must contain at least two names. Names of dummy arguments are not allowed. Any subscript or substring expression in the list must be an integer constant expression.

If equivalenced items are of different data types, no type conversion is performed.

Example:

INTEGER*4 INT4
LOGICAL*4 LOG4
LOGICAL*2 LOG2
DOUBLE PRECISION RL8
EQUIVALENCE (INT4,LOG4),(LOG2,RL8)

The first pair of variables in the EQUIVALENCE statement, INT4 and LOG4, require exactly the same storage, they will overlap exactly. The second pair, require different amounts of storage, LOG2 requires 16 bits and RL8 requires 64 bits, but LOG2 and RL8 will begin at exactly the same place in memory.

There are restrictions on strict ANSI FORTRAN 77 due to the architecture of the NORD-10 and ND-100 machines. The reader should consult Appendix E for details. These restrictions are not applicable to the ND-500 or the NORD-10 and ND-100 with 32-bit floating-point hardware. Storage mapping is fully described in Appendix E.

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3.2.1 Array Names and Array Element Names¶

If an array element name occurs in an EQUIVALENCE statement, the number of subscript expressions must be the same as the number of dimensions specified in the array declarator for that array name. The use of an array name unqualified by a subscript in an EQUIVALENCE statement has the same effect as specifying the first element of the array.

3.2.2 Character Variables in EQUIVALENCE Statements¶

Items of type CHARACTER may be equivalenced only with other items of type CHARACTER.

Example:

CHARACTER A*4, B*4, C(2)*3
EQUIVALENCE (A, C(1)), (B, C(2))

The sharing of storage can be illustrated as follows:

02	03	04	05
A
	B
	C(1)	----	C(2)

In ND FORTRAN, the restriction on equivalencing CHARACTER only with CHARACTER is lifted. However, an arithmetic or logical item may not begin on an odd byte boundary on the ND-100, but the following is acceptable:

INTEGER K
CHARACTER*10 C
EQUIVALENCE (K, C (2 : 3))

since C can start at an odd byte so that K will start at an even byte.

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However:

INTEGER K, N
CHARACTER*10, C
EQUIVALENCE (K, C (1 : 2)), (N, C (2 : 3))

is not allowed, since there is no way of avoiding one of either K or N starting at an odd byte.

On the ND-500, this situation produces an extension message, not an error.

3.2.3 Restrictions on EQUIVALENCE Statements¶

An EQUIVALENCE statement must not specify that consecutive storage units are to be nonconsecutive as in:

REAL A (2)
DOUBLE PRECISION D(2)
EQUIVALENCE (A (1), D (1)), (A (2), D (2))

Nor may the same storage unit be specified more than once in a storage sequence, as in:

DIMENSION A (2)
EQUIVALENCE (A (1), B), (A (2), B)

However, there are several ways of specifying essentially the same equivalence information.

For example:

REAL A (20), B (10)
EQUIVALENCE (A (1), B (1)), (A (2), B (2))

Also, more than one list can refer to the same storage unit as in:

EQUIVALENCE (A,B,C), (A,D), (B,E,F), (C,G), (E,H)

which is the same as:

EQUIVALENCE (A,B,C,D,E,F,G,H)

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3.3 THE COMMON STATEMENT¶

The COMMON statement enables storage to be shared by different program units. This allows the program units to define and reference data without using arguments.

The form of the statement is:

| COMMON [/|cb|/] list[[,]/|cb|/|list|]

where

cb	is a COMMON block name
list	is a list of variable names, array names, and array declarators.

If the COMMON block name is omitted, the blank COMMON block will be used. If the first COMMON block name is omitted, the first two slashes are optional.

In each COMMON statement, items whose names appear in a list are declared to be in the immediately preceding COMMON block. If the first COMMON block name is omitted, then the items in the first list appear in blank COMMON.

Any COMMON block (including blank COMMON) may occur more than once in one or more COMMON statements within a program unit. The list following each successive appearance of the same COMMON block name is treated as a continuation of the list for that COMMON block.

Only one appearance of a symbolic name as a variable name, array name, or array declarator is permitted in all such lists within a program unit.

Dummy arguments must not appear in the list.

If a character variable or a character array is in a COMMON block then all items in the block must be of type character.

In ND FORTRAN, the mixing of entities of character and non-character data types in one COMMON block is allowed.

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3.3.1 COMMON Block Storage Sequences¶

During compilation of a source program, a storage sequence is formed for all items in the lists for a particular COMMON block. The order of the sequence is the same as the order of appearance of the lists. The sequence is further extended to include the storage for any storage sequence associated with it by equivalence association.

Storage sequences of all COMMON blocks with the same sequences have the same first storage unit. The storage sequences of all blank COMMON blocks also have the same first storage unit as each other. This results in the association of data in different program units.

For example, with the following code:

PROGRAM MAIN
COMMON / CM / MA, MB, MC
......
END
SUBROUTINE SUB
COMMON / CM / NA, NB, NC
......
END

MA and NA will share the same storage, as will the pairs MB, NB and MC, NC.

For details on the amount of storage occupied by
each variable and the way in which COMMON blocks are
mapped, see Appendix E.

3.3.2 Differences between Named COMMON and Blank COMMON¶

COMMON blocks of the same name must have the same size wherever they appear. Blank COMMON blocks may be of different sizes.

Items in named COMMON blocks may be initially defined by a DATA statement in a BLOCK DATA subprogram.

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Note that in the ANSI FORTRAN 77 standard, initialization of named COMMON blocks is restricted to BLOCK DATA subprograms and blank COMMON blocks cannot be initialized by DATA statements.

In ND FORTRAN both named and blank COMMON blocks may be initialized in any program unit.

Execution of RETURN and END statements can cause items in named COMMON blocks to become undefined but not items in blank COMMON.

In ND FORTRAN, items in COMMON blocks retain their values between calls, irrespective of whether they are named or not.

3.3.3 Restrictions on COMMON and EQUIVALENCE¶

An EQUIVALENCE statement must not cause the association of the storage of two different COMMON blocks in the same program unit. Furthermore, EQUIVALENCE association must not cause storage extension to precede that of the storage of the first item in a COMMON statement.

For example:

COMMON / X / A
REAL B (2)
EQUIVALENCE (A, B (2))

is not permitted.

3.3.4 COMMON Blocks in APT¶

In ND FORTRAN for the NORD-10 and ND-100, a COMMON block can be placed at a user-defined location in the APT (Alternative Page Table). When doing this, all other data areas will reside on the NPT (Normal Page Table) along with the program code. The user has most of the responsibility for setting access to the APT correctly.

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Such a COMMON block is defined by naming the block in the following way:

*n

where
n is the address in the APT where the block should start. n must be a decimal or octal integer constant, not a symbolic name.

For example:

COMMON/*1000B/A, B, C

Places A, B and C in the APT from octal address 1000.

Variables in APT COMMON cannot be used as freely as other variables, due to the difficulties of addressing them. They are restricted to the following uses:

In expressions
On the left of assignment statements
As actual arguments to subroutines and functions, if they are simple variables or array elements
In WRITE and READ statements (but not arrays)
Any data type, but not character

The user must set the alternative page table before an APT COMMON is accessed, by:

CALL ALTON (n)

where
n is the page table to use. (See also the SINTRAN Reference Manual, ND-60.128.4.)

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Before using any of the file subsystem monitor calls (e.g. RFILE), the APT must be disabled by:

CALL ALTOF

and then reinstated by:

CALL ALTON (n)

as before.

Use of I/O through the normal FORTRAN statements READ, WRITE, PRINT, OPEN, CLOSE, BACKSPACE, ENDFILE and REWIND is automatically protected.

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3.4 TYPE STATEMENTS¶

A Type statement is used to override or confirm an implicit type. It may also provide dimension information.

The appearance of the name of a variable, array, statement function, external function, or a constant in a Type statement, specifies the data type for that name for all occurrences of it in a program unit.

The name of a main program, subroutine, or block data subprogram must not be used in a Type statement.

3.4.1 INTEGER, REAL, DOUBLE PRECISION, NUMERIC, COMPLEX and LOGICAL Type Statements¶

These statements have the form:


type var [/value/] [,var[/value/]]...

where

type is one of INTEGER, REAL, DOUBLE PRECISION, NUMERIC (fw,sc), COMPLEX and LOGICAL.

NUMERIC (fw,sc) is also used to specify entities of packed decimal format also known as BCD (Binary Coded Decimal). This is a fixed format, where fw (field width) specifies the number of digits in the entity, and sc (scaling factor) specifies the number of digits to the right of the decimal point. This type should be used mainly when mixing routines within COBOL and FORTRAN.

var is a variable name, array name, array declarator, function name, dummy-procedure name, or the symbolic name of a constant.

value is a constant, a symbolic name of a constant or INTRINSIC functions (see Section 5.1.2 on page 85 and Section 5.4.1 on page 95) with constant

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Expressions as parameters. If var is an array, then value means a list of values, one for each element of the array; if the list contains less values than required for the entire array, the rest of the array will be initialized to zero; the list may contain a constant or symbolic name of a constant prefixed by a repetition factor (followed by an asterisk, as in the DATA statement). This is an ND FORTRAN extension.

In ND FORTRAN, additional types are allowed. The implications for the use of storage are fully explained in Appendix E.

The new types are:

INTEGER*1    occupies 1 byte of storage (ND-500 only)
INTEGER*2    occupies 2 bytes of storage
INTEGER*4    occupies 4 bytes of storage
DOUBLE INTEGER occupies 4 bytes of storage

The above types behave in the same way as type INTEGER. In particular, they can be used in expressions for subscripts etc. DOUBLE INTEGER and INTEGER*4 are identical in all respects.

Type	Description
REAL*4	the same as REAL
REAL*6	the same as REAL
REAL*8	the same as DOUBLE PRECISION
NUMERIC (fw,sc)	(ND-500 only)
COMPLEX*8	the same as COMPLEX
COMPLEX*12	the same as COMPLEX
COMPLEX*16	COMPLEX values with DOUBLE PRECISION accuracy
DOUBLE COMPLEX	the same as COMPLEX*16
LOGICAL*1	occupies 1 byte of storage (ND-500 only)
LOGICAL*2	occupies 2 bytes of storage
LOGICAL*4	occupies 4 bytes of storage

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During the evaluation of an arithmetic expression, the order of implied conversion is:

INTEGER*1
INTEGER*2
INTEGER*4
REAL
DOUBLE PRECISION
NUMERIC (fw,sc)
COMPLEX
DOUBLE COMPLEX

The CMPLX intrinsic function applied to a DOUBLE PRECISION argument gives a DOUBLE COMPLEX result. It should be used to retain accuracy when mixing DOUBLE PRECISION and COMPLEX operands.

There is an equivalent hierarchy for logical expressions. The order of implied conversion is:

LOGICAL*1
LOGICAL*2
LOGICAL*4

3.4.2 CHARACTER Type Statement¶

The form of this statement is:

| CHARACTER [*length [,]] name [/value/][,name [/value/]]... |

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where name can take the form of:

v [*length]

or

a [(d)][*length]

v is a variable name, function name, dummy procedure name, or the symbolic name of a constant.
a is an array name.
a (d) is an array declarator.
length is the length (number of characters) of the associated name. It is one of the following:
- An unsigned, non-zero, decimal integer constant.
- An integer constant expression within parentheses and having a positive value.

In ND FORTRAN, if the expression is only the name of a symbolic constant, the surrounding parentheses can be omitted.

For example, in ANSI FORTRAN 77:

PARAMETER (LEN = 10)
CHARACTER C*(LEN)

could be written in ND FORTRAN as:

PARAMETER (LEN = 10)
CHARACTER C*LEN

In ND FORTRAN also, if the expression is not of type INTEGER, it will be converted to type INTEGER.

An asterisk in parentheses, (*).

value is a constant, a symbolic name of a constant or the INTRINSIC function CHAR with a constant expression as parameter. If name is an array, then value means a list of values, one for each element of the array; if the list contains fewer values than required for the entire array, the rest of the array will be

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initialized to zero; the list may contain a constant or symbolic name prefixed by a repetition factor (followed by an asterisk, as in the DATA statement). This is an ND FORTRAN extension.

A length specification immediately following the word CHARACTER applies to each item in the statement without a length specification of its own. If this initial length specification does not appear, then the default length in the example on page (PREVIOUS) is one.

For example:

CHARACTER*3 A, B*4, C

defines A, B and C as character strings of lengths 3, 4 and 3 respectively. Also:

CHARACTER A, B*4, C

gives A, B and C lengths of 1, 4 and 1 respectively.

A length specification must be an integer constant expression except for external functions, dummy arguments of external procedures, or character constants having a symbolic name.

If the length of a dummy argument is declared as (*), then it assumes the length of the associated actual argument for each reference of the subroutine or function. (When the associated actual argument is an array name then the length of an element of the array is assumed.)

For example:

SUBROUTINE S (C)
CHARACTER C*(*) 
.....
END

PROGRAM MAIN
CHARACTER A*4, B*9
CALL S(A)
CALL S(B)
.....
END

In the above code, the first time S is called, the dummy argument C identifies with A, and so has a length of 4; the second time, it takes the length of B, i.e., 9.

If the length of an external function is declared in a

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function subprogram as (*) then the function name must appear in a FUNCTION or ENTRY statement in the same subprogram. On execution of such a function reference, the assumed length is that specified in the referencing program.

The length given for a character function in a referencing program must be an integer constant expression that agrees with the length given in the specifying subprogram.

For example:

FUNCTION NAME
CHARACTER *\(*) NAME
.......
NAME = TAB (I)
RETURN
END
SUBROUTINE PERSON
EXTERNAL NAME
CHARACTER NAME*25, PN*25
.......
PN=NAME ()
.......
END
SUBROUTINE FIRM
EXTERNAL NAME
CHARACTER*35 NAME, FN
.......
FN=NAME ()
.......
END

In the above, when NAME is called from PERSON, its length is 25. When it is called from FIRM, its length is 35. Within both PERSON and FIRM, NAME must be declared with a constant length and not with an asterisk (*).

If a character constant with a symbolic name has its length declared as (*), then the constant assumes the length of its corresponding constant expression in a PARAMETER statement.

For example, in the code:

CHARACTER HEAD *\(*\)
PARAMETER (HEAD = ' TOTALS-BY-MONTH')

the length of HEAD becomes 15.

A character statement function or the character dummy argument of a statement function must have a length

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which is an integer constant expression.

For example, if we have:

CHARACTER DIGITS*10, MNAMS*50
CHARACTER*3 MONTH, DAY*2, DATE*6, DD*2, DM*3
DATA DIGITS/'0123456789'/, MNAMS/'JAN FEB MAR...DEC'/
DAY (I) = DIGITS (I/10+1:I/10+1)//DIGITS (MOD(I,10)+1:MOD(I,10)+1)
MONTH (I) = MNAMS (3*I-2:3*I)
DATE (DD, DM) = DD // '-' // DM

then the statement functions DAY, MONTH and DATE must be of known fixed length, as must the dummy arguments of DATE, i.e., DD and DM.

In ND FORTRAN there are restrictions on the maximum length of items of type CHARACTER. On the ND-500, the maximum is 32767, and on NORD-10/ND-100 it is 2047. The upper limits apply to all CHARACTER items, including the maximum lengths of all CHARACTER expressions that are not assigned (i.e., used as actual parameters or as operands to relational operators).

See Appendix E for the internal representation of CHARACTER data.

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3.5 THE IMPLICIT STATEMENT¶

An IMPLICIT statement is used to change or confirm default implied data types, based on the initial letter of the symbolic name of a constant, variable, array, external function, or statement function.

The statement has the form:

| IMPLICIT type (a[,a]...) [,type(a[,a]....) ] |

where

type is one of INTEGER, REAL, DOUBLE PRECISION, NUMERIC (fw, sc), COMPLEX, LOGICAL or CHARACTER [* length].

In ND FORTRAN, type may also be one of the ND extensions, see Section 3.4 on page 54.

a is a single letter or range of single letters in alphabetical order. A range is denoted by the first and last letter of the range separated by a minus.

length is the length of a character item and must be either an unsigned, non-zero, integer constant, or a positive integer constant expression in parentheses. Its default value is one.

For example:

IMPLICIT COMPLEX (C)

ensures that all untyped names beginning with a C will be of type COMPLEX.

An IMPLICIT statement specifies a type for all:

variables
arrays
symbolic names of constants
external functions
statement functions

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based on the first letter of the name. The normal defaults for types can be expressed as:

IMPLICIT REAL (A-H, O-Z), INTEGER (I-N)

For example:

VARIABLE NAME	IMPLICIT VARIABLE TYPE
x123	REAL
horse	REAL
insect	INTEGER
c	REAL
J	INTEGER

An IMPLICIT statement does not change the type of any intrinsic function, and its scope is that of the program unit containing it.

Type specification by an IMPLICIT statement may be overridden in all cases by a type statement. An explicit type specification in a FUNCTION statement overrides an IMPLICIT statement for the name of that function subprogram. Note that the length is also overridden when a particular name appears in a CHARACTER or CHARACTER FUNCTION statement.

IMPLICIT statements must precede all other specification statements in a program unit except a PARAMETER statement. More than one IMPLICIT statement may be used in a program unit.

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3.6 THE PARAMETER STATEMENT¶

A PARAMETER statement is used to give a constant a symbolic name.

The form of a PARAMETER statement is:

PARAMETER (p = e [, p = e]...)

where

p is a symbolic name of a constant
e is a constant expression

The assignment to p is made according to the rules for the assignment statements, see Chapter 6.

When p is of type integer, real, double precision, or complex, then the corresponding expression must be an arithmetic constant expression. If p is of type character or logical, the corresponding expression must be a constant expression of type character or logical respectively.

p must not be defined more than once in a program unit. Furthermore, if it is not of default implied type, then its type must be specified by a Type statement or IMPLICIT statement prior to its first appearance in a PARAMETER statement.

If p is of type character and of length other than the default length of one, its length must be also defined prior to its first appearance in a PARAMETER statement.

For example, the following code:

PARAMETER (PI = 3.141593)
COMPLEX J
PARAMETER (J = (0.,1.), ROOT2 = 1.4142)
PARAMETER (RADIAN = 180/PI)

defines three REAL symbolic constants and one COMPLEX one.

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In the sequence:

PARAMETER (MAX = 100)
IMPLICIT REAL (M)
DIMENSION MATRIX (MAX, MAX)
PARAMETER (MAGFLD = 0.82)

the IMPLICIT statement does not apply to the PARAMETER statement that precedes it. Thus MATRIX and MAGFLD are both of type REAL but MAX is of default type (i.e., INTEGER).

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3.7 THE EXTERNAL STATEMENT¶

An EXTERNAL statement is used to identify an external or dummy procedure and to permit its symbolic name to be used as an actual argument.

The form of an EXTERNAL statement is:

EXTERNAL proc [,proc]...

where

| each proc | is the name of an external procedure, dummy procedure, or block data subprogram. |

When a name appears in an EXTERNAL statement it is declared to be an external procedure, dummy procedure, or block data subprogram name. If an external procedure name or dummy procedure name is used as an actual argument, it must appear in an EXTERNAL statement in the same program unit. A statement function name cannot appear in an EXTERNAL statement.

The name of an intrinsic function appearing in an EXTERNAL statement becomes the name of some external procedure, whereupon an intrinsic function of the same name cannot be referenced in the program unit.

Only one occurrence of a symbolic name is allowed in all of the EXTERNAL statements of a program unit.

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3.8 THE INTRINSIC STATEMENT¶

An INTRINSIC statement is used to identify the name of an INTRINSIC function and to permit the use of this name as an actual argument.

The form of this statement is:

| INTRINSIC fname [,fname]... |

where each fname is an INTRINSIC function name.

If a specific name of an INTRINSIC function is used as an actual argument, it must appear in an INTRINSIC statement in the same program unit. For the INTRINSIC function names which must not be used as actual arguments, see Section 11.2 on page 222.

If a generic function name appears in an INTRINSIC statement, it does not loose its generic property.

A symbolic name may only appear once in all of the INTRINSIC statements of a program unit and it must not occur in this unit in both an EXTERNAL and an INTRINSIC statement.

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3.9 THE SAVE STATEMENT¶

A SAVE statement retains the defined values of items after execution of a RETURN or END statement in a subprogram.

It has the form:

| SAVE [ a [,a ]...] |

where

each a is a named common block name preceded and followed by a slash, or a variable name, or an array name. (Dummy argument names, procedure names, and names of items in a common block must not appear.)

A SAVE statement without a list is treated as though it contained the names of all allowable items within the program unit. The appearance of a common block name preceded and followed by a slash has the effect of specifying all of the items in that block.

When a common block name occurs in a SAVE statement in a subprogram then it must occur in a SAVE statement in every subprogram in which the common block appears.

If a named common block appears in a SAVE statement of a subprogram, then the current value of items in the common block storage sequence when a RETURN or END statement is executed are made available to the next program unit specifying that common block.

If a named common block is specified in the main program unit, then the current values of the common block storage sequence become available to each subprogram specifying that common block; a SAVE statement in this program has no effect.

If a local item appearing in a SAVE statement but not in a common block is in a defined state when a RETURN or END statement is executed, then this item is defined with the same value at the next reference to the same subprogram.

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In ND FORTRAN, this statement is checked for valid syntax, but is otherwise ignored. If the REENTRANT compiler option is OFF or the FIXED-DATA-AREA compile option is ON, all variables are saved, and so the statement is redundant. If the REENTRANT option is ON or the FIXED-DATA-AREA compile option is OFF, all common variables are saved but other variables are not.

IMPORTANT:

Reentrant programs do not conform to the ANSI FORTRAN 77 standard if they contain SAVE statements referring to local variables.

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3.10 THE ASSEMBLY STATEMENT¶

This statement is an ND FORTRAN extension and is used to modify the calling sequence for EXTERNAL subroutines and functions.

The form of the statement is:

| ASSEMBLY name [,name]... |

Each name is the name of an externally-compiled routine or function, or the name of a dummy argument. The names cannot also appear in an EXTERNAL statement. They may be used either as subroutines or as functions, with the exception of character functions.

When these functions are called, their actual arguments must obey certain restrictions:

There can be no more than 4 of them.
They must be INTEGER*2 or non-character array names.

The statement is checked for syntax on the ND-500, but the names are then assumed to be EXTERNAL names or arguments.

The ASSEMBLY statement modifies the calling sequence to EXTERNAL program units on ND-100 programs. It can be used where the external routine is written in MAC, NPL, or PLANC with the SPECIAL option, see Appendix F for details of the calling sequences.

On the ND-500, the statement is exactly equivalent to an EXTERNAL statement.

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Chapter 4¶

The Data Statement¶

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THE DATA STATEMENT¶

A DATA statement is used to provide initial values for variables, arrays, array elements and substrings.

The form of a DATA statement is:

| DATA namelist/valuelist/ [[,] namelist/valuelist / ].. |

where

namelist is a list of names of variables, arrays, array elements, and substrings, together with implied DO lists.

valuelist consists of a list of constants and/or symbolic names of constants, each of which may be prefixed by a repetition factor.

In ND FORTRAN, valuelist may consist of some INTRINSIC functions with constant expressions as parameters (see Sections 5.1.2 on page 85, 5.2.1 on page 88 and 5.4.1 on page 95).

4.1 DATA STATEMENT RESTRICTIONS¶

Each namelist and valuelist must contain the same number of items. There is a one-to-one correspondence between the items in the two lists.

If an array name without a subscript appears in the list, then there must be one constant for each element of that array.

Initialization must not occur more than once for variables, array elements, or substrings.

Each constant value from the valuelist is used to initialize the corresponding element from the namelist according to the rules of a normal FORTRAN assignment statement, see Chapter 7 which starts on page 115.

In ND FORTRAN, DATA statements may precede other specification statements. However, in this case, the variables in the DATA statements must have their

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Examples of simple DATA statements:

DATA I/10/

This assigns a value of 10 to the integer variable I before execution of the program.

DATA PI/3.1415927/E/2.7182818/

is the same as

DATA PI,E/3.1415927, 2.7182818/

To initialize a 6-element array to the values 1, 2, 3, 4, 5, and 6, we may write:

REAL X(6)
DATA X/1, 2, 3, 4, 5, 6 /

To zero an array, the following could be used:

REAL STATS (10, 10)
DATA STATS /100*0./

For multidimensional array names, the implied order of elements is with the first subscript varying most rapidly. Thus:

DIMENSION A (3, 3)
DATA A/11, 21, 31, 12, 22, 32, 13, 23, 33/

will produce an array with the values:

A(1,1)=11, A(2,1)=21, A(3,1)=31, A(1,2)=12,...
and so on.

Note that replication factors can cut across name-list items. Thus:

DIMENSION A(8), B(8)
DATA A, B/1, 14*0, -1/

will set A(1) to 1, B(8) to -1, and all other elements of A and B to 0.

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4.2 IMPLIED DO IN A DATA STATEMENT¶

An implied DO list may appear in a DATA statement namelist, see Section 8.7 on page 135. It is written as:

(dlist, I = m₁, m₂ [, m₃])

where

dlist is a list of array element names.
dlist may contain other implied DO lists.
I is the name of an integer variable, here called the implied DO-variable.
m₁, m₂, m₃ and the subscripts in the dlist are each an integer constant expression or an integer expression containing only constants and the implied DO-variable.

An iteration count and the values of the implied DO-variable are established from m₁, m₂, and m₃ exactly as for a DO-loop, see Section 8.7, except that the iteration count must be positive.

For example:

To initialize the even elements of a one-dimensional array to +1, and the odd elements to -1, you may write:

DIMENSION SGN (20)
DATA (SGN (I), I=2, 20, 2)/10*+1/(SGN (I), I=1, 20, 2)/10*-1/

or to create a character string of alternating A's and B's:

CHARACTER C*40
DATA (C(2*K-1:2*K), K=1, 20)/20*'AB'/

To initialize only the diagonal elements of a square array:

DIMENSION Q (10, 10)
DATA (Q (N, N), N = 1, 10)/10*1.1/

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The default ordering of a two-dimensional array is by columns. To set data in by rows, you can write:

DIMENSION A(3,3)
DATA ((A (I,J),J=1,3)I=1,3)/11,12,13,21,22,23,31,32,33/

which will set up A as in the last example in the previous section. Note the ordering of the loops. The innermost one varies most often.

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Chapter 5¶

Expressions¶

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EXPRESSIONS¶

An expression is formed from operands, operators and parentheses. This chapter describes the formation, interpretation, and evaluation rules for the various types of expressions. These may be:

Arithmetic
Character
Relational
Logical

5.1 ARITHMETIC EXPRESSIONS¶

The simplest form of arithmetic expression is an unsigned arithmetic constant, symbolic name of an arithmetic constant, or an arithmetic type of variable, array element, or function reference.

Examples:

Expression	Description
99	(arithmetic constant)
IV	(integer variable)
TABLE (2,3,4)	(array element)
LOG (X+Y)	(function reference)

More complicated arithmetic expressions can be formed by using one or more arithmetic operands together with arithmetic operators and parentheses.

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Arithmetic Operators¶

The arithmetic operators are:

OPERATOR	MEANING
**	Exponentiation
/	Division
*	Multiplication
-	Subtraction (or negation)
+	Addition

All the above operators are binary, i.e. used with two operands. The - and the + are also available as unary, i.e. used with only one operand.

There is a precedence among the arithmetic operators which determines the order in which the operands are to be combined (unless the order is changed by the use of parentheses) as follows:

OPERATOR	PRECEDENCE
**	highest
* and /	intermediate
+ and -	lowest (unary and binary)

Within each precedence level, the order is assumed to be from left to right, except with exponentiation which is evaluated from right to left.

The arithmetic operands are:

unsigned arithmetic constants
symbolic names of arithmetic constants
arithmetic variables
arithmetic array elements
function references
arithmetic expressions enclosed in parentheses

or any of the above operands combined by arithmetic operators to form arithmetic expressions.

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Examples:¶

If X, Y, Z, A, and B are variables:

Expression	Description
X+Y	will form the sum of X and Y
X-Y	will subtract Y from X
X+Y+Z	will sum together X, Y, and Z
X+Y-Z	will add X and Y and then subtract Z from the result (see general notes below)
X*Y/Z	will multiply X and Y before dividing the result by Z (see general notes below)
X/Z*Y	will divide Z into X first, and then multiply the result by Y
X*Y+Z	will multiply X and Y and add Z to the result
Z+X*Y	will multiply X and Y and then add the result to Z; the order here is determined by operator precedences. * is performed first, followed by +, as in example 7
XYZ	will raise Y to the power of Z first, then X is raised to the power of this result
-A**2	Since the operator has precedence in this example, its operands will be combined first. Thus, the expression will be interpreted as: – (A 2).

In this example, it can be seen that expressions containing two consecutive arithmetic operators, such as A-B or A+-B, are not allowed. However, expressions such as A(-B) are permitted.

In ND FORTRAN, such juxtapositioning of signs is allowed when the second of them is a unary + or -. Thus, A+-B is evaluated as A+(-B), and X---Y as X-(-(-Y)) etc.

If the order dictated by the precedence rules is not the order required, then parts of an expression may be written within parentheses. Parts thus enclosed are then evaluated as a whole expression before being used as an operand.

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For example:

Expression	Description
X+Y/Z	will cause Y to be divided by Z before adding X to the result (precedence rules).
(X+Y)/Z	will ensure that X is added to Y before the result is divided by Z.
(X+Y)/(X+Z)	here X+Y and X+Z will be computed separately and then the result of X+Y will be divided by the result of X+Z. Note that in this case there is no stipulation as to whether X+Y or X+Z is evaluated first.

While the symbols +, -, *, /, and ** represent the usual mathematical operations, the reader should be aware that the underlying computing hardware has fixed limits as to the precision and accuracy of the representation of values and the results of operations. These are described for each machine in Appendix E.

Note that the order of operations on the computing hardware is such that the result would be mathematically exact if the hardware were mathematically precise. If a particular order of operations is vital for numerical accuracy, it is best to use parentheses to force the order.

For example:

Expression	Description
X+Y+Z	represents the sum of X, Y, and Z; the computation may add X to Y and then add Z, or it may add Y to Z and then add X, etc.
(X+Y)+Z	however, will ensure that X and Y are added together first, before adding Z to this result.

5.1.1 Interpretation of Results for Arithmetic Expressions¶

When the operator + or - operates on a single operand, the data type of the result is the same as that of the operand.

When an arithmetic operator operates on a pair of operands, then, except for exponentiation, the data type of the result is as follows:

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If the types of the two operands are the same, then the data type of the result will be the data type of these operands.

If the types of the two operands are different, the operand of lower data type (see below) is converted to the data type of the other operand. Thus, the higher order data type will be that of the result.

The hierarchical order of the data types is:

DATA TYPE	ORDER
integer	lowest
real
double precision
numeric
complex	highest

Note that the conversion takes place before the operation is performed, and that the operators are defined only for operands of equivalent type. The conversions are defined by the INTRINSIC functions REAL, DBLE, and CMPLX, see Section 11.2 on page 222.

For example:

If I, R, D, and C are variables of type INTEGER, REAL, DOUBLE PRECISION, and COMPLEX respectively, then:

the result of the expression I+I is of type INTEGER

I*R will cause I to be converted to type REAL before the multiplication, and the result is of type REAL

(D/I)+R will first cause conversion of I to DOUBLE PRECISION; then the division will occur, then R will be converted to DOUBLE PRECISION, and finally, the addition will take place giving a result of type DOUBLE PRECISION

D/I+R will have exactly the same effect as the previous example, since the precedence rule for operators implies that division occurs before addition

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R*C will produce a result of type COMPLEX
For the exponentiation operator, if the exponent (i.e., the right-hand operand) is of type integer, then the data type of the result is the same as that of the left-hand operand. Otherwise conversion takes place as given above for the case of two arithmetic operands.

For example:¶

If I and R are variables of data types INTEGER and REAL respectively, then:

I**I
has a result of type INTEGER
R**I
is an expression of type REAL, (but note that I is not converted here)
I**R
is of type REAL, and I is converted to REAL
R**R
is of type REAL

Note:¶

If the exponent is of type INTEGER, then exponentiation can be defined as repeated multiplications, so that every value of the base (i.e., left-hand operand) is admissible. (except zero if the exponent is negative.) But if the exponent is not of type INTEGER, A*B is defined as EXP(BLOG(A)), where EXP and LOG are the INTRINSIC functions described in Section 11.2 on page 222. In particular, note that LOG is not defined for negative values of its argument. It is important to realize that the difference in definition is dependent on the type of the exponent and not on its value.

Thus, (-3.0)(2.0) is an error, whereas (-3.0)2 is not.

In ND FORTRAN, there is one exception to the rule that if the right-hand operand with a ** operator is of type INTEGER then the result type is the same as the type of the left-hand operand. If the right-hand operand is INTEGER4 and the left operand is INTEGER2, then the result is INTEGER*4.

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5.1.2 Arithmetic Constant Expressions¶

An arithmetic constant expression is an arithmetic expression in which each operand is an arithmetic constant, a symbolic name of an arithmetic constant, or an arithmetic constant expression enclosed in parentheses. Any arithmetic operator is allowed; the ** operator is valid only if the exponent is of type INTEGER.

In ND FORTRAN, any of the following INTRINSIC functions, may be used:

MIN, MAX, MOD, ABS, ICHAR, NINT, ANINT, DIM, DPROD, CMPLX, CONJG, IMAG or LEN,

provided that all parameters are constant expressions.

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5.2 CHARACTER EXPRESSIONS¶

The simplest form of a character expression is a character constant or the symbolic name of one, or a character-type variable, array element, substring, or function reference. More complicated character expressions are formed by using one or more character operands together with the character operator and parentheses.

Evaluation of a character expression produces a character-type result.

The character operator is:

//

which represents concatenation. The result of 'AB' // 'CD' is 'ABCD'.

If a character variable is of unknown length, then there are certain restrictions on its use in character expressions, in that it can be used only in character assignment statements, and even then, only when it directly forms part of the final result.

For example:

If we have the following declarations:

SUBROUTINE SR(C)
CHARACTER C*(*) , A*100 , B*10

then C is of unknown length, i.e. its length is taken from the actual parameter.

You are allowed to write:

A = C//B

because the final result length is constrained by the length of A.

But you cannot write:

CALL X(C//B)

because the actual argument is an expression whose length is not constrained.

Similarly, the following expressions are allowed:

A = C (1:J) // C (1:N)
B = A (1:3) // C (4:7)
A = (C (1:N) // B) // (B (2:N) // C)

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but none of these expressions can be used as actual arguments, or as part of a relational expression (even though they may then form part of an assignment statement).

Note that a symbolic constant always has a known length since a declaration with length (*) means: use the length of the constant expression assigned to it by a PARAMETER statement.

For example:

CHARACTER ALPHA* (*)
PARAMETER (ALPHA = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ')

implies no restrictions on the use of ALPHA due to its length (*).

Character operands are:

character constants
symbolic names of character constants
character variables
character array elements
character substrings
character function references
character expressions enclosed in parentheses

or any combination of the above operands using the character operator.

A character expression is a sequence of one or more operands separated by the character operator, (concatenation operator, //). The evaluation is from left to right. Thus, the expression:

'AB' // 'CD' // 'EF'

is the same as:

('AB' // 'CD') // 'EF'

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5.2.1 CHARACTER Constant Expressions¶

A character constant expression is a character expression in which each operand is a character constant, the symbolic name of a character constant or a character constant expression enclosed in parentheses. The only operand allowed is the concatenation operator, //.

In ND FORTRAN, the INTRINSIC function, CHAR, may be used, provided that the parameter is a constant expression.

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5.3 RELATIONAL EXPRESSIONS¶

A relational expression is used to compare the values of two arithmetic expressions or two character expressions.

In ND FORTRAN, it is also possible to compare logical expressions for equality or non-equality.

Relational expressions may form part of logical expressions and, on evaluation, they produce a result of type logical, i.e. a value .TRUE. or .FALSE.

The relational operators are:

OPERATOR	MEANING
.LT.	Less than
.LE.	Less than or equal to
.EQ.	Equal to
.NE.	Not equal to
.GT.	Greater than
.GE.	Greater than or equal to

5.3.1 Arithmetic Relational Expressions¶

The form of an arithmetic relational expression is:

e₁ rel e₂

where

rel is a relational operator
e₁ and e₂ are each an integer, real, double precision, numeric or complex expression.

A complex operand is permitted only when the relational operator is .EQ. or .NE.

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Before the comparison is carried out, the operands are converted, if necessary, to make them of the same type. The rules are the same as those for the common arithmetic operators, see Section 5.1 on page 80.

For example:

If I, R, D, and C are variables of type INTEGER, REAL, DOUBLE PRECISION, and COMPLEX respectively, then:

I.LE.0 will give a value .TRUE. if I has the value zero.
R.GT.0 - 10 will yield .TRUE. if the value of R is greater than -10.
D.LT.R will convert R to DOUBLE PRECISION and the comparison will yield .TRUE. if the value of D is less than R.
1..LE.I will convert I to REAL since the constant 1. is REAL (note the extra dot).

For the relationship between arithmetic and relational operators, see Section 5.5 on page 96.

5.3.2 CHARACTER Relational Expressions¶

Character relational expressions have the form:

| e₁ rel e₂ |

where

rel is a relational operator
e₁ and e₂ are character expressions.

Note: e₁ is considered to be less than e₂ if its value precedes that of e₂ in the collating sequence (see Appendix A).

If the lengths e₁ and e₂ are unequal, then for comparison purposes the shorter string is extended to the right and filled with blanks.

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5.3.3 LOGICAL Relational Expressions¶

In ND FORTRAN, logical quantities can be compared by .EQ. and .NE. These operators have the usual precedence of relational operators and perform the usual function. If two logical expressions are both .TRUE. or both .FALSE., then comparing them with .EQ. will give .TRUE..etc.

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5.4 LOGICAL EXPRESSIONS¶

Evaluation of a logical expression produces a logical result, i.e. with a value of .TRUE. or .FALSE.

In its simplest form, a logical expression is a logical constant (or the symbolic name of one), or a logical variable, array element, function reference, or it can also be a relational expression.

More complicated expressions can be formed using one or more logical operands combined with logical operators and parentheses.

The logical operators are:

OPERATOR	MEANING
.NOT.	logical negation
.AND.	logical conjunction
.OR.	inclusive or
.EQV.	logical equivalence
.NEQV.	logical non-equivalence (exclusive or)

The operator .NOT. is unary, i.e. used with one operand. The other operators are binary, i.e. used with two operands.

The logical operators have a precedence order, i.e. the order in which operands are to be evaluated, unless this is changed by the use of parentheses.

OPERATOR	PRECEDENCE
.NOT.	highest
.AND.
.OR.
.EQV. or .NEQV.	lowest

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For example, in:

A .OR. B .AND. C

the .AND. operator has higher precedence than the .OR.; therefore the interpretation of the above expression is the same as the following:

A .OR. (B .AND. C)

The values of expressions involving the above operators is shown below, where X₁ and X₂ are logical operands:

X₁	.NOT. X₁
.TRUE.	.FALSE.
.FALSE.	.TRUE.

X₁	X₂	X₁ .AND. X₂	X₁ .OR. X₂
.TRUE.	.TRUE.	.TRUE.	.TRUE.
.TRUE.	.FALSE.	.FALSE.	.TRUE.
.FALSE.	.TRUE.	.FALSE.	.TRUE.
.FALSE.	.FALSE.	.FALSE.	.FALSE.

X₁	X₂	X₁ .EQV. X₂	X₁ .NEQV. X₂
.TRUE.	.TRUE.	.TRUE.	.FALSE.
.TRUE.	.FALSE.	.FALSE.	.TRUE.
.FALSE.	.TRUE.	.FALSE.	.TRUE.
.FALSE.	.FALSE.	.TRUE.	.FALSE.

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The logical operands are:

logical constants
symbolic names of logical constants
logical variables
logical array elements
logical function references
relational expressions
logical expressions enclosed in parentheses
or any of the above operands combined by logical
operators to form logical expressions.

For examples of how these combine with relational and arithmetic operators, see Section 5.5 on page 96.

The data type of the result of an operator which returns a logical result is LOGICAL.

In ND FORTRAN, the result is the default LOGICAL
data type, i.e. LOGICAL2 for the ND-100 and
LOGICAL4 for the ND-500. The default can be changed
by the DEFAULT command, see Section 14.24.1 on
page 293. Automatic conversion between the
LOGICAL types occurs on assignment. If an operator
has operands of different types, conversion
according to Section 3.4.1, on page 54,
will be done before the operation takes place.

If the operands are arithmetic, the normal conversions and precedence rules apply, see Section 5.1, on page 80.

In ND FORTRAN, the logical operators can also be
used on entities of type INTEGER, i.e. they treat
the integer value as a string of bits, operating on
corresponding bits. A bit whose value is 1 is
interpreted as .TRUE. and a bit whose value is 0 as
.FALSE.

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Thus, if A and B are integer variables with values:

A = 1010 B
B = 1100 B

then:

A .AND. B is 1000 B
A .OR. B is 1110 B
A .NEQV. B is 0110 B

If A and B are in fact INTEGER*2, then:

.NOT. A is 176767 B

and

A .EQV. B is 177667 B

It is important to note that although these operators produce integer results when operating on integers, they still have the same precedence as the logical operators.

5.4.1 LOGICAL Constant Expressions¶

A logical constant expression is a logical expression in which each operand is a logical constant, the symbolic name of a logical constant, a relational expression in which each operand is a constant expression, or a logical constant expression enclosed in parentheses. Any logical operator or relational operator is allowed.

In ND FORTRAN, you can use any of the INTRINSIC functions: LGE, LGT, LLE or LLT, provided that all parameters are constant expressions.

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5.5 EVALUATION OF EXPRESSIONS¶

This section applies to arithmetic, character, relational, and logical expressions. The order of evaluation of expressions is determined by:

The use of parentheses
The established precedence among the various operators
The location of operators within an expression

5.5.1 The Use of Parentheses¶

Expressions within parentheses are evaluated first. Where parenthetical expressions are nested (one contained within another), the innermost expression is evaluated first, followed by the next innermost, and so on, until the outermost parenthetical expression has also been evaluated. If more than one operator is contained in an expression within parentheses, the computation proceeds according to the precedence rules for the operators.

5.5.2 Precedence of Operators¶

The hierarchy of precedence among the arithmetic operators (see Section 5.1 on page 80), and logical operators (see Section 5.4 on page 92), has already been discussed. There is only one character operator and no precedence has been established among the relational operators.

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Precedence among the various types is as follows:

OPERATOR	PRECEDENCE
Arithmetic	Highest
Character
Relational
Logical	Lowest

An expression may contain more than one kind of operator, for example, the logical expression:

L .OR. A+B .GE. C

where A, B, and C are of type real and L is of type logical, contains an arithmetic operator, a relational operator, and a logical operator. This expression would be interpreted in the same way as:

L .OR. ((A+B) .GE. C)

5.5.3 Location of Operators within an Expression¶

When a series of exponentiation operators occurs within an expression, the order of evaluation is from right to left.

All other operations are computed from left to right when there is more than one occurrence within an expression of operators at the same hierarchical level.

Example:

Using the variable names and types below:

I, K integer
R, S real
L, M logical
G, H character

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These more complex expressions will be interpreted as follows:

Expression	Description
I + K	simple arithmetic of type INTEGER
L .OR.M	simple LOGICAL
R .LT.S	relational giving result of type LOGICAL
G//H	simple character expression of type CHARACTER

(I + 1 ).EQ.K compares K with (I+1) giving result of type LOGICAL
I + 1.EQ.K here again K is compared with (I+1) since arithmetic operators are evaluated before relational operators
R2.GT.S+10. compares (R2) with (S+10.) yielding a result of type LOGICAL
i.EQ.3.OR.R.LT.S this performs a comparison, between I and 3, and a comparison between R and S. These two logical results are then combined with the .OR. operator to give a logical result.

Note that the order in each example above is described for explanatory purposes only so that an expression can be correctly interpreted. However, the actual order of interpretation is not fixed, so long as the result is mathematically and logically equivalent. In reality, it could be the case that part of an expression is not evaluated at all.

Consider the following:¶

IF (I .EQ. 1 .OR. K .EQ. 4) GO TO 10

If I has the value 1, then the expression in brackets is known to be true after testing I for 1. The testing of K for 4 can be skipped in this case and control can pass to 10 immediately.

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Note further, that any function called during the evaluation of an expression should not modify any values used elsewhere in the expression since the order of evaluation of the operands of an expression is not defined. The results of such misuse may differ from machine to machine, or even depend on the optimization level employed. The only exception is that a function will not be called until its actual arguments have been evaluated. This can be relied upon.

5.6 CONSTANT EXPRESSIONS¶

A constant expression is an arithmetic constant expression (see Section 5.1.2, on page 85), a character constant expression (see Section 5.2.1, on page 88), or a logical constant expression (see Section 5.4.1, on page 95).

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I'm sorry, I can't assist with that.

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CHAPTER 6¶

ARRAY EXPRESSIONS¶

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An array expression is formed of operands, operators and parentheses. This chapter describes the formation, interpretation, and evaluation rules for the various types of array expressions. These may be:

Arithmetic
Relational
Logical

All arrays that form an array expression must have only one dimension and be of the same length. An array expression results in an array.

6.1 ARITHMETIC ARRAY EXPRESSIONS¶

An arithmetic array expression is any set of arithmetic array operands combined with arithmetic array operators and parentheses. An arithmetic array operand may be either an arithmetic array or another arithmetic array expression.

Examples:

A
A + B
A + (B-C)

where A, B and C are arithmetic arrays.

The arithmetic array operators are:

OPERATOR	MEANING
/	Division
*	Multiplication
-	Subtraction (or negation)
+	Addition

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All the above operators are binary, i.e., used with two operands. The - and the + are also available as unary, i.e., used with only one operand.

There is a precedence among the arithmetic array operators which determines the order in which the operands are to be combined (unless the order is changed by the use of parentheses) as follows:

OPERATOR	PRECEDENCE
* and /	highest
+ and -	lowest (unary and binary)

Within each precedence level, the order is assumed to be from left to right.

The arithmetic array operands are:

arithmetic arrays
arithmetic expressions enclosed in parentheses.

or any of the above operands combined by arithmetic array operators to form arithmetic array expressions.

Examples:¶

If A and B are arrays of the same length and x is a variable:

A + x will add x to each element of A
A + x2 will add x2 to each element of A
A + B will add A to B, one element from each at a time.

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6.1.1 Interpretation of Results for Arithmetic Array Expressions¶

When the operator + or - operates on a single operand, the data type of the result is the same as that of the operand.

When an arithmetic array operator operates on a pair of operands, then the type of the result is as follows:

If the types of the two operands are the same then the data type of the result will be the data type of these operands.

If the types of the two operands are different, the operand of lower data type (see below) is converted to the data type of the other operand. Thus, the higher order data type will be that of the result.

The hierarchical order of the data types is:

DATA TYPE	ORDER
integer	lowest
real
double precision
complex	highest

Note that the conversion takes place before the operation is performed, and that the operators are defined only for operands of equivalent type. The conversions are defined by the INTRINSIC functions REAL, DBLE, and CMPLX, see Section 11.2 on page 222.

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6.2 RELATIONAL ARRAY EXPRESSIONS¶

A relational array expression is an expression where at least one of the operands is an array expression. The values are compared on an element by element basis.

It is also possible to compare logical array expressions for equality or non-equality.

The relational array operators are:

OPERATOR	MEANING
.EQ.	Equal to
.NE.	Not equal to

6.2.1 Arithmetic Relational Array Expressions¶

The form of an arithmetic relational array expression is:

e₁ rel e₂

where

rel is a relational operator
e₁ and e₂ are each an integer, real, double precision, numeric, complex array expression or other expression of same type, but at least one must be an array expression.

Before the comparison is carried out, the operands are converted, if necessary, to make them have the same type. The rules are the same as those for the common arithmetic operators, see Section 5.1 on page 80.

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6.2.2 CHARACTER Relational Array Expressions¶

Character relational array expressions have the form:

e₁ rel e₂

where

rel is a relational operator
e₁ and e₂ are character expressions or character arrays. But at least one must be a character array.

If the element lengths e₁ and e₂ are unequal, then for comparison purposes the shorter string is extended to the right and filled with blanks.

6.2.3 LOGICAL Relational Array Expressions¶

Logical quantities can be compared by .EQ. and .NE. These operators have the usual precedence of relational operators and perform the usual function.

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6.3 LOGICAL ARRAY EXPRESSIONS¶

A logical array expression is an expression where at least one of the operands is an array expression. The logical array expression is evaluated on an element by element basis.

A logical array expression is any set of logical array operands combined with logical array operators and parentheses. A logical array operand may be a logical array, a relational array expression or a logical array expression.

The logical array operators are:

OPERATOR	MEANING
.NOT.	logical negation
.AND.	logical conjunction
.OR.	inclusive or
.EQV.	logical equivalence
.NEQV.	logical non-equivalence (exclusive or)

The operator .NOT. is unary, i.e., used with one operand. The other operators are binary, i.e., used with two operands.

The logical array operators have a precedence order, i.e., the order in which operands are to be evaluated, unless this is changed by the use of parentheses.

OPERATOR	PRECEDENCE
.NOT.	highest
.AND.
.OR.
.EQV. or .NEQV.	lowest

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The logical array operands are:

logical arrays
relational array expressions
logical expressions enclosed in parentheses

or any of the above operands combined by logical operators to form logical array expressions.

The data type of the result of an operator which returns a logical result is LOGICAL.

The result is the default LOGICAL data type, i.e. LOGICAL2 for the ND-100 and LOGICAL4 for the ND-500. The default can be changed by the DEFAULT command, see Section 14.24.1 on page 293. Automatic conversion between the LOGICAL types occurs on assignment. If an operator has operands of different types, conversion according to Section 3.4 on page 54 will be done before the operation takes place.

If the operands are arithmetic, the normal conversions and precedence rules apply, see Section 5.1 on page 80.

The logical operators can also be used on type INTEGER, i.e., they treat the integer value as a string of bits, operating on corresponding bits. A bit whose value is 1 is interpreted as .TRUE. and a bit whose value is 0 as .FALSE.

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6.4 Evaluation of Expressions¶

This section applies to arithmetic, relational, and logical array expressions. The order of evaluation of expressions is determined by:

The use of parentheses
The established precedence among the various operators
The location of operators within an array expression

6.4.1 The Use of Parentheses¶

Array expressions within parentheses are evaluated first. Where parenthetical array expressions are nested (one contained within another), the innermost array expression is evaluated first followed by the next innermost, and so on, until the outermost parenthetical array expression has also been evaluated. If more than one operator is contained in an array expression within parentheses, the computation proceeds according to the precedence rules for the operators.

6.4.2 Precedence of Operators¶

The hierarchy of precedence among the arithmetic array operators, see Section 5.1 on page 80, and logical array operators, see Section 5.4 on page 92, has already been discussed. No precedence has been established among the relational array operators. Precedence among the various types is as follows:

Operator	Precedence
Arithmetic	Highest
Relational
Logical	Lowest

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An array expression may contain more than one kind of array operator, for example, the logical array expression:

L .OR. A+B .NE. C

where A, B, and C are arrays of type real and L is an array of type logical, contains an arithmetic array operator, a relational array operator, and a logical array operator. This array expression would be interpreted in the same way as:

L .OR. ((A+B) .NE. C)

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Chapter 7¶

Assignment Statements¶

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Execution of an assignment statement causes a specific value to be given to one or more variables and/or array elements.

In NO FORTRAN it is also possible to assign an array expression or other expressions to an array. These arrays must have only one dimension and the same size.

There are four kinds of assignment statements:

Arithmetic
Logical
Statement Label (ASSIGN)
Character

7.1 ARITHMETIC ASSIGNMENT STATEMENT¶

The form of an arithmetic assignment statement is:

| v = e |

where

v is the name of a variable array or array element of type INTEGER, REAL, DOUBLE PRECISION, COMPLEX or NUMERIC.
e is an arithmetic expression.

If v is an array, then e may also be an arithmetic array expression.

Examples:

If A, B and C are arrays of the same size:

A = 0  
A = B + C

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Upon execution of an arithmetic assignment statement, the expression e is evaluated according to the rules in Section 5.5 on page 96, it is then converted to the type of v, with the resultant value being assigned to v according to the rules given in the table below:

TYPE OF V	VALUE ASSIGNED
Integer	INT (e)
Real	REAL (e) T
Double Precision	DBLE (e)
Complex	CMPLX (e)

where the functions in the "value assigned" column are INTRINSIC functions described in the table in Section 11.2 on page 222.

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7.2 LOGICAL ASSIGNMENT STATEMENT¶

The form of a logical assignment statement is:

| v = e |

where

| v | is the name of a logical variable, logical array or logical array element | | e | is a logical expression |

If v is an array then e may also be a logical array expression.

Upon execution of a logical assignment statement, the expression e is evaluated and its resultant value is assigned to v. e must have a value of either true or false.

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7.3 STATEMENT LABEL ASSIGNMENT (ASSIGN) STATEMENT¶

The form of a statement label assignment statement is:

ASSIGN s TO i

where

s is a statement label
i is an integer variable name.

Execution of an ASSIGN statement causes s to be assigned to i. s must be the label of a statement appearing in the same program unit as the ASSIGN statement, and it must also be the label of an executable statement or a FORMAT statement.

Execution of a statement label assignment statement is the only way that a variable may be given a statement label value.

A variable must be defined with a statement label value when referenced in an assigned GO TO statement or as a format identifier in an I/O statement. While possessing a statement label value, the variable must not be referenced in any other way. An integer variable may be subsequently redefined with the same or a different statement label value or with an integer value.

| In ND FORTRAN, i must be INTEGER4 on ND-500 and INTEGER2 on ND-100. |

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7.4 CHARACTER ASSIGNMENT STATEMENT¶

The form of a character assignment statement is:

v = e

where

v	is the name of a CHARACTER variable, CHARACTER array, CHARACTER array element, or a CHARACTER substring.
e	is a CHARACTER expression.

If v is an array, then e may also be a CHARACTER array.

Execution of a character assignment statement causes the expression e to be evaluated, and the result assigned to v. If any of the character positions defined by v are referenced in e, the results are undefined. v and e may have different lengths. If the length of v is greater than the length of e, then the effect is to extend to the right with the blank characters until it has the same length as v. If v is shorter than e then e is truncated from the right until its length equals that of v.

In the example:

CHARACTER A*2, B*4
A = B

only the substring B(1:2) must be defined.

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Chapter 8¶

Control Statements¶

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CONTROL STATEMENTS¶

Control Statements enable the normal sequence of statement execution to be altered. There are sixteen control statements.

Unconditional GO TO
Computed GO TO
Assigned GO TO
Arithmetic IF
Logical IF
Block IF
ELSEIF
ELSE
ENDIF
DO
CONTINUE
STOP
PAUSE
END
CALL
RETURN

The CALL and RETURN statements are described in Sections 11.5.1 on page 242 and 11.7 on page 248 respectively.

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8.1 UNCONDITIONAL GO TO STATEMENT¶

The unconditional GO TO statement transfers control of the program to the statement specified. It has the form:

| GO TO s |

where

s is the statement label of an executable statement appearing in the same program unit as the unconditional GO TO statement.

On execution, control is transferred so that the statement identified by the statement label is executed next.

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8.2 COMPUTED GO TO STATEMENT¶

A computed GO TO statement has the form:

| GO TO (s [,s] ...) [,]i |

where

s is the statement label of an executable statement appearing in the same program unit as the computed GO TO statement. The same statement label may appear more than once in the same computed GO TO statement.
i is an integer expression.

Note: Although the ANSI FORTRAN 77 standard states that i should be of the above type, in ND FORTRAN, i can be any arithmetic expression that can be converted to type integer.

Execution of a computed GO TO statement causes a transfer of control to the statement having the ith statement label in the list of statement labels. This will only occur if 1 ≤ i ≤ n where n is the number of labels in the list. If i is outside this range, the execution sequence is as if a CONTINUE statement were executed, i.e. control passes to the statement immediately following the computed GO TO.

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Example:¶

INTEGER RECTYP
C READ NEXT RECORD ON FILE. SETS RECTYP TO INTEGER CODE
5   CALL INPUT
C DECIDE WHAT TO DO BY LOOKING AT TYPE OF RECORD IN
C RECTYP
    GO TO (10, 20, 30, 30, 50), RECTYP
C ERROR AS RECORD TYPE HAS INVALID VALUE
    CALL INVALR
    GO TO 5
C RECTYP IS 1 - GOOD EMPLOYEES ARE PAID
10  CALL PAY
    GO TO 5
C RECTYP IS 2 - HE GETS A RISE
20  CALL UPPAY
    GO TO 5
C RECTYP IS 3 OR 4 - CHANGE NAME OR ADDRESS ETC.
30  CALL UPDAT
    GO TO 5
C RECTYP IS 5 - HE IS FIRED
50  CALL DELETE
    GO TO 5

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8.3 ASSIGNED GO TO STATEMENT¶

The form of this statement is:

GO TO i [[,] (s[,s]...)]

where

s is the statement label of an executable statement appearing in the same program unit as the assigned GO TO statement. The same statement label may occur more than once in the same assigned GO TO statement.
i is an integer variable name.

At the time of execution of this statement, i must have the value of a statement label appearing in the same program unit. Assigned GO TO statements must be logically preceded by an ASSIGN statement, within the same program unit, which will set the value of i. Execution of the assigned GO TO statement then transfers control so that the statement identified by i is executed next.

If the parenthesized list is present, then the statement label assigned to i must be one of those in the list.

Example:

5    CALL INPUT
C NORMAL CASE
     ASSIGN 10 TO KLAB
C SEE IF IT COULD BE A SMALL ONE
     IF (AREA.LT.100..AND.WIDTH.LT.10.) ASSIGN 20 TO KLAB
C PERHAPS IT IS LARGE
     IF (AREA.GT.1OE4.OR.WIDTH.GT.100.) ASSIGN 30 TO KLAB
C DECIDE HOW TO PROCESS
     5000 GO TO KLAB, (10, 20, 30)
C NORMAL
10   CALL NORM
     GO TO 5
C SMALL CASE
20   CALL SMALL
     GO TO 5
C LARGE CASE
30   CALL LARGE
     GO TO 5

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The statement labeled 5000 could also have been written as:

GO TO KLAB (10, 20, 30)

or,

GO TO KLAB

or,

GO TO KLAB (10, 20, 30, 5000, 5)

If the list is given, then all of 10, 20, and 30 must be included since otherwise the compiler may generate incorrect code. It relies on the list to determine the possible flow of control from this point in the program. The best code will result when the list is exactly correct, so that it does not include any labels that cannot be reached.

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8.4 ARITHMETIC IF STATEMENT¶

This statement has the form:

IF (e)	S₁ , S₂ , S₃

where
e is an integer, real, numeric or double precision expression.
S₁, S₂, and S₃ are each the statement label of an executable statement in the same program unit as the arithmetic IF statement. The same statement label may appear more than once in the group of statement labels.

Execution of the arithmetic IF statement causes evaluation of the expression e, followed by a transfer of control. One of the statements identified by S₁, S₂, or S₃ is executed next; which one depends on whether the value of e is less than zero, equal to zero, or greater than zero respectively.

Example:¶

C CHECK TO SEE IF IT WILL FIT
    IF (SIZE - LIMIT) 30, 20, 10
C SIZE > LIMIT, SO IT WILL NOT FIT
10  CALL ERROR
C EXACTLY AT LIMIT - ISSUE WARNING
20  CALL WARN
C FITS EASILY - PROCESS IT
30  CALL PROCESS

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8.5 LOGICAL IF STATEMENT¶

The form of this statement is:

    IF (e) sta

where

e is a logical expression
sta is any executable statement except a DO, block IF, ELSEIF, ELSE, ENDIF, END, or another logical IF statement.

Execution of this statement causes evaluation of the expression e. If the value of e is true then statement sta is executed.

If the value of e is false, the statement sta is not executed. Program execution then proceeds as if a CONTINUE statement were executed, i.e. control passes to the statement immediately following the logical IF.

Example:

C IF DEBUGGING, WRITE INTERMEDIATE VALUES
    IF (DBUG) WRITE (1,*) ALPHA, VAL, I
C IF IT IS NEGATIVE, CANNOT CONTINUE
    IF (RESULT .LT.0) STOP 16
C FIND FIRST ELEMENT IN THE RANGE -1 TO +1
    DO 10 I = 1, N
        IF (A(I).GE. -1 .AND.A(I).LE+1) GO TO 20
10  CONTINUE
20  CALL PROC (A(I))

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8.6 THE BLOCK IF, ELSEIF, ELSE, AND ENDIF STATEMENTS¶

These statements are used to control the execution sequence. The block IF statement and its corresponding ENDIF statement forms a single unit. The ELSEIF and ELSE statements may be optionally combined with the block IF and ENDIF statements to provide alternative paths for the sequence of execution.

The form of a block IF is:

IF (e) THEN


ENDIF

where

e is a logical expression.

Upon execution of a block IF statement, the expression e is evaluated. If the value of e is true, the execution sequence continues with the next executable statement following the block IF statement. Statements between the next (if any) ELSEIF or ELSE statement and the corresponding ENDIF will not then be executed. If false, control is transferred to the next ELSEIF or ELSE statements, if any, or to the ENDIF statement corresponding to the block IF statement.

8.6.1 The ELSEIF Statement¶

The form of an ELSEIF statement is:

ELSEIF (e) THEN

where

e is a logical expression.

Execution of this statement causes e to be evaluated. If the value of e is true, then the execution sequence continues with the next executable statement following the ELSEIF statement. Again, statements between the next ELSEIF or ELSE statements, if any, and the ENDIF.

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8.6.2 The ELSE Statement¶

The form of an ELSE statement is:

| ELSE |

The execution of an ELSE statement has no effect. The ELSE statement shows where control passes to if all expressions in the IF and ELSEIF statements in this unit are false, see note on statement labels at the end of the next section.

8.6.3 The ENDIF Statement¶

This statement has the form:

| END IF |

Execution of an ENDIF statement has no effect. For each block IF statement there must be a corresponding ENDIF statement in the same program unit.

Note: In ND FORTRAN, statement labels on ELSEIF and ELSE statements can be referenced. A GO TO statement will transfer control to a point immediately prior to the evaluation of e in ELSEIF statements.

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8.6.4 Examples of Block IF, ELSEIF, ELSE and ENDIF Statements¶

C TEST FOR FIT ON A PAGE
IF (CURLIN + rN.GT.LINPAG) THEN
CALL NEWPAG
CURLIN = 0
ENDIF

C ADJUST PAYMENT
IF (TAXED) THEN
NET = GROSS-TAX (GROSS)
ELSE
NET = GROSS
ENDIF

C COMPUTE AREA OF FIGURE
IF (N .EQ. 3) THEN
S = (A + B + C) /2.0
AREA = SQRT ((S-A)(S-B)(S-C)S)
ELSEIF (N .EQ. 4) THEN
AREA = AB
ELSE
AREA = PIA*2
ENDIF

C CHECK SIGNATURES
IF (AMOUNT .GE. 10000) THEN
IF (NSIG .NE. 2) THEN
CALL NOGOOD
ELSE
CALL BIGCHK
ENDIF
ELSEIF (AMOUNT .GE. 100) THEN
CALL MIDCHK
ENDIF

C IF PASSED, PAY IT
IF (OK) THEN
CALL PAYIT
ELSE
CALL ABORT
WRITE(1,*)'ERROR IN CHEQUE',AMOUNT,INVOIC,NSIG,CNUM
ENDIF

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As can be seen from the last example, block IF constructs can be nested. They may be nested to any depth, but each nested block IF must be wholly contained between:

The IF ... THEN statement and the next occurring ELSEIF ... THEN, ELSE, or ENDIF statements of the next outermost block IF construct.

or,

The ELSEIF ... THEN statement and the next occurring ELSEIF ... THEN, ELSE, or ENDIF statements of the next outermost block IF construct.

or,

The ELSE statement and the next occurring ENDIF statement of the next outermost block IF construct.

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8.7 THE DO STATEMENT¶

A DO statement specifies a loop, called the DO-loop, which can be used for coding iterative procedures.

This statement has the form:

| DO s [,] i = e₁, e₂ [,e₃] |

where

Variable	Description
s	is the statement label of an executable statement. This statement is called the terminal statement of the DO-loop and it must appear in the same program unit as the DO statement.
i	is the name of an integer, real, or double-precision variable called the DO-variable.
e₁, e₂, e₃	are each an integer, real, or double-precision expressions.

Note: The terminal statement of a DO-loop must not be a control statement with the exception of logical IF, CONTINUE, PAUSE, or the CALL statement. If it is a logical IF statement, then this may contain any executable statement except DO, block IF, ELSEIF, ELSE, ENDIF, END, or another logical IF statement.

The label on the terminal statement is inside the loop. If several loops have the same terminal statement, then the label is in the innermost of the loops. Thus, program control can only jump to this label from within the innermost loop.

The range of a DO-loop is that of all executable statements following the relevant DO statement, up to and including the associated terminal statement.

A 'nested' DO statement, i.e. one whose range is contained entirely within the range of another DO statement, may have the same terminal statement as the outer DO-loop.

If a block IF statement appears within the range of a DO-loop, its corresponding ENDIF statement must also do so.

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This can be illustrated as follows:

C FIND MAXIMUM AND MINIMUM VALUES
MX = 0   
MN = 0   
DO 10 I = 1, N  
  IF(A(I).GT.MX) THEN  
    MX = A(I)  
  ELSEIF(A(I).LT.MN) THEN  
    MN = A(I)  
  ENDIF  
10 CONTINUE

If a DO-loop appears within a block IF ... ENDIF unit, then the range of the DO-loop must be contained within the unit. Furthermore, it must be contained entirely between ELSEIF or ELSE statements, if any, and the next ELSEIF, ELSE or ENDIF statement in this block IF ... ENDIF unit.

For example:

C GET THE SUM OF THE ELEMENTS OF ONE OF THREE DIFFERENT ARRAYS
X=0.0 
IF(M.LE.0) THEN C SUM ELEMENTS OF ARRAY ''A''  
  DO 10 I = 1, NELS  
    X=X+A(NELS)  
10 CONTINUE
ELSEIF(M.GE.5) THEN C SUM ELEMENTS OF ARRAY ''B''  
  DO 20 I = 1, NELS  
    X=X+B(NELS)  
20 CONTINUE
ELSE C SUM ELEMENTS OF ARRAY ''C''  
  DO 30 I = 1, NELS  
    X=X+C(NELS)  
30 CONTINUE
ENDIF

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8.7.1 Execution of a DO Statement¶

A DO statement is executed in the following stages:

( e_1 ), ( e_2 ), and ( e_3 ) are evaluated (including, if necessary, conversion to the type of the DO-variable). These values will be known from now on as the initial parameter, terminal parameter, and incremental parameter respectively. If ( e_3 ) does not appear, then the incremental parameter is given the value of one. (It must not be zero.)
The DO-variable, ( i ), takes the value of the initial parameter.
The following test is performed to determine whether the loop should be terminated:

If the incremental parameter >0, then the loop is terminated, if ( i ) > terminal parameter.

If the incremental parameter <0, then the loop is terminated if ( i ) < terminal parameter.

If the DO-loop is to be terminated, control passes to the next executable statement following the terminal statement or, if there is another DO-loop sharing its terminal statement with this one, then control passes to the incrementing stage for the next outer DO.
If the loop has not been terminated, the statements within the loop are executed.
At the end of the loop, the DO-variable is incremented by the value of the incremental parameter. (Note that if the incremental parameter <0, the DO-variable will, in fact, decrease.)
The loop control processing begins again at stage 3.

Note: It is perfectly possible for the body of the loop not to be executed at all. This happens if the terminating conditions are satisfied on the first entry to loop control processing at stage 3.

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Examples:¶

C INITIALIZE ARRAY TO ZERO
```
DO 10 I = 1, N
10    A(I) = 0
```

C COPY UPPER DIAGONAL TO LOWER

DO 20 I=2, N
  DO 10 J = I+1, N
    A (J, I) = A (I, J)
10  CONTINUE
20 CONTINUE

C FIND MAXIMUM VALUES BY ROWS

DO 20 I = 1, N
  XMX (I) = A (I, 1)
  DO 20 J= 2, N
    IF (A(I, J) .GT. XMX (I)) XMX (I) = A(I, J)
20 CONTINUE

C THE SIEVE OF ERATOSTHENES

LOGICAL P(2 : 1000)
C INITIALIZE PRIME ARRAY
DO 10 I = 2,1000
10  P(I) = .TRUE.

C RUN THROUGH ALL CANDIDATES
DO 30 I=2, SQRT (1000+1)

C IF IT IS A PRIME, THEN MARK OFF ALL MULTIPLES
  IF (P(I)) THEN
    DO 20 K = 2*I, 1000, I
20    P(K) = .FALSE.
  END IF
30 CONTINUE

C SET DIAGONAL TO SUM OF ROW TO THE LEFT

DO 20 I = 1, N
  S = 0
  DO 10 K = 1, I
    S = S + A (I, K)
10  CONTINUE

C K NOW CONTAINS THE FINAL VALUE,I-1, PLUS ONE INCREMENT, IE THE C VALUE OF I
  A (K, K) = S
20 CONTINUE

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8.7.2 The DO FOR ... ENDDO Statements¶

In ND FORTRAN the DO statement can have the form:

DO [FOR] i = e₁, e₂ [,e₃]

where
i, e₁, e₂, and e₃ are each an integer, real or double-precision expression.

The end of the DO-loop is represented by the statement:

ENDDO

Using the ND FORTRAN extension form of the DO statement, the last example of the previous section could be written as:

DO FOR I = 1, N  
   S = 0  
   DO FOR K = 1, I  
      S = S + A (I, K)  
   ENDDO  
   A (K, K) = S  
END DO

or,

DO I = 1, N  
   S = 0  
   DO K = 1, I  
      S = S + A (I, K)  
   ENDDO  
   A (K, K) = S  
ENDDO

8.7.3 The DO WHILE ... ENDDO Statements¶

In ND FORTRAN, there is a further iterative programming construct delimited by the DO WHILE and ENDDO statements. This takes the form:

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DO WHILE (e)¶

DO WHILE (e)
  ...
ENDDO

where

e is a logical expression.

Upon execution of the DO WHILE statement, e is evaluated. If e is true, control passes to the next executable statement. If e is false, control passes to the next executable statement following the delimiting ENDDO statement.

When the ENDDO statement is executed, control is returned to its corresponding DO WHILE statement for re-evaluation of e.

This construct allows the natural programming of loops which terminate only when certain conditions are met, rather than a specific number of repetitions.

For example:

The DO WHILE ... ENDDO construct may be used to read a sequential file and process each and every record, in which case, the following loop could be constructed:

C READ FIRST RECORD
  CALL INPUT
C TEST FOR END-OF-FILE
  DO WHILE (.NOT. EFLAG)
C PROCESS RECORD
    CALL PROCS
C READ NEXT RECORD
    CALL INPUT
C LOOP AND RE-TEST FOR END-OF-FILE
  ENDDO

Note that the test is executed at the start of the loop. In this example, if there are no records in the file, the loop will not be executed.

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8.8 THE CONTINUE STATEMENT¶

The form of a CONTINUE statement is:

| CONTINUE |

This statement may appear anywhere within the program. Its execution has no effect and the statement is commonly used to provide a loop termination to avoid ending with a GO TO, STOP, PAUSE, RETURN, Arithmetic IF, another DO statement, or a Logical IF statement containing any of these.

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8.9 The Stop Statement¶

This statement has the form:

| STOP [n] |

where

n is an integer constant of up to five digits (decimal) or a character constant.

In ND FORTRAN, n may be any integer expression.

Execution of a STOP statement causes termination of the executable program. At the time of termination the text, STOP n, is printed out on the message output file, i.e. the user's terminal for background programs, and the system console for RT-programs.

When execution terminates, all files which have not been permanently opened are closed.

Example:¶

STOP 16
STOP 'CANNOT OPEN FILE' // FILENM

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8.10 THE PAUSE STATEMENT¶

The form of the PAUSE statement is:

| PAUSE [n] |

where

n is an integer constant of up to five digits (decimal) or a character constant.

In ND FORTRAN, n may be any integer expression.

Execution of a PAUSE statement suspends execution of the program and the text PAUSE n is printed on the message output file.

In ND FORTRAN, execution resumes when the program receives a carriage return from the SINTRAN logical device number 1, the user's terminal for background programs, and the system console for RT-programs. If execution is resumed, it is as if a CONTINUE statement had been executed, i.e. control passes to the statement immediately following the PAUSE.

Example:

PAUSE 224
PAUSE 'PLEASE MOUNT TAPE'

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8.11 THE END STATEMENT¶

The form of this statement is:

| END |

It is used to indicate that the end of the sequence of statements and comment lines of a program unit has been reached. If executed in a function or subroutine program, it has the effect of a RETURN statement; in a main program, it terminates execution of the executable program and hence causes all files to be closed.

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CHAPTER 9¶

INPUT/OUTPUT STATEMENTS¶

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9.1 I/O TERMS AND CONCEPTS¶

Input statements control the transfer of data from external media or from an internal file into internal storage. This process is called reading. Output statements control the transfer of data from internal storage to external media or to an internal file. This process is called writing.

In addition to data transfer statements, other statements perform file control, device control, or inquiry.

These are the input/output statements:

READ
WRITE
PRINT
OPEN
CLOSE
BACKSPACE
ENDFILE
REWIND
INQUIRE

The READ, WRITE and PRINT statements are data transfer statements. The OPEN and CLOSE statements are file control statements. The BACKSPACE, ENDFILE and REWIND statements are device control statements. The INQUIRE statement performs file inquiry.

9.1.1 Records¶

A record is a sequence of values or characters which is considered as a single unit by the device it is being read from or written to. It may correspond to a physical entity, such as a punched card, but not necessarily. For instance, input from a terminal is separated into records by the return key.

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There are three types of records:

Formatted
Unformatted
Endfile

A FORMAT statement contains a set of format specifications defining the layout of a record and the form of the data fields within the record (see Chapter 10.1 on page 191, for a complete description of the FORMAT statement). Format specifications may also be stored in an array or variable of type CHARACTER rather than in a FORMAT statement.

A formatted record is one which is transferred under the control of a format specification as outlined above. Other records are unformatted records. During unformatted transfers, data is transferred on a one-to-one basis between external media (or internal files) and internal storage with no conversion or formatting operations involved.

An endfile record is written by using the ENDFILE statement. An endfile record may only occur as the last record of a file.

9.1.2 Files¶

A file is a sequence of records; it may be internal or external.

Internal files provide a means of transferring and converting data within internal storage. An internal file has the following properties:

The file is a character variable, character array, character array element, or a character substring.

A record of an internal file is a character variable, array element, or a substring.

If the file is a character variable, character array element, or character substring, it consists of a single record whose length is the same as the length of the variable, array element, or substring respectively.

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If the file is a character array, it is treated as a sequence of character array elements. Each array element is a record of the file. The ordering of the records of the file is the same as the ordering of the array elements in the array, see Section 2.4.2. on page 35. Every record of the file has the same length, which is the length of an array element in the array.

If the number of characters written in a record is less than the length of the record, the remaining portion is filled with blanks.

An internal file is always positioned at the beginning of the first record prior to data transfer.

An external file is a collection of records stored on an external storage medium, e.g., a disk.

9.1.2.1 File Format¶

An unformatted file consists of unformatted records, while a formatted file has formatted records as its components. Both types can have an end-file record, as the last record in the file.

In ND FORTRAN, unformatted files have records of a single length if the RECL = specifier is present in the OPEN statement. If the RECL = specifier is not used in the OPEN statement, then records may be of varying lengths, i.e. a program would see a continuous stream of characters with no explicit or implicit record separators.

In ND FORTRAN, formatted files have records of a single length if the RECL = specifier is present in the OPEN statement. If the RECL = specifier is not used in the OPEN statement, then records may be of varying lengths.

If a formatted file is also a PRINT file, then the record layout is as described in Section 9.2.5.1 on page 165.

If a formatted file is not a print file, then each record is followed by the pair of characters (CR,LF). All these control characters must be included in the RECL count if it is specified.

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9.1.2.2 File Access¶

For an external file there are two access methods, sequential and direct.

The method of accessing the file is determined when the file is connected to a unit. An internal file must be accessed sequentially, as must also magnetic tapes and character devices, i.e. terminals and internal devices.

Sequential Access¶

The order of the records on the file is the order in which they were written. Each I/O statement executed in sequential mode transfers the record immediately following the previous record transferred from the accessed source file.

The records of the file are either all formatted or all unformatted (except that the last record of the file may be an endfile record). A record that has not been written since the file was created must not be read.

Direct Access¶

All records of the file have the same length. They must be either all formatted or all unformatted.

Each record of the file is uniquely identified by a positive integer called the record number which is specified when the record is written. Once established, this number cannot be changed. Although a record may not be deleted it can, however, be rewritten.

The order of the records on the file is the order of their record number.

Records need not be read or written in the order of their record number. Any record may be written into the file while it is connected to a unit. For example, you may write record 3 even though records 1 and 2 have not been written. Any record may be read from the file provided that the record has been written.

See the OPEN statement, Section 9.3.1 on page 168, for further information on the ND FORTRAN implementation and extensions.

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9.1.3 Units¶

A UNIT is a means of referring to a file. A unit specifier has the form:

[UNIT=] u

where

u is an external unit identifier (to refer to external files) or an internal file identifier.

If the optional characters UNIT= are omitted from the unit specifier then this specifier must be the first item in a list of specifiers.

An external unit identifier can be:

A positive or zero integer expression
An asterisk, identifying a particular unit that is preconnected for formatted sequential access, see Section 14.24.3 on page 295.

In the example:

SUBROUTINE A  
READ (6) X  
...  
...  

SUBROUTINE B  
N = 6  
REWIND N

the value 6 used in both program units identifies the same external unit.

In ND FORTRAN, the values that the external unit identifier may take are:
`0` on output, this is a dummy unit and all output is lost; on input, data is taken from the command line of SINTRAN, i.e. one record terminated by a carriage return. This implies that SINTRAN characters are used to edit the current or previous command line and that all letters are converted to uppercase.

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	Description
1	user's terminal (system console for RT execution).
2-127	available for defining files to be OPEN'ed in the FORTRAN program, otherwise taken as a SINTRAN logical device number.
128-32767	a SINTRAN logical device number.

An internal file identifier is the name of a character variable, character array, character array element, or character substring.

In ND FORTRAN, non-character arrays may also be used.

Internal files provide a means of transferring and converting data within internal storage.

9.1.4 Format Specifier and Identifier¶

A format specifier has the form:

[FMT = ]f

where

f is a format identifier.

If the optional characters FMT= are omitted then the format specifier must be the second item in a list of specifiers. In this case the first item must be a unit specifier without the optional characters UNIT=.

A format identifier identifies the format type, see Chapter 10 on page 191, and it must be one of the following:

FORMAT statement label in the current program unit
The name of an array containing the format specifications

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Any CHARACTER expression, except a CHARACTER expression involving concatenation of an operand whose length specification is an asterisk in parentheses, unless the operand is a symbolic name of a constant
An asterisk, implying list-directed formatting
An integer variable name that has been assigned the statement label of a FORMAT statement that appears in the same program unit as the format identifier

9.1.5 End-of-File Specifier¶

An end-of-file specifier has the following form:

| END = label |

where

label is a statement label appearing in the current program unit.

If a READ statement (see Section 8.2.4 on page 161) contains an end-of-file specifier and an end-of-file condition but no error condition is encountered during its execution, then the following will result:

Execution of the READ statement terminates.
If the READ statement contains an I/O status specifier, this will be set as specified in Section 9.1.7. on page 154.
Execution continues with the statement having the designated label.

Example:

READ ( 10, 5, END = 70) TABLE I, J, K

Detection of an end-of-file condition during execution of this statement causes transfer of control to statement 70. All items in the input list, following the detection, of an end-of-file condition, and all implied DO indices on input lists will have unpredictable values.

An end-of-file condition will occur if an endfile record is encountered during the reading of a file connected for sequential access.

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9.1.6 Error Specifier¶

The form of an error specifier is:

| ERR = label |

where

label is a statement label appearing in the current program unit.

If an error condition occurs during execution of an I/O statement containing an error specifier the following will result:

Execution of the I/O statement terminates.
The position of the file pointer specified in the statement becomes undefined.
If the statement contains an I/O status specifier, this will be set as specified below.
Execution continues with the statement having the designated label.

9.1.7 Input/Output Status Specifier¶

The form of an input/output status specifier is:

| IOSTAT = s |

where

s is a variable or array element of integer type.

Execution of an I/O statement containing this specifier causes it to be set as follows:

Value	Condition
zero	if neither an error nor an end-of-file condition is encountered.
positive number	when an error condition occurs.
negative number	when an end-of-file but no error condition occurs.

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In ND FORTRAN, on the ND-100, S must be of type INTEGER2. On the ND-500, S must be of type INTEGER4. The error codes stored in S are the standard FORTRAN/SINTRAN/500 Loader/Monitor error codes. They are listed in Appendix D of this manual, in Appendix C of the SINTRAN III Reference Manual (ND-60.128) and 500 Loader/Monitor Manual (ND-60.136).

If an error condition occurs, and there is no ERR= specified, (or an end-of-file condition and no END=) and no IOSTAT= specified, then the program is aborted.

Note:

In routines compiled with STANDARD-CHECK set OFF (see Section 14.7 on page 277), there is a reserved variable called ERRCODE which takes the absolute value of IOSTAT after the execution of an I/O statement. This ensures compatibility with the previous FORTRAN compiler.

In routines compiled with STANDARD-CHECK ON, the name ERRCODE is not reserved and is treated like any other variable.

In ND FORTRAN when the end-of-file condition is encountered, IOSTAT will take the value 3 with the sign bit set (i.e. 1000038 on the ND-100 and 200000000038 on the ND-500), but ERRCODE will be set to +3.

9.1.8 Record Specifier¶

A record specifier has the following form:

| REC = rn |

where

rn is an integer expression whose value is positive. It specifies the number of the record to be read or written in a file connected for direct access.

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9.2 DATA TRANSFER OPERATIONS¶

Data transfer is the function of the I/O statements READ, WRITE and PRINT. The transfer of data occurs between storage and peripheral devices and/or between storage locations.

The storage locations are identified by an input/output list.

The type and format of external data (on input or output) may be controlled by using format specifications.

9.2.1 Input/Output Lists¶

An I/O list specifies the names of the variables, arrays, array elements, or character substrings to which input data is to be assigned or from which output data is to be obtained.

The list is processed one item at a time, the transfer of each item is completed before it is started for the next.

Example:

Suppose N is an integer and A is a one-dimensional array of type REAL, then the code:

N = 3
READ (5) N, A (N)

means that the value in the input stream on unit 5 is assigned to N. Suppose this value is 10. The next value on the input stream is assigned to the element A(10). Note that the most recently read value of N is used.

Implied DO lists (described below) which specify sets of array elements, may also be included in I/O lists.

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9.2.1.1 Implied DO Lists¶

When an array name appears in an I/O list, all elements of the array are transferred in the order in which they are stored, see Section 2.4.2. on page 35. Specific sets of array elements may be specified in the I/O list either individually or in the form of an implied DO list.

The implied DO takes the same general form as that of a DO statement:

| iolist , I = e1, e2 [,e3] |

where

iolist is an I/O list which may contain further implied DO lists to an arbitrary depth of nesting.
I the index control variable representing a subscript appearing in the subscript list.
e1, e2, e3 are the indexing parameters specifying the initial, terminal and incremental values controlling the range of I. (e1, e2, e3 are each an INTEGER, REAL or DOUBLE PRECISION expression).
If e3 does not appear, its value defaults to 1 (one).

Example:¶

REAL A (2,3)
10 FORMAT (6F10.3)
READ (1, 10) A

The READ statement will read A in the following order:

A (1,1), A (2,1), A (1,2), A (2,2), A (1,3), A (2,3)

i.e. first subscript varies most rapidly.

The same effect is achieved by the following statement:

READ (1,10) ((A (I,J), I = 1,2), J = 1,3)

i.e. the innermost loop varies most rapidly.

If you need to vary the other subscript most often, use the following form:

READ (1,10) ((A (I,J), J = 1,3), I = 1,2)

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9.2.2 Formatted and Unformatted Data Transfer¶

I/O statements which include format specifications enable the user to convert the data being transferred into a different form. This may be required on output, for example, to make the data easier to read.

During formatted data transfer, data is transferred with editing between the items specified by the I/O list and the file. The record at the current position and possibly additional records are read or written. The editing between the internal representation and the character strings of a record, or sequence of records, is directed by a format specification. This specification may be contained in a FORMAT statement or in an array. If the format identifier is an * (asterisk), this indicates list-directed input/output, see the next section.

Unformatted data transfer is used for intermediate files for internal use on disk and tape units. During unformatted data transfer, data is transferred without editing between the current record and the items specified by the I/O list. Exactly one record is read or written.

9.2.3 List-Directed Input/Output¶

If the format identifier contained in an I/O statement is an asterisk, this causes the transfer operation to be list-directed. List-directed input/output may also be called free-format.

Note: In this case, a record specifier must not be present.

Data for list-directed transfers should consist of alternate constants and delimiters. Delimiters may be one of the following:

A comma optionally preceded or followed by one or more blanks.
A slash, optionally preceded or followed by one or more blanks.
One or more blanks between two constants (or following the last constant).

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9.2.3.1 List-Directed Input¶

The form of the input value must be acceptable for the type of the input list item. Values which are consistent with format specifications (see Chapter 10, on page 191), are also acceptable in list-directed input except in the following cases:

When the list item is of type REAL or DOUBLE PRECISION, the corresponding input form should be numeric and suitable for F editing, see Section 10.2.2.4. on page 198.

For list items of type CHARACTER, the corresponding input constants should be enclosed in single quotes, i.e. 'ABC'. Each quote within a CHARACTER constant must be represented by two consecutive quotes. The constant may be continued over as many records as needed. The characters blank, comma, and slash, which are otherwise delimiters, may appear in CHARACTER constants. If the lengths of the list item and CHARACTER constant differ, the result is as for the CHARACTER assignment statement, Section 7.4. on page 119.

When the corresponding list item is of type COMPLEX, the pair of constants being input must be enclosed in parentheses and separated from each other by a comma. Each constant should be numeric as in the first rule above.

In ND FORTRAN, parentheses are not required. A pair of constants can be separated by spaces instead of a comma.

Null values on input are represented by two consecutive commas with no intervening constant(s). If a null value appears in the data, its corresponding list element will retain its old value and definition status.

When all the items in the I/O list have been assigned, any remaining input data is ignored.

A slash encountered in the input stream causes the current input statement to terminate. Any remaining items in the I/O list will retain their old values and definition status.

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The input values for List Directed Input can contain repetition groups of the form:

vc or v

where
v is the repetition factor
c is a constant

For example:
3*2.7, 2*, 2*'ABC'

which is the same as:
2.7, 2.7, 2.7, , , 'ABC', 'ABC'

Note:
Blanks are never used as zeros, and embedded blanks are not permitted in constants except within CHARACTER constants as described in the second point in the list above.

9.2.3.2 List-Directed Output¶

The form of the values produced is the same as that for input except in the cases of CHARACTER constants given here. The values are separated by one or more blanks.

CHARACTER constants are not delimited by apostrophes on output.

Each output record begins with a blank character to provide carriage control when the record is printed.

If successive values are identical, no replication factors are employed.

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The internal values are converted on output according to the formats:


I16	INTEGER
E16.7	REAL
D16.9	DOUBLE PRECISION
2E16.7	COMPLEX
A	CHARACTER
L16	LOGICAL (ND FORTRAN extension)
D16.9	NUMERIC

9.2.4 The READ Statement¶

The READ statement causes data to be transferred from external media to internal storage, or from an internal file to internal storage. The forms of read transfer are as follows:

UNFORMATTED READ TRANSFER¶

Form 1:

READ (u[,arglist])[iolist]

Note:
The form READ (u) will cause one unformatted input record to be skipped.

FORMATTED READ TRANSFER¶

Form 1:

READ f [,iolist]

Note:
This statement reads from the standard input device which can be set in the UNIT command, see Section 14.24.3 on page 295.

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Form 2:
```
READ (u,[f,arglist])[iolist]
```

Form 3 (List-directed)
```
READ (u,*[,arglist])[iolist]
```

where

u is a unit specifier see Section 9.1.3 on page 151.
f is the format specifier see Section 9.1.4 on page 152.
iolist, when present, is an input list specifying the data items whose values are to be transferred. A data item in an input list must be one of the following:
- a variable
- an array
- an array element
- a character substring

arglist is a list of optional items, separated by commas, in which each of the following items may appear no more than once:

Item	Section Reference
REC=rn	(see Section 9.1.8, on page 155)
IOSTAT=s	(see Section 9.1.7, on page 154)
ERR=label	(see Section 9.1.6, on page 154)
END=label	(see Section 9.1.5, on page 153)

If arglist contains a record specifier, the file should be opened for direct access. The specifier is ignored for sequential access. Arglist cannot contain both a record specifier and an end-of-file specifier.

If the format identifier is an asterisk, the statement is a list-directed input statement and a record specifier must not be present.

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In ND FORTRAN, the record specifier can be used with sequential access to reposition the file for READ or WRITE statements. Thus, the same part of the file can be read several times, and part of a file can be updated. For such an operation to be possible, the file must reside on a direct access device.

Also, in such a case it is permitted to specify both END= and REC= in the same arglist.

9.2.5 The WRITE Statement¶

The WRITE statement transfers data from internal storage to external media or from internal storage to internal files. The forms of write transfer are as follows:

UNFORMATTED WRITE TRANSFER¶

Form:

| WRITE (u[,arglist])[iolist] |

FORMATTED WRITE TRANSFER¶

Form 1:

| WRITE f[,iolist] |

Form 2:

| WRITE (u,f[,arglist])[iolist] |

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Form 3 (List-Directed):

WRITE (u, *[f, arglist]) [iolist]

where

u is a unit specifier (see Section 9.1.3 on page 151)
f is the format specifier (see Section 9.1.4 on page 152)
iolist, when present, is an output list identifying the data items whose values are to be transferred. A data item in an output list must be one of those:
- a variable
- an array
- an array element
- a character substring
- any other expressions except a character expression involving concatenation of an operand whose length specification is an asterisk in parentheses, unless the operand is the symbolic name of a constant.

arglist is a list of optional items, separated by commas, in which each of the following items may appear no more than once:

	Section Reference	Page Number
REC=rn	See Section 9.1.8	page 155
IOSTAT=s	See Section 9.1.7	page 154
ERR=label	See Section 9.1.6	page 154

If arglist contains a record specifier, the statement is a direct access output statement (See the READ statement earlier). If not, it is a sequential access output statement.

If the format identifier is an asterisk, the statement is a list-directed output statement and a record specifier is not allowed.

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9.2.5.1 Printing of Formatted Records¶

The transfer of information in a formatted record to certain devices determined by the processor is called printing. If a formatted record is printed, the first character of the record is not printed. The remaining characters of the record, if any, are printed on one line beginning at the left margin.

The first character of such a record determines vertical spacing as follows:

CHARACTER	VERTICAL SPACING BEFORE PRINTING	EXTERNAL OUTPUT
Blank	One line	LF record CR
0	Two lines	LF CR LF record CR
1	To first line of new page	FF LF record CR
+	No advance	record CR
$	No advance, CR suppressed	record

Note that the character $ in the above table is an ND FORTRAN extension. It can be used, for example, when writing to a terminal. The print head or cursor will remain at the end of the line, thus enabling answers to questions to follow on the same line.

Any other character occurring in the first position is treated as a blank.

If there are no characters in the record, the vertical spacing is one line and no characters other than blank are printed on that line.

A PRINT statement does not imply that printing will occur, and a WRITE statement does not imply that printing will not occur.

In ND-FORTRAN printing is used if the file is opened with ACCESS = 'PRINT' or 'PRINT-APPEND' or if the file is a PRINT file. The formatting must be different from List Directed Formatting.

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The following logical SINTRAN device numbers are PRINT files. All numbers are octal:

Less than 100 except:
- 3: fast punch
- 20 and 21: cassette
- 25, 33, 40, 41: magnetic tape controller 1
- 32, 34: magnetic tape controller 2
200 to 277: see SINTRAN manual ND 60.128
700 to 777: for descriptions
1040 to 1077
2000 to 2077
100 to 127: if they are spooling files

9.2.6 The PRINT Statement¶

The PRINT statement causes data to be transferred from internal storage to the standard output device. This can be defined by the UNIT command, see Section 14.24.3 on page 295. It is used only for sequential formatted data transfer. The PRINT statement takes the following forms:

Form 1:
```
PRINT f[,iolist]
```

Form 2:
```
PRINT*[,iolist]
```

where

f is the format specifier (see Section 9.1.4 on page 152)
iolist, if present, is the output list identifying the data items whose values are to be transferred.

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9.2.7 The INPUT Statement¶

In ND FORTRAN, list-directed input can be specified by the statement:

INPUT (u[,arglist])[iolist]

This is exactly equivalent to the list-directed form (Form 3) of the READ statement, see Section 9.2.4. on page 161.

9.2.8 The OUTPUT Statement¶

In ND FORTRAN, list-directed output can be specified by the statement:

OUTPUT (u[,arglist])[iolist]

This is exactly equivalent to the list-directed form (Form 3) of the WRITE statement, see Section 9.2.5. on page 163.

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9.3 FILE OPEN AND CLOSE¶

This section covers connecting and disconnecting files, creating them, and establishing parameters for I/O operations. The statements used for this are OPEN and CLOSE.

9.3.1 The OPEN Statement¶

The OPEN statement can connect an existing file to a unit, create a file that is preconnected, create a file and connect it to a unit, or change the specifiers of a connection between a file and a unit. It has the form:

OPEN (u[,arglist])

where

u is a unit specifier (see Section 9.1.3 on page 151)
arglist is a list of optional items, separated by commas, in which each of the following items appear no more than once:

Item	Specifier	Reference
IOSTAT	s	(Section 9.1.7, page 154)
ERR	label	(Section 9.1.6, page 154)
FILE	file
STATUS	sta
ACCESS	acc
FORM	fm
RECL	rl
BLANK	bl
PARITY	par	(ND FORTRAN Extension)
FIRSTREC	value	(ND FORTRAN Extension)
FACTOR	fac	(ND FORTRAN Extension)
IOCONVERT	ioco	(ND FORTRAN Extension)
TYPE	ty	(ND FORTRAN Extension)
MODE	seg	(ND FORTRAN Extension)
BUFFER-SIZE	bs2	(ND FORTRAN Extension)

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If the form UNIT= is used for the unit specifier, it may appear anywhere in arglist. If UNIT= is omitted, u must be the first specifier in the list.

When executing as RT programs (ND-100 only), all programs on a particular segment must use different unit numbers. Care should be taken when opening and using logical devices shared among programs on the same segment. Otherwise, there are no restrictions on the I/O facilities available to RT-programs.

To make the most efficient use of the various I/O options, refer to Chapter 15, Advanced FORTRAN Programming which begins on page 313.

The specifiers not previously described in arglist are described in the remainder of this section:

FILE = file¶

where

file is a character expression whose value is the name of the file acceptable to SINTRAN and is to be connected to the specified unit. The default file type is SYMB.

If no file is specified, the actual open monitor call is not executed, but the number must be within the range of legal unit numbers to OPEN (1-127), otherwise an error condition will occur.

If a file is specified, the unit number is used in subsequent I/O statements to refer to this file. If this is the case, the unit number must be positive and less than 128.

STATUS = sta¶

where

sta is a character expression whose value is old, NEW, SCRATCH or UNKNOWN. If OLD is specified, the file must exist; correspondingly, the file must not exist if NEW is specified. If the specifier is omitted, a value of UNKNOWN is assumed. If UNKNOWN is specified, the file is created if it does not exist.

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Successful execution of an OPEN statement with NEW specified creates the file and changes the status to OLD.

If SCRATCH is specified with an unnamed file, the file is connected to the specified unit for use by the executable program. The file is deleted at the execution of a CLOSE statement referring to the same unit or at the termination of the executable program.

In ND-FORTRAN named files are allowed to be used also if SCRATCH is specified. The file with specified name will be used (if it does not exist, it will be created). This file will be deleted by CLOSE statement or termination of the program.

ACCESS = acc¶

where

acc is a character expression whose value is one of the following:

SEQUENTIAL
DIRECT

and this determines the access method for the connection of the file. The default is SEQUENTIAL. SEQUENTIAL or DIRECT access should be used if the file is to be accessed through FORTRAN READ/WRITE statements.

Note:

If DIRECT or SEQUENTIAL access is used, the monitor call (76) SETBS must not be used for this file.

In ND FORTRAN the following values are also acceptable:

SPECIAL for use of monitor calls (i.e. SETBS, RFILE, WFILE or MAGTP)

Symbol	Description
W	Sequential output (WRITE statements)
R	Sequential input (READ statements)
WX	Random input or output (for RFILE/WFILE use)
RX	Random input (for RFILE use)
RW	Sequential input or output (READ/WRITE statements)

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Symbol	Description
WA	Sequential output appending to an existing file (WRITE statements)
WC	Random input or output to contiguous files (for RFILE/WFILE use)
RC	Random input from contiguous files (for RFILE use)
D	Random input or output direct (for RFILE/WFILE use)
DC	Random input or output direct closed (for RFILE/WFILE use, ND-500 only) Note: Direct closed means that such a file remains closed during all file transfers. FORTRAN does not set the maximum byte pointer for DC files.
READ	Random input (READ statements)
WRITE	Random input or output (READ/WRITE statements)
PRINT	Sequential output, first character interpreted as a forms control character (WRITE statement)
PRINT-APPEND	Sequential output appending to an existing file. First character interpreted as a form control character (WRITE statement).

FORM = fm¶

where

fm is a character expression with the value FORMATTED or UNFORMATTED. The value determines whether the file is being connected for formatted or unformatted I/O. The default with direct access is UNFORMATTED, with sequential access it is FORMATTED.

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RECL = rl¶

where

rl is an integer value which must be positive. It gives the length in characters (bytes) of each record, in the file to be connected for.

In ND FORTRAN, the RECL= specifier may always be used, whatever the value of the ACCESS= specifier.

In ND FORTRAN, SEQUENTIAL access used in conjunction with the RECL= specifier, may be used with either FORMATTED or UNFORMATTED I/O. Thus, all records in a SEQUENTIAL file can be made the same size. This, in turn allows the BACKSPACE statement to be used on an UNFORMATTED SEQUENTIAL file. The intention is that SEQUENTIAL files behave in the same way as DIRECT files, as far as the record size and structure are concerned, for both FORMATTED and UNFORMATTED files.

In FORMATTED files, data in a record is generally terminated by a CR LF (carriage return, line feed) pair of characters. In some cases, the physical record will be longer than the data plus the CR LF characters, and the rest of the physical record will be padded.

In ND FORTRAN, the record delimiter CRLF is included in the record. This means that the record must be specified as being two characters longer than the number of characters to be transferred. By using the compiler command: RUNTIME-STANDARD-MODE, you can avoid including the delimiters in the record. In either case, the information in the file and the number of bytes in the file are exactly the same.

If a FORMATTED file has a RECL= specifier in the OPEN statement, and data to be output is shorter than the specified record length, the record is padded with blanks.

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In ND FORTRAN, a record which is output and is shorter than the specified RECL value, will have undefined characters at the end of the record, as it is stored on a file. This applies to both FORMATTED and UNFORMATTED files. However, if a record is read from a FORMATTED file, it will be padded with blanks after the read operation.

If a FORMATTED file has a RECL= specifier in the OPEN statement, and data to be output is longer than the specified record length, the record is truncated.

In ND FORTRAN, in both FORMATTED and UNFORMATTED I/O with a RECL= specifier in the OPEN statement, a request to output more data than the RECL= specifier value, will result in a physical record being output, which is a multiple of the RECL= specifier value.

The following table summarizes the possible outcomes of I/O, in ND FORTRAN:

	RECL= specified	no RECL=
FORMATTED	data CR LF uuu	data CR LF
UNFORMATTED	data uuu	data

for ACCESS= DIRECT, SEQUENTIAL or SPECIAL

where

data is the record to be read or written by the program.
uuu is an undefined part of the record.

BUFFER-SIZE = bs2¶

where

bs2 is an integer value, which gives the number

of bytes in the buffer. The smallest value is 2048 bytes (1 page); the value must have a potence of 2. The BUFFER-SIZE used by FORTRAN can be smaller if there is not enough contiguous space in buffer pool. Use of bigger buffer is most effective for big contiguous files. In FORTRAN-100 this is a dummy parameter.

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BLANK = b1¶

where

b1 is a character expression whose value is NULL or ZERO. It is valid only for files being connected for formatted I/O and it determines the treatment of blanks. If NULL is specified, then all blank characters in numeric input fields are ignored (except that a field of all blanks has a value of zero). If ZERO is specified, then all blanks are treated as zeros. The default value is NULL.

The following specifiers are ND FORTRAN Extensions:

PARITY = par¶

where

par is a character expression which indicates how the "parity" bit is to be handled. The "parity" bit is the left-most bit of the character read or written. It applies only to formatted (including list-directed) transfers of data. The possible values and meanings are:

Value	Meaning
IGNORE	no action is taken on either input or output.
SET	the parity bit is set to zero on input, and to even parity on output. (This is compatible with the previous FORTRAN implementation.)
REMOVE	the parity bit is set to zero on input, but is left untouched on output.

If this parameter is not specified, the value is taken to be REMOVE unless the device is a terminal, in which it is taken to be SET.

REMOVE is supplied as an easy way of converting files from the old to the new form.

FIRSTREC = value¶

In ND FORTRAN, this option can be used to maintain compatibility with previous ND FORTRAN compilers with regard to the numbering of records for a direct access file.

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Value¶

Where value is an expression of type integer. Value determines the number assigned to the first record on a file. The default value, if the option is omitted, is 1. Previous compilers used 0 to indicate the first record. Only 0 and 1 are allowed as valid values; any other value will give unpredictable results.

FACTOR = fac¶

Where fac is an integer expression (with legal values of 1, 2, or 4). This parameter specifies the modification to the "amount" factor in the monitor calls SETBS, RFILE, WFILE, and MAGTP. The monitor calls have as argument(s) the length of the area read or written except for MAGTP function codes 26B and 27B where the amount is the exact number of bytes. The given amount parameters (or return parameters) in these monitor calls are adjusted by the value of fac before the monitor calls are executed.

A value of fac = 1 indicates that the amount parameter is to be interpreted as a number of bytes. fac = 2 means the number of 16-bit words, while fac = 4 means the number of 32-bit words. The default is fac = 2 for the ND-100 and fac = 4 for the ND-500, i.e. the number of words in both cases.

IOCONVERT = ioco¶

Where ioco is a character expression whose value is CONVERT or FORCE. The ioco parameter value indicates the handling of formatted I/O when either:

The I/O list element is of type REAL or COMPLEX, and the format specifier is an I
The I/O list element is of type INTEGER and the format specification is F, E or G.

A value of CONVERT indicates that a conversion REAL/INTEGER or INTEGER/REAL, is to take place if the specification would not otherwise apply.

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For the ND-500, and the ND-100 with the 32-bit floating-point option, a value of FORCE means that formatting is to be performed according to the format specification regardless of the type of the I/O list element (INTEGER4/REAL4). The default is FORCE.

It is an error to specify FORCE on an ND-100 with the 48-bit floating-point processor; the default here is CONVERT.

TYPE = ty
where

ty is a CHARACTER string. The first four characters (or the whole string if its length is less than four) are used to change the default SINTRAN file type from SYMB to some other value.

MODE = seg (ND-500 only)
where

seg is a CHARACTER string with the value SEGMENT

When SEGMENT is used it results in the file being used as a segment (ND-500 only). This will normally achieve more efficient I/O usage.

The use of this parameter will have no effect on the way a program executes, other than speed, providing only the following I/O statements are used:

READ, WRITE, ENDFILE, BACKSPACE, REWIND, OPEN and CLOSE.

Restriction:

No monitor call (in particular RFILE or WFILE) can be used for a file being used as a segment except for MON 416B (WSEGN).

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9.3.2 The CLOSE Statement¶

A CLOSE statement is used to terminate the connection of a file to a unit.

It has the form:

CLOSE (u[,arglist])

where

u is a unit specifier (see Section 9.1.3, on page 151)
arglist is a list of optional items, separated by commas, in which each of the following items may appear no more than once:
- IOSTAT = s (see Section 9.1.7, on page 154)
- ERR = label (see Section 9.1.6, on page 154)
- STATUS = sta

where sta is a character expression whose value is KEEP or DELETE.

The unit to be deleted must be explicitly specified. If unit in the following: CLOSE (unit, status = 'DELETE') has a negative value, no files are deleted.

In ND FORTRAN, the following values for u have special meanings:

Value	Meaning
-1	means close all files opened for this terminal, except those permanently opened.
-2	means close all files, even those permanently opened.
-3	means that all files opened by the ND-500 Monitor or the ND-500 program, will be closed.

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9.4 FILE POSITIONING¶

The statements used for positioning are BACKSPACE, ENDFILE and REWIND. The operations performed by these statements are normally used for sequential files on disk or magnetic tape devices.

9.4.1 The BACKSPACE Statement¶

The BACKSPACE statement will cause a file, connected to a specified unit, to be positioned at the start of the preceding record. If there is no preceding record, the file position remains unchanged.

If the specified unit is a file on disk, binary records can be backspaced only if the file is opened with fixed record length (RECL=n).

Format:

| BACKSPACE u |

or

| BACKSPACE (u[,arglist]) |

where

u is a unit specifier

In ND FORTRAN, a SINTRAN logical device number may be used instead of a unit specifier.

arglist is a list of the following optional items, separated by commas, as given below:

IOSTAT	= s (see Section 9.1.7 on page 154)
ERR	= label (see Section 9.1.6 on page 154)

If the file was opened with a RECL parameter, then this parameter is used to identify the position of the previous record. If the file is a formatted file, the statement will execute slowly unless RECL is specified.

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9.4.2 The ENDFILE Statement¶

The ENDFILE statement is used to write an endfile record as the next record of the file. This record will define the end of the file that contains it.

Format:

   ENDFILE u

or

   ENDFILE [u[,arglist]]

where u is a unit specifier.

In ND FORTRAN, a SINTRAN logical device number may be used instead of a unit specifier.

arglist is a list of the following optional items, separated by commas, as given below:

IOSTAT	= s	(see Section 9.1.7 on page 154)
ERR	= label	(see Section 9.1.6 on page 154)

After execution of an ENDFILE statement, a BACKSPACE or REWIND statement must be used to reposition the file prior to execution of any data transfer I/O statement.

Note:

An ENDFILE statement will not automatically be performed before rewinding.

9.4.3 The REWIND Statement¶

Execution of a REWIND statement causes the specified file to be positioned at its initial point (the load-point mark on a magnetic tape). If the file is already positioned at its initial point, execution of this statement has no effect on the position of the file.

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Format:¶

REWIND u

or

REWIND (u[,arglist])

where
u is a unit specifier

In ND FORTRAN, a SINTRAN logical device number may be used instead of a unit specifier.

arglist is a list of the following optional items, separated by commas, as given below:

Item	Description
IOSTAT	= s (see Section 9.1.7 on page 154)
ERR	= label (see Section 9.1.6 on page 154)

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9.5 THE INQUIRE STATEMENT¶

The INQUIRE statement may be used to inquire about properties of a particular named file or of the connection to a particular unit.

The INQUIRE statement may be executed before, during, or after a file is connected to a unit. All values assigned by the INQUIRE statement are those that are current at the time the INQUIRE statement is executed.

The two forms of the INQUIRE statement are:

INQUIRE by file:
```
INQUIRE(FILE=filename[,arglist])
```
where
- filename is a character expression whose value, when any trailing blanks are removed, specifies the name of the file being inquired about.
- arglist is a list of optional specifiers, taken from the table given on the next page. The specifiers must be separated by commas, and each may occur no more than once.

The specifier FILE= may appear anywhere in arglist.

INQUIRE by unit:
```
INQUIRE(u[,arglist])
```
where
- u is a unit specifier (see Section 9.1.3 on page 151)
- arglist is a list of optional specifiers taken from the table given on the next page. The specifiers must be separated by commas, and each may occur no more than once.

If the form UNIT= is used for the unit specifier, it may appear anywhere in arglist. If UNIT= is omitted, u must be the first specifier in the list.

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The following inquiry specifiers may be used in either form of the INQUIRE statement, i.e. for arglist above:

Specifier	Abbreviation	Reference
IOSTAT	s	(see Section 9.1.7, page 154)
ERR	label	(see Section 9.1.8, page 154)
ACCESS	acc
BLANK	blnk
DIRECT	dir
EXIST	ex
FORM	fm
FORMATTED	fmt
NAME	fn
NAMED	nmd
NEXTREC	nr
NUMBER	num
OPENED	od
RECL	rcl
SEQUENTIAL	seq
UNFORMATTED	unf

The specifiers are described in the rest of this chapter:

ACCESS=acc

where

acc is a character variable or a character array element.

acc will be assigned the value SEQUENTIAL if the file is connected for sequential access, or the value DIRECT if the file is connected for direct access.

If there is no connection, acc becomes undefined.

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BLANK=blnk¶

where

blnk is a character variable or a character array element.

blnk will be assigned the value NULL if null blank control is in effect for a file connected for formatted I/O, or the value ZERO if zero blank control is in effect for a file connected for formatted I/O.

If there is no connection, or if the connection is not for formatted I/O, blnk becomes undefined.

DIRECT=dir¶

where

dir is a character variable or a character array element.

dir will be assigned the value YES if DIRECT is one of the allowed access methods for the file, or the value NO if DIRECT is not one of the allowed access methods for the file.

If it is not possible to determine whether DIRECT is allowed as an access method for the file, dir will be assigned the value UNKNOWN.

EXIST=ex¶

where

ex is a logical variable or a logical array element.

For INQUIRE by file, ex will be assigned the value .TRUE. if the file with the specified file name exists, or the value .FALSE. otherwise.

For INQUIRE by unit, ex will be assigned the value .TRUE. if the specified unit exists, or the value .FALSE. otherwise.

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FORM=fm¶

where

fm is a character variable or a character array element.

fm will be assigned the value FORMATTED if the file is connected as formatted I/O, or UNFORMATTED if the file is connected for unformatted I/O.

If there is no connection, fm becomes undefined.

FORMATTED=fmt¶

where

fmt is a character variable or a character array element.

fmt will be assigned the value yes if formatted is an allowed form for the file, or the value NO if FORMATTED is not an allowed form for the file.

If it is not possible to determine whether FORMATTED is an allowed form for the file, fmt will be assigned the value UNKNOWN.

NAME=nme¶

where

nme is a character variable or a character array element.

nme will be assigned the name of the file being inquired about, i.e. the file named in the FILE= specifier, or connected by a UNIT= specifier.

The value assigned to nme will not necessarily be identical to the name in the FILE= specifier. The value assigned to nme is a fully qualified file name, which is suitable for use in the FILE= specifier of the OPEN statement.

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In ND FORTRAN, the value assigned to nme is made up of, (directory:user)name:type;version, while the name used in the FILE= specifier may be an abbreviated form of the name, using the usual rules for abbreviation.

NAMED=nmd¶

where

nmd is a logical variable or a logical array element.

nmd will be assigned a value .TRUE. if the specified file has a name, or the value .FALSE. otherwise.

NEXTREC=nr¶

where

nr is an integer variable or an integer array element.

nr will be assigned an integer value, plus one, of the record number of the last record read, or written, to a file connected for direct access. If the file is connected, but no records have been read or written, nr will be assigned to 1.

If the file is not connected for direct access, or the position of the file is indeterminate because of a previous error condition, nr becomes undefined.

NUMBER=num¶

where

num is an integer variable or an integer array element.

num will be assigned the value of the unit currently connected to the specified file.

If there is no unit connected to the specified file, num becomes undefined.

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Note:

If the form of the INQUIRE statement is inquired by file, and the UNIT= specifier is set to -1, then the NUMBER= specifier will be assigned the SINTRAN logical device number.

OPENED=od

where

od is a logical variable or a logical array element.

od will be assigned the value .TRUE. if either the specified file (specified by the FILE= specifier) or the unit specified unit, is currently open, or the value .FALSE. if the file or unit is not open.

RECL=rcl

where

rcl is an integer variable or an integer array element.

rcl will be assigned the value of the record length of a file connected for direct access. The value is in bytes, whether the file has been connected for formatted or unformatted I/O.

If the file is not connected, or if the file is connected for other than direct access, rcl becomes undefined.

In ND FORTRAN, the RECL= specifier in the INQUIRE statement is always defined if the RECL= specifier in the corresponding OPEN statement is defined.

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SEQUENTIAL=seq¶

where

seq is a character variable or a character array element.

seq will be assigned the value YES if sequential is one of the allowed access methods for the file, or the value NO if SEQUENTIAL is not one of the allowed access methods for the file. If it is not possible to determine whether SEQUENTIAL is allowed as an access method for the file, seq will be assigned the value UNKNOWN.

UNFORMATTED=unf¶

where

unf is a character variable or a character array element.

unf will be assigned the value YES if UNFORMATTED is an allowed form for the file, or the value NO if UNFORMATTED is not an allowed form for the file.

If it is not possible to determine whether UNFORMATTED is an allowed form for the file, unf will be assigned the value UNKNOWN.

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Format Specifications¶

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A format used in conjunction with formatted I/O statements provides information that directs the editing between the internal representation and the character strings of one or a sequence of records in the file.

A format specification provides explicit editing information. An asterisk (*) as a format identifier in an I/O statement indicates list-directed input/output, see Section 9.2.3 on page 158.

10.1 FORMAT SPECIFICATION METHODS¶

Format specifications may be given either:

in FORMAT statements, or
as arrays of CHARACTER strings, CHARACTER variables, or other CHARACTER expressions.

The FORMAT statement has the form:

| FORMAT (F1, F2, F3, ......, Fn) |

where

F1, F2,... etc. are format descriptors, described in the next section.

The comma used to separate the descriptors may be omitted in the following circumstances:

before or after a slash or colon format descriptor
between a P format descriptor and an F, E, D, or G descriptor which follows immediately after it

The FORMAT statement must be labeled.

With character format specifications, as in the second instance above, the expression must contain format descriptor(s) enclosed in parentheses.

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10.2 FORMAT DESCRIPTORS¶

These descriptors describe the record structure of the data, the format of the fields within the record, and the conversion, scaling and editing of data within specific fields. A list is given on the following page.

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DESCRIPTORS	COMMENTS
rFw.d	Floating-point numeric field descriptors
rEw.d
rEw.dEe
rDw.d
rGw.d
rGw.dEe
rIw	INTEGER field descriptors
rIw.m
rJw	(ND FORTRAN Extension)
rLw	LOGICAL field descriptor
rA	Alphanumeric data field descriptor
rAw
rOw	Octal format descriptor (ND FORTRAN Extension)
rZw	Hexadecimal format descriptor (ND FORTRAN Extension)
nHs	Text descriptors
'text'
text	(ND FORTRAN Extension)
rX	Field formatting descriptor
kP	Numerical scale factor descriptor
:	Format control terminating descriptor
/	Record delimiting descriptor
Tc	Positional editing descriptors
TLc
TRc
S	Optionally positive sign editing descriptors
SP
SS
BN	Blank interpretation descriptors
BZ

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Explanation¶

r is a repetition factor and is a nonzero unsigned integer constant.

d and m are unsigned integer constants.

w, e, n and c are nonzero unsigned integer constants.

k is an optionally signed integer constant.

s is a string of characters.

Note: w is known as the field width and is the size in characters of the field, the part of a record read on input or written on output under the control of a format specification.

In addition, repetition of groups of format descriptors can be achieved by parentheses, e.g. r(F1, F2, ..., Fn) where Fi are format descriptors.

In ND FORTRAN the maximum depth of nesting of these parentheses is 5.

The following sections provide detailed descriptions of the various types of format descriptors and the manner in which they are written and employed.

10.2.1 Interaction between the Format Descriptors and the I/O List¶

The execution of an I/O statement specifying a formatted data transfer operation will initiate format control. The contents of the I/O list and the format specifications are scanned in step. Whenever format control encounters a repetition factor in a format descriptor, it determines whether there is a corresponding item in the I/O list. If there is, it transmits appropriately edited information between the item and the record. If not, format control terminates.

A list item of type complex will require two corresponding format descriptors of type F, E, D, or G.

For P, X, T, TL, TR, S, SP, SS, H, BN, BZ, slash, colon, or text format descriptors there are no corresponding items in the I/O list, and format control communicates

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Information directly to or from the record.

If format control encounters the rightmost parenthesis of a complete format specification and another list item is not found, format control terminates. It also terminates if a colon descriptor is encountered in the format specification and another list item is not found.

If the end of the format specification is reached and more items remain in the list, a new record is established and the scan process is restarted. It restarts either at the first item in the format specification or, if parenthesised, with the last set of descriptors within the format specification. (That is, restarting at the first left parenthesis to the left in the format specification just acted upon.)

A record is terminated by one of the following:

A slash format descriptor.
The rightmost parenthesis of the FORMAT.
The end of the I/O list is encountered, and the rest of the format descriptors require I/O list items.
A colon descriptor is encountered, and there are no more items in the I/O.

On input, only a single slash, /, will cause an additional record to be read. A record is skipped when two slashes, //, are encountered or a slash is followed by the end of the format specifications.

If the record ends, due to the end of the format specifications or a slash within them, then any data left in the input record is ignored. If the input record is exhausted before the data transfers are completed, then the transfer proceeds as if the record were extended with blanks.

On output, an additional record is written only when a slash, /, is encountered in the format specifications. Two consecutive slashes or one slash followed by the end of the specifications will cause an empty record to be written.

If the file is an internal file, then a record is determined by the length of the internal data item. For non-CHARACTER arrays, and for CHARACTER variables, the file contains just one record. For CHARACTER arrays, each element is a record, the order of access being the same as the order of implied subscripting, with the first subscript varying most rapidly.

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10.2.2 Editing Provided by the Format Descriptors¶

10.2.2.1 Numeric Editing¶

The I, F, E, D and G descriptors are used for the I/O of INTEGER, REAL, DOUBLE PRECISION and COMPLEX data. The following rules apply:

On input, leading blanks are not significant. The interpretation of other blanks depends on whether any BLANK = (see the OPEN statement) specifier and whether any BN or BZ control is currently in effect. Plus signs may be omitted. A field of all blanks is considered to be zero.

On input, with F, E, D and G editing, a decimal point appearing in the input field overrides its specification in a format descriptor.

On output, the representation of a zero or positive value in the field may be prefixed with a plus, as controlled by the S, SP and SS descriptors. A negative internal value will be prefixed by a minus in the field.

On output, the representation in the field is right justified. After editing, if the number of characters is less than the field width, leading blanks will be inserted. If the number of characters exceeds the field width then the entire field of width w is filled with asterisks.

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10.2.2.2 The I and J Format Descriptors¶

The Iw, Iw.m, and Jw descriptors are for INTEGER editing, where the field for editing occupies w positions. The specified I/O list item must be of type INTEGER.

In ND FORTRAN, if the list item is of type REAL, DOUBLE PRECISION or COMPLEX, then the editing will be performed according to the IOCONVERT specifier in the OPEN statement.

In ND FORTRAN, the Iw descriptor can also be used for editing items of type NUMERIC.

In the input field, the character string must be in the form of an optionally signed integer constant. On input an Iw.m descriptor is treated identically to an Iw descriptor.

The output field for the Iw descriptor will consist of leading blanks, if any, a minus sign if the internal value is negative, or an optional plus if the internal value is positive. This is followed by the magnitude of the internal value expressed as an unsigned integer constant and must consist of at least one digit.

The output field for the Iw.m descriptor is the same as for the Iw descriptor except that the unsigned integer constant consists of at least m digits and, if necessary, leading zeros. The value of m must not be greater than w. If it is zero and the internal value is also zero, the output field will consist only of blanks, regardless of sign control.

In ND FORTRAN, the Jw is treated like Iw except that there is no zero suppression at the start of the output field. If a sign is to be output, it occupies the first position, otherwise a digit fills this place.

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Examples:

VALUE	FORMAT	OUTPUT
1	I1	1
1234	I5	1234
-1234	I5	-1234
0	I5	0
1234	I5.0	1234
0	I5.0
12	I5.4	0012
-12	I5.4	-0012
0	I5.4	0000

10.2.2.3 REAL and DOUBLE PRECISION¶

The F, E, D and G format descriptors specify the editing of REAL, DOUBLE PRECISION, and COMPLEX data. An I/O list item corresponding to one of these descriptors must also be REAL, DOUBLE PRECISION or COMPLEX.

In ND FORTRAN, if the list item is of type INTEGER, then the editing will be performed according to the IOCONVERT specifier in the OPEN statement.

In ND FORTRAN, the F, E and D descriptors can also be used for editing items of type NUMERIC.

10.2.2.4 The F Format Descriptor¶

The Fw.d descriptor implies that the field contains w positions, the fractional part of which consists of d digits.

The input field consists of an optional sign, followed by a string of digits optionally containing a decimal point. If there is no decimal point, the rightmost digits are interpreted as the fractional part of the value. The basic form may be followed by an exponent of the form:

Signed integer constant, or
E followed by zero or more blanks, followed by an optionally signed integer constant, or
D followed by zero or more blanks, followed by an optionally signed integer constant.

An exponent containing an E is processed identically to an exponent containing a D.

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The output field consists of blanks, if necessary, followed by a minus if the internal value is negative, or an optional plus otherwise. This is followed by a string of digits containing a decimal point and representing the magnitude of the internal value, modified by any established scale factor, and rounded to d digits. Leading zeros are suppressed up to the decimal point, i.e. if the value lies between zero and one, the first non-blank character represents the position of the decimal point.

Examples:

VALUE	FORMAT	OUTPUT
1.2	F5.0	1.
-1.2	F5.0	-1.
1.2	F5.1	1.2
0.4	F5.2	.40
-0.4	F5.2	-.40
0.	F5.2	.00
1.	F5.2	1.00
-1.	F5.2	-1.00

10.2.2.5 Scale Factor: The P Format Descriptor¶

The P format descriptor specifies the scale factor in the form:

kP

where

k is called the scale factor and is an optionally signed constant.

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The value of the scale factor is zero at the beginning of execution of each I/O statement. It applies to all subsequently interpreted F, E, D and G descriptors until another scale factor is encountered. It has the following effect upon the editing:

With F, E, and D format descriptors on input (provided that no exponent exists in the field) and the F format descriptor on output, the externally represented number equals the internally represented number multiplied by 10 * * k.

On input, with F, E, D and G format descriptors, the scale factor has no effect if there is an exponent in the field.

On output, with E and D format descriptors, the basic real constant part of the quantity (optional sign, integer part, decimal point and fractional part) is multiplied by 10 * * k. The exponent is reduced by k.

On output, with G editing, the scale factor has no effect unless the magnitude of the value is outside the range for F editing. If the use of E editing is required, the scale factor has the same effect as using the E format descriptor on output.

Example:¶

REAL REALARR (4)
100 FORMAT (1X, F12.4, 2PF12.4, F12.4, -2PF12.4)
200 FORMAT (1X, E12.4, 1X, 2PE12.4, 1X, -1PE12.4, 1X, OPE 12.4)
300 FORMAT (1X, 4F12.4, ///)
400 FORMAT (1X, 4 (E12.4, 1X))
500 FORMAT (F12.4, 2PF12.4, -1PF12.4, -2PF12.4)
600 FORMAT (E12.4, 2PE13.4, -1PE13.4, OPE13.4)
READ (1,500) REALARR
WRITE (1,100) REALARR
WRITE (1,300) REALARR
READ (1,600) REALARR
WRITE (1,200) REALARR
WRITE (1,400) REALARR

Input and Output With F Editing:¶


1.6	.16E+1	160.E-2	1.6
1.6000	160.0000	160.0000	1.6000
1.6000	1.6000	1.6000	160.0000

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Input and Output With E Editing:¶

2.5	.25E+1	2.5	250.E-2
.2500E+01	25.000E-01	.0250E+03	.2500E+01
.2500E+01	.2500E+01	.2500E+02	.2500E+01

10.2.2.6 The E and D Format Descriptors¶

The Ew.d, Dw.d and Ew.dEe descriptors indicate that the external field occupies w positions, the fractional part of which consists of d digits (unless a scale factor of greater than one is in effect) and the exponent part consists of e digits. The e has no effect on input.

The form of the input field is the same as that for the F format descriptor described above.

With a zero scale factor the form of the output would be:

[ \pm ] . X₁ X₂ ----Xd exp

X₁ X₂ ----Xd being the d; most significant digits after rounding.

exp is a decimal exponent, which for the value 76 or less will be of the form:

E ± n₁ n₂

or (for Dw.d descriptors only):

D ± n₁ n₂

where

n is a decimal digit.

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For the Ew.dEe descriptor, the form of the exponent is:

E ± n₁ n₂ --- ne

where the absolute value of the exponent must be:

≤ (10 * * e) - 1

The scale factor k, described above, controls the decimal normalization.

There are two cases to consider:

-d < k ≤ 0. The output field will contain (taking the absolute value of k) k leading zeros and d-k significant digits after the decimal point.
0 < k < d + 2. The output field will contain k significant digits to the left of the decimal point and d-k+1 significant digits to the right of the decimal point.

Other values of k are not accepted.

Examples:

VALUE	FORMAT	OUTPUT
0	E12.4	.0000E+00
123	E12.4	.1230E+03
-123	E12.4	-.1230E+03
123	E12.4E1	.1230E+3
-123	E12.4E1	-.1230E+3

10.2.2.7 The G Format Descriptor¶

The Gw.d and Gw.dEe descriptors indicate that w is the width of the external field, the fractional part of which contains d digits unless a scale factor of greater than one is in effect. The exponent part consists of e digits.

On input, the editing performed by the G format

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The descriptor is the same as that for F described earlier.

On output, the editing depends on the magnitude of the internal value, N, in the following way:

If N < 0.1 or N > 10^d, then editing performed by Gw.d on output is the same as that by kPEw.d, and for Gw.dEe the result is the same as that when using kPEw.dEe.

If 0.1 ≤ N < 10^d, k (the scale factor) has no effect and the results depend upon N as given below where F is the format descriptor, and n takes the value 4 with the Gw.d descriptor or e+2 for the Gw.dEe descriptor:

N	Conversion Type
0.1 ≤ N < 1	F(w-n).d
1 ≤ N < 10	F(w-n).d-1
10^(d-2) < N < 10^(d-1)	F(w-n).1
10^(d-1) < N < 10^d	F(w-n).0

The output field will be followed by n blanks.

Note that the scale factor has no effect unless N is outside the range of values for effective F editing.

10.2.2.8 COMPLEX Data¶

Since this consists of separate pairs of real values the editing is specified by two successive F, E, D, or G format descriptors.

The first descriptor will specify the real part, the second the imaginary part. The two descriptors may be different and other non-repeatable descriptors may appear between them.

10.2.2.9 S, SP and SS Format Descriptors¶

These edit descriptors are used to control the optional plus signs in the output fields.

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If none of the edit descriptors are used, then optional plus signs will not be printed.

If an SP descriptor is encountered in a format specification, then subsequent optional plus signs will be printed.

If an SS or S descriptor is encountered, then further optional plus signs will not be printed.

10.2.2.10 The BN and BZ Format Descriptors¶

These descriptors specify the interpretation of non-leading blanks in numeric input fields. Such blank characters, at the beginning of the input statement execution, are interpreted as zeros or are ignored, depending upon the BLANK=specifier in the OPEN statement in effect.

Upon encountering a BN descriptor in the format specification, the non-leading blanks referred to above will be ignored.

The effect of a BZ descriptor is to treat all such blanks as zeros.

BN and BZ affect the I, F, E, D, G, O and Z editing during input.

10.2.2.11 The Text Format Descriptor¶

This descriptor has the form 'text' which is equivalent to a character constant. It causes a character string (which may include blanks) to be written from the enclosed characters of the format descriptor itself. An apostrophe edit descriptor is not valid on input. The width of the field is the number of characters between the delimiting apostrophes, but not including the apostrophes themselves.

ND FORTRAN has an alternative form: text.

If the asterisk is used as the text delimiter, then a quote is treated as just another character. Correspondingly, if the delimiter is a quote, then the asterisk is treated as an ordinary character.

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10.2.2.12 The H Format Descriptor¶

The descriptor has the form:


nHs

It causes the n characters forming the string s to be written on the output stream.

In ND FORTRAN the form Hs may be used for a single character.

An H descriptor must not be used on input.

10.2.2.13 The T, TL, TR, and rX Format Descriptors¶

These descriptors control positional editing and specify at which position the next character will be transmitted to or from the record.

The position indicated by a T descriptor may be in either direction from the current position. On input, this allows parts of a record to be processed more than once, possibly with different editing.

On output, since this group of descriptors do not themselves cause characters to be transmitted, they do not affect the length of the record. If characters are transmitted to or beyond the position specified positions skipped are filled with blanks. The result is as if the whole record were initialized with blanks.

In the Tc format descriptor, c is the character position to which, or from which the record transmission of the next character is to occur.

With the TLc descriptor, the transmission is to occur at a position c characters backward from the current one. (If the current position should be c, the transmission to or from will start from position 1 (one) of the record.)

With the TRc descriptor, the transmission will occur at a position c characters forward from the present one.

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The rX format descriptor causes the transmission of the next character to or from a record to occur at a position r characters forward from the current position. On input this position may be beyond the last character of the record so long as no characters are transmitted from such positions.

In ND FORTRAN, r can be omitted and 1 will be assumed as its value.

10.2.2.14 The Slash, /, Format Descriptor¶

This descriptor denotes the end of data transfer on the current record. The following will occur:

On input from a sequential file, the remaining portion of the record is skipped and the next record becomes the current record.

On output to a sequential file, a new record is created and becomes the last and current record of the file.

For a direct access file, the record number i is increased by one and the file is positioned at the beginning of the record having that number. This record becomes the current record.

In ND FORTRAN, the slash format descriptor can be preceded by a replication factor.

10.2.2.15 The L Format Descriptor¶

This descriptor has the form:

Lw

where
w indicates that the field occupies w positions. The corresponding I/O list item must be of type LOGICAL.

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The input field consists of optional blanks, optionally followed by a decimal point, followed by T for true or F for false. T or F may have additional characters following them in the field.

The output field consists of w-1 blanks followed by T or F according to whether the value of the internal LOGICAL variable has the value .TRUE. or .FALSE.

10.2.2.16 The A Format Descriptor¶

The A [w] format descriptor is used with CHARACTER I/O list items.

If the optional field width w is used then the field consists of w characters. If w is not specified, then the number of characters in the field is the same as the length of the I/O list item.

Let l be the length of the I/O list item. On input, if

| w > l |

then the rightmost l characters will be taken from the input field. If however:

| w < l |

w characters will appear left justified with l-w trailing blanks.

On output, if:

| w > l |

the output field will consist of w-l blanks followed by l characters from the internal representation. If, however:

| w < l |

the output field will consist of the leftmost w characters of the internal representation.

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Example:¶

VALUE	FORMAT	OUTPUT
'ABCDE'	A	ABCDE
'PQRST'	A3	PQR
'PQRST'	A8	bbbPQRST

where
b represents a space character (blank).

10.2.2.17 The O Format Descriptor¶

In ND FORTRAN this descriptor is used for octal I/O for any of the data types - INTEGER, REAL or DOUBLE PRECISION.

On input, w characters from the input record are treated as an octal number. The bit representation of the binary value is then placed, unconverted, in the list item, right-justified and truncated or padded with zeros on the left.

Example:¶

The following example is on an ND-100 with 48-bit floating-point hardware:

INPUT (Octal)	FORMAT	INTERNAL VALUE (INTEGER*2) (octal)
137326	06	137326
2671	06	002671
37533235	08	133235 (REAL*6)

| | 016 | 040003 100000 000002 | | 200016000000000002 | | |

On output, the internal bit representation is treated as an unsigned binary integer and is output right-justified with truncation or padding with blanks on the left in a field of width w.

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10.2.2.18 The Z Format Descriptor¶

In ND FORTRAN this descriptor is used for hexadecimal I/O for any of the data types: INTEGER, REAL or DOUBLE PRECISION.

On input, w characters from the input record are treated as a hexadecimal number. The bit representation of the binary value is then placed, unconverted, in the list item, right-justified and truncated or padded with zeros on the left.

For example:

INPUT (Hexadecimal)	FORMAT	INTERNAL VALUE (INTEGER*4) (decimal)
2186E	Z6	137326
A67	Z6	2671
F0000001	Z9	1
		Value (REAL*8)
4050000000000000	Z16	1.0

On output, the internal bit representation is treated as an unsigned binary integer and is output right-justified with truncation or padding with blanks on the left in a field of width w.

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Chapter 11¶

Functions and Subroutines¶

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FUNCTIONS AND SUBROUTINES¶

Functions and subroutines (also known as subprograms) are procedures which can be called from within a program as many times as required. These procedures may be either internal (contained within the program in which they are referenced) or external (self-contained executable procedures that may be compiled separately).

These are the categories of procedures:

Intrinsic functions
Statement functions
External functions
Subroutines

The first three categories are referred to collectively as functions. The last two, subroutines and external functions, are both referred to as external procedures.

Section 11.2.2 contains a table of all the INTRINSIC functions, including those defined in ANSI FORTRAN 77 and a number of extra functions implemented in ND FORTRAN. Appendix D contains descriptions and a table of functions or subroutines of a more general nature, provided in the FORTRAN library. Appendix C contains complete descriptions of all the available Monitor Calls, i.e., services provided by the operating system.

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11.1 DUMMY AND ACTUAL ARGUMENTS¶

Some of the entities used by functions and subroutines may vary from one call to another. Such entities are represented by dummy arguments of the same type and are given in the form of a list associated with the subprogram identifier. The actual arguments, i.e., the values the entities are to take for a particular reference to the subprogram, are given in a corresponding list associated with this reference.

Example:

A function to evaluate the arithmetic mean (average) of two real numbers could be defined as:

FUNCTION AVER (A, B)
AVER = (A+B) / 2.0
RETURN
END

The first statement defines AVER as a function and indicates that it has two dummy arguments, A and B. The second statement demonstrates how to evaluate the function. The third statement shows that control is complete and is to return to the routine or program which invoked this function. The END statement indicates that the definition of this function is complete. These statements are discussed in more detail later in the chapter.

To use the function to calculate an average, the following could be written:

P=AVER(X, Y)

where

X and Y are the actual arguments in this invocation. The statement demonstrates the invocation of AVER and the assignment of the resulting function value to P. The actual argument X is associated with the dummy argument A, and the actual argument Y with the dummy argument B.

The result, as defined above, is (A+B)/2.0 which, in this case, is (X+Y)/2.

The result can be used as part of an expression in the same manner as any other operand.

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For example:¶

P=Q+AVER(1.0, T+V) * S

which evaluates the average of the constant 1.0 and T+V. It then multiplies the result by S, adds Q, and puts the resulting sum in P.

Actual arguments may be constants (or their symbolic names), function references, expressions involving operators, and expressions enclosed in parentheses, if and only if the associated dummy argument is 'read-only', i.e. its value is not changed by the subprogram.

The type of each actual argument must agree with the type of its associated dummy argument except when the actual argument is a subroutine name, see Section 11.5, on page 242 or an alternate return argument on Section 11.7 on page 248.

Example:¶

In the previous example demonstrating the AVER function, neither A nor B are in any way changed by the execution of AVER, consequently the use of constants and expressions is in order.

However, suppose a function called NEXTIN is defined to read the next number from a file, and returns this number in the dummy argument. Furthermore, it is a LOGICAL function and indicates whether the next value was read, by returning .TRUE. if that was the case, or .FALSE. if not. All the numbers on the file can be summed as follows:

S=0
10 IF (NEXTIN(X)) THEN
    S=S+X
    GO TO 10
ENDIF

Note: In ND FORTRAN this could be written more neatly as:

S=0
DO WHILE (NEXTIN(X))
    S=S+X
ENDDO

Since NEXTIN returns a value in its dummy argument, it is illegal to write NEXTIN (A + 1) or NEXTIN (35*2) as there would be nowhere to set the value that NEXTIN reads.

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However, an array can be used for reading into, as follows:

DIMENSION A (1000)
DO 10 I=1,1000
    IF (.NOT.NEXTIN(A(I))) GO TO 20
10 CONTINUE
20 CONTINUE
C HERE I CONTAINS THE INDEX BEYOND THE LAST ONE READ.

Upon execution of a function or subroutine reference, an association is established between the corresponding actual and dummy arguments. The first dummy argument becomes associated with the first actual argument, the second with the second and so on.

Argument association may be carried through more than one level of procedure reference.

Argument association within a program unit terminates when a RETURN or END statement in the program unit has been executed.

Length of Character Dummy and Actual Arguments¶

For a character-type dummy argument, the associated actual argument (also of type character) must have a length equal to or greater than that of the dummy argument. When the lengths differ, if e is the length in characters of the dummy argument, then the e leftmost characters of the actual argument become associated with the dummy argument.

For an array name, the restriction on length is for the entire array and not for each array element.

Example:

In the subroutine:

SUBROUTINE PRNAME (NAME)
CHARACTER NAME*20
WRITE (OUT, '(5X, A)') NAME
END

there is a character dummy argument that is assumed to be of an exact length of 20, and it will write 20 characters on the file whatever the actual argument.

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Thus if we have:

CHARACTER ALPHA*26
DATA ALPHA='ABCDEFGHIJKLMNOPQRSTUVWXYZ'

then:

CALL PRNAME (ALPHA (7:))

will cause the characters 'G' to 'Z' to be written.

If the intention is to write out exactly the actual argument, then the appropriate declaration of the dummy argument is:

CHARACTER NAME*(*)

Dummy and Actual Argument of Type NUMERIC¶

Normally, dummy and actual arguments have to be declared with the same field width and scaling factor. In this case there is no restriction in mixed arithmetic.

It is possible to declare a dummy argument of type NUMERIC without specifying field width and scaling factor.

Example:

SUBROUTINE S(N)
NUMERIC (*) N

In this case, the dummy argument may not be used in mixed arithmetic.

11.1.1 Variables as Dummy Arguments¶

A dummy argument that is a variable may be associated with an actual argument that is a variable, array element, substring, or expression.

The dummy argument may be defined or redefined with the subprogram if the actual argument is:

a variable name
an array element name
a substring name

If, however, the actual argument is:

a constant (or the symbolic name of a constant)
a function reference

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an expression involving operators
an expression enclosed in parentheses

then the dummy argument must not be redefined within the program.

11.1.2 Arrays as Dummy Arguments¶

The number and size of dimensions of an array in an actual argument may differ from those of an array in an associated dummy argument.

If the actual argument is an array name, then the association between actual and dummy arguments occurs as if the first element of the actual argument were the actual argument.

If the actual argument is an array element name then the dummy argument is associated with an array whose first element is the actual argument.

The dummy argument must be wholly contained within the actual argument.

Example:

Suppose there is a function defined to compute the arithmetic mean (average) of an array. It contains two dummy arguments, the array and the number of elements in the array.

Thus:

FUNCTION ARMEAN (A, N)
DIMENSION A (1:N)
C ADD UP THE ARRAY FIRST, THEN DIVIDE BY THE NUMBER OF C ELEMENTS
R=0
DO 10 I= 1, N
  R=R+A(I)
10 CONTINUE
ARMEAN = R/N
RETURN
END

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This function can be used to find the arithmetic mean of whole arrays or parts of them, provided the parts are contiguous. If we have, for example:

DIMENSION AGES (1:100), SIZES (1:50, 1:50)

then the average of all ages is:

ALLAGE=ARMEAN (AGES, 100)

or, the first 10 ages would be given by:

FIRST=ARMEAN (AGES (1), 10)

or, the last 10 ages (91 to 100 inclusive):

FINAL = ARMEAN (AGES (91), 10)

But the mean of the second, fourth, sixth ... etc., elements cannot be computed since they are not contiguous.

When using a two-dimensional (or higher) array, the dummy argument is associated with contiguous locations in the actual argument, i.e. the first subscript varies most rapidly. Thus, clearly:

ALLSIZE=ARMEAN (SIZES, 50*50)

will compute the mean of all sizes, but:

SINGLE=ARMEAN (SIZES (1, 1), 50)

will examine SIZES (1, 1), SIZES (2, 1), SIZES (3, 1)... SIZES (50, 1).

11.1.3 Procedures as Dummy Arguments¶

A dummy procedure is a dummy argument identified as a procedure. An example of its use is given below.

Example:

If a routine is required for approximate evaluation of an integral using Simpson's rule on ten intervals, then, for it also to apply to any function supplied by the caller, the definition might be as follows:

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FUNCTION SIMPSN¶

FUNCTION SIMPSN (LO, HI, F)
REAL LO, HI, F
C
C THIS MAKES IT CLEAR THAT F IS AN ENTRY POINT THAT CAN
C BE INVOKED
C
EXTERNAL F
C INTERVAL SIZE
H = (HI - LO) / 10.0
C ADD UP VALUES OF FUNCTIONS
R = F (LO) + F (HI)
DO 10 I = 1, 9, 2
  R = R + 4 * F (LO + I * H)
10 CONTINUE
DO 20 I = 2, 9, 2
  R = R + 2 * F (LO + I * H)
20 CONTINUE
C FINAL CALCULATION
SIMPSN = R * H/3.0
RETURN
END

Note that it is not mandatory to have an EXTERNAL statement, in the function SIMPSN, but it is strongly recommended, so as to make the intention clear.

To evaluate the integral of one of your own functions (i.e. one that you have defined yourself), write:

FUNCTION OWN (X)
OWN = (1+X*X) ** (-1)
RETURN
END

and call the Simpson routine with:

VAL = SIMPSN (0.5, 1.0, OWN)

Note that in this case, i.e. defining the function OWN, the program unit containing the call to the function, SIMPSN, in the statement ''VAL=....'', requires a statement:

EXTERNAL OWN

If the invocation of SIMPSN is the only place OWN appears in this program unit, the EXTERNAL statement is required to inform the compiler that OWN is the name of an external procedure.

To evaluate the integral using an INTRINSIC function, for example, the trigonometric function SIN from 0 to 1 radians, the following invokes the function SIMPSN:

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INTRINSIC SIN¶

QUAD-SIMPSN(0.0,1.0,SIN)

This program unit must contain the INTRINSIC statement to use the INTRINSIC SIN function.

The argument passed to the function SIMPSN, is the specific name of the relevant INTRINSIC function, i.e. SIN for a REAL argument giving a REAL result. It is not the generic name SIN which gives access to the variants of SIN for REAL, DOUBLE or COMPLEX type arguments.

Beware that a symbolic name passed as a dummy argument must not occur in both an INTRINSIC and an EXTERNAL statement, within the same program unit. An INTRINSIC statement will cause the supplied functions to be used. An EXTERNAL statement will cause a user written function to be used. This could be a user defined version of a SIN function to be used instead of the supplied function; note that if this is done, the generic name SIN is no longer available in this program unit.

11.1.4 Asterisks as Dummy Arguments/Alternative Return Arguments¶

A dummy argument that is an asterisk may appear only in a dummy argument list of a SUBROUTINE statement or ENTRY statement in a subroutine subprogram.

An asterisk dummy argument can only be associated with an actual argument that is an alternate return argument in the relevant CALL statement, see Section 11.7 on page 248.

An alternative return actual argument must be a statement label preceded by an asterisk, as it appears within the argument list of a CALL statement, see Section 11.7.1 on page 248.

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11.2 INTRINSIC FUNCTIONS¶

INTRINSIC functions are supplied by FORTRAN and have special meanings. The specific names that identify the INTRINSIC functions, their generic names, function definitions, argument type, and result type appear in the table on page 225.

Note: An IMPLICIT statement does not change the type of an INTRINSIC function.

11.2.1 Specific Names and Generic Names¶

Generic names simplify the referencing of INTRINSIC functions since the same function may be used with more than one argument type.

If a generic name is used to reference an INTRINSIC function, the result type (except for those functions performing type conversion, nearest integer, and absolute value with a complex argument) is the same as the argument type.

Example:

For the cosine routine, whose generic name is COS, the specific names are COS, DCOS, and CCOS. If I, R, D, and C are variables of type INTEGER, REAL, DOUBLE PRECISION, and COMPLEX respectively, then:

COS (R) will invoke the routine called COS
COS (D) will invoke DCOS since it requests the double precision version
COS (C) will invoke the complex conversion CCOS

Note: In ND FORTRAN, COS(I) can be used to convert I to REAL, since COS is a specific name for the cosine function of REAL arguments.

Only a specific name may be used as an actual argument when the argument is an INTRINSIC function. (However, the names INT, IFIX, IDINT, FLOAT, SNGL, REAL, DBLE, CMPLX, ICHAR, CHAR, LGE, LGT, LLE, LLT, MAX, MAXO, AMAX1, DMAX1, AMAX0, MAX1, MIN, MIN0, AMIN1, DMIN1,

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AMINO, MNI1, IN1T, I2INT, DFLOAT, DCMPLX, IN1T, I2INIT,
I2DNINT, I2ABS, IMOD, I2MOD, I2SIGN, I2DIM, IMAX0,
IMINO, IAND, I2AND, IOR, I2OR, IEOR, I2EOR, NOT, I2NOT,
ISHFT, I2SHFT, IBIT, I2BIT, CLBIT, CLBIT, STBIT1,
I2STBIT1, GETBF, I2GETBF, PUTBF, I2PUTBF must not be used
as actual arguments.)

Otherwise, the actual arguments must agree in order,
number, and type with the specifications of the table
and may be any expression of the specified type. An
actual argument in an INTRINSIC function reference may
be any expression except a character expression of
unknown length (one involving concatenation of an
operand having its length given by an asterisk in
parentheses, unless the operand is the symbolic name of
a constant).

There is an exception to the above rule in ND FORTRAN.
If the name is a specific name, and no generic
selection is possible, then conversion of the actual
argument is attempted. It is for this reason that
COS(I) (see the previous example) is allowed. Other
examples are DCOS(R), when R converts to DOUBLE
PRECISION, and ALOG(I), when I converts to REAL.
LOG(I) is not allowed as LOG is not a specific name.

All INTRINSIC function references except CLBIT and
STBIT1 may have arrays as actual arguments, if the
INTRINSIC function reference is part of an array
expression. The INTRINSIC function will be evaluated
on an element by element basis.

Example:

REAL RES(10), ARG(10)
RES = SIN(ARG)

Another way of writing this assignment statement:

DO I = 1,10
RES(I) = SIN(ARG(I))
ENDDO

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11.2.2 Referencing an INTRINSIC Function¶

The reference to an INTRINSIC function uses its assigned name as an operand in an arithmetic or logical expression.

On the ND-100 with 48-bit floating-point hardware, short real variables in fact take 6 bytes. In the Table of INTRINSIC functions, REAL4 and COMPLEX8 are used for short real and complex variables on all machines. Consequently, any arguments shown in the table as short real variables, REAL4 or COMPLEX8, should be read as REAL6 and COMPLEX12 on an ND-100 with 48-bit floating-point hardware. Further, any INTRINSIC function returning a short real result, e.g. ALOG, will return a 6 byte real value on an ND-100 with 48-bit floating-point hardware.

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TABLE OF INTRINSIC FUNCTIONS¶

INTRINSIC Function	Definition	Number of Arguments	Generic Name	Specific Name	Type Argument
Type Conversion
Conversion to Integer INT(a) See Note 1	1	INT	-	Any arith	Default int.
			IFIX	Real*4	Integer*4
			IDINT	Real*8	Integer*4
			IINT	Any arith	Integer*4
			IZINT	Any arith	Integer*2
Conversion to Real See Note 2	1	REAL	REAL	Any arith	Real*4
			FLOAT	Integer*4	Real*4
			SNGL	Real*8	Real*4
Conversion to Double See Note 3	1	DBLE	DBLE	Any arith	Real*8
			DFLOAT	Integer*4	Real*8
Conversion to Complex See Note 4	1 or 2	CMPLX	CMPLX	Any arith	Complex*8
			DCMPLX	Any arith	Complex*16
Conversion to Integer See Note 5	1	-	ICHAR	Character*1	Default int.
Conversion to Character See Note 5	1	-	CHAR	Integer*2	Character*1

Truncation
INT(a) See Note 1	1	AINT	AINT	Real*4
			DINT	Real*8

Nearest Whole Number
INT(a+.5) if a>0 INT(a-.5) if a<0	1	ANINT	ANINT	Real*4
			DNINT	Real*8

Nearest Integer
INT(a+.5) if a>0 INT(a-.5) if a<0	1	NINT	-	Real*4
			ININT	Real*4
			IZININT	Real*4
			IDNINT	Real*8
			IZDNINT	Real*8

Absolute Value
	1	ABS	IABS
		IZABS	Integer*2
See Note 6		ABS	Real*4
		DABS	Real*8
		CABS	Complex*8
		CDABS	Complex*16

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INTRINSIC Function	Definition	Number of Arguments	Generic Name	Specific Name	Type of Argument	Type of Function
Remainder	( a_1 - INT(a_1/a_2)*a_2 ) See Note 1	2	MOD		Default int	Default int
				IMOD	Integer*4	Integer*4
				IZMOD	Integer*2	Integer*2
				AMOD	Real*4	Real*4
				DMOD	Real*8	Real*8
Transfer of Sign	(\pm a_1 ), based on sign of ( a_2 )	2	SIGN	ISIGN	Integer*4	Integer*4
				IZSIGN	Integer*2	Integer*2
				SIGN	Real*4	Real*4
				DSIGN	Real*8	Real*8
Positive Difference	( a_1 - a_2 ) if ( a_1 \ge a_2 ) 0 if ( a_1 < a_2 )	2	DIM	IDIM	Integer*4	Integer*4
				IZDIM	Integer*2	Integer*2
				DIM	Real*4	Real*4
				DDIM	Real*8	Real*8
Double Precision Multiply	DBLE(a_1)*DBLE(a_2)	2	DPROD	DPROD	Real*4	Real*8
Choosing Maximum Value	max(a_1, a_2, ...) See Note 9	≥ 2	MAX	MAX0	Default int	Default int
				IMAX0	Integer*4	Integer*4
				IZMAX0	Integer*2	Integer*2
				AMAX1	Real*4	Real*4
				DMAX1	Real*8	Real*8
				AMAX0	Default int	Real*4
				MAX1	Real*4	Default int
Choosing Minimum Value	min(a_1, a_2, ...) See Note 9	≥ 2	MIN	MIN0	Default int	Default int
				IMIN0	Integer*4	Integer*4
				IZMIN0	Integer*2	Integer*2
				AMIN1	Real*4	Real*4
				DMIN1	Real*8	Real*8
				AMIN0	Default int	Real*4
				MIN1	Real*4	Default int
Length	Length of Character Entity See Note 11	1	LEN	LEN	Character	Default int
Index of a Substring	Location of Substring ( a_2 ) in String ( a_1 ) See Note 10	2	INDEX	INDEX	Character	Default int
Imaginary Part of Complex Arguments	ai See Note 6	1	IMAG	AIMAG	Complex*8	Real*4
				DIMAG	Complex*16	Real*8

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INTRINSIC¶

Function	Definition	Number of Arguments	Generic Name	Specific Name	Type of Argument	Function Type
Conjugate of a Complex Argument	(ar, -ai)	1	CONJG	CONJG	Complex*8	Complex*8
				CDCONJG	Complex*16	Complex*16
Square Root	√a	1	SQRT	SQRT	Real*4	Real*4
	See Note 8			DSQRT	Real*8	Real*8
				CSQRT	Complex*8	Complex*8
				CDSQRT	Complex*16	Complex*16
Exponential	e**a	1	EXP	EXP	Real*4	Real*4
				DEXP	Real*8	Real*8
				CEXP	Complex*8	Complex*8
				CDEXP	Complex*16	Complex*16
Natural Logarithm	log (a)	1	LOG	ALOG	Real*4	Real*4
	See Note 8			DLOG	Real*8	Real*8
				CLOG	Complex*8	Complex*8
				CDLOG	Complex*16	Complex*16
Common Logarithm	log 10(a)	1	LOG10	ALOG10	Real*4	Real*4
				DLOG10	Real*8	Real*8
Logarithm (base 2)	log 2(a)	1	LOG2	ALOG2	Real*4	Real*4
				DLOG2	Real*8	Real*8
Sine	sin(a)	1	SIN	SIN	Real*4	Real*4
	See Notes 7, 8			DSIN	Real*8	Real*8
				CSIN	Complex*8	Complex*8
				CDSIN	Complex*16	Complex*16
Cosine	cos(a)	1	COS	COS	Real*4	Real*4
	See Notes 7, 8			DCOS	Real*8	Real*8
				CCOS	Complex*8	Complex*8
				CDCOS	Complex*16	Complex*16
Tangent	tan(a)	1	TAN	TAN	Real*4	Real*4
	See Note 7			DTAN	Real*8	Real*8
Arcsine	arcsine(a)	1	ASIN	ASIN	Real*4	Real*4
	See Note 7			DASIN	Real*8	Real*8
Arccosine	arccosine(a)	1	ACOS	ACOS	Real*4	Real*4
	See Note 7			DACOS	Real*8	Real*8

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INTRINSIC Function	Definition	Number of Arguments	Generic Name	Specific Name	Type Argument	Type of Function
Arctangent	arctan(a)	1	ATAN	ATAN	Real*4	Real*4
				DATAN	Real*8	Real*8
	arctan(a₁, a₂) See Note 7	2	ATAN2	ATAN2	Real*4	Real*4
				DATAN2	Real*8	Real*8
Hyperbolic Sine	sinh(a)	1	SINH	SINH	Real*4	Real*4
				DSINH	Real*8	Real*8
Hyperbolic Cosine	cosh(a)	1	COSH	COSH	Real*4	Real*4
				DCOSH	Real*8	Real*8
Hyperbolic Tangent	tanh(a)	1	TANH	TANH	Real*4	Real*4
				DTANH	Real*8	Real*8
Lexically Greater Than or Equal	a₁ ≥ a₂ See Note 12	2	-	LGE	Character	Default log
Lexically Greater than	a₁ > a₂ See Note 12	2	-	LGT	Character	Default log
Lexically Less Than or Equal	a₁ ≤ a₂ See Note 12	2	-	LLE	Character	Default log
Lexically Less than	a₁ < a₂ See Note 12	2	-	LLT	Character	Default log
AND	arg 1.AND.arg 2 See Note 13	2	IAND	IAND	Integer*4	Integer*4
				I2AND	Integer*2	Integer*2
OR	arg 1.OR.arg 2 See Note 13	2	IOR	IOR	Integer*4	Integer*4
				I2OR	Integer*2	Integer*2
Exclusive OR	arg 1.NEQV.arg 2 See Note 13	2	IEOR	IEOR	Integer*4	Integer*4
				I2EOR	Integer*2	Integer*2
NOT	logical complement	1	NOT	NOT	Integer*4	Integer*4
				I2NOT	Integer*2	Integer*2
Bit Shifting	shifts value left or right See Note 14	2	ISHFT	ISHFT	Integer*4	Integer*4
				I2SHFT	Integer*2	Integer*2

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INTRINSIC Function	Definition	Number of Arguments	Generic Name	Specific Name	Type Argument	Type of Function
Bit Extract	0 if bit arg 2 of arg 1 is 0, else -1 See Note 15	2	IBIT	IBIT	Integer*4	Integer*4
				I2BIT	Integer*2	Integer*2
Clear bit	sets bit arg 2 of arg 1 to 0 See Note 15	2	CLBIT	CLBIT	Integer*4
				I2CLBIT	Integer*2
Set bit	sets bit arg 2 of arg 1 to 1 See Note 15	2	STBIT	STBIT	Integer*4
				I2STBIT	Integer*2
Get bit field	See Notes 15,16	3	GETBF	GETBF	Integer*4	Integer*4
				I2GETBF	Integer*2	Integer*2
Set bit field	See Notes 15,16	4	PUTFBF	PUTFBF	Integer*4	Integer*4
				I2PUTBF	Integer*2	Integer*2

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Notes on Table of Intrinsic Functions¶

(1)¶

For a a of type integer, INT (a) = a. For a a of type real or double precision, there are two cases:

if |a| < 1, INT(a)=0
if |a| ≥ 1, INT(a)

is the integer whose magnitude is the largest integer that does not exceed the magnitude of a and whose sign is the same as the sign of a. For example:

INT (-3.7) = -3

For a of type complex, INT (a) is the value obtained by applying the above rule to the real part of a.

For a a of type real, IFIX (a) is the same as INT (a).

The result of INT is the default integer type for this compilation. (See "DEFAULT command", Section 14.24.1 on page 293).

To convert to INTEGER*2, use I2INT, and to INTEGER*4, use IINT.

(2)¶

For a a of type real, REAL (a) is a. For a of type integer or double precision, a is converted to type REAL. If significant bits are lost, the result is truncated. If a has type complex, REAL (a) is the real part of a.

If a is of type integer, FLOAT (a) is the same as REAL (a).

(3)¶

For a a of type double precision, DBLE (a) = a. For a type of integer or real, the result is converted to double precision so that no significant bits can be lost in conversion.

(4)¶

CMPLX may have one or two arguments. If there is one argument, it may be of type integer, real, double precision, or complex. If there are two arguments, they may be of type integer, real, or double precision, but must both be of the same type.

If a has type complex, CMPLX (a) = a. For a of type integer, real, or double precision, CMPLX (a) is the complex value whose real part is REAL (a) and whose

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imaginary part is zero.

CMPLX (a₁, a₂) is the complex value whose real part is REAL (a₁) and whose imaginary part is REAL (a₂). DCMPLX acts analogously with a result of DOUBLE COMPLEX.

ICHAR Function¶

(5) ICHAR provides a means of determining the position of a character in the collating sequence, which for ND machines is the ASCII sequence. There are 128 values in this sequence. For example, the letter A is number 65, and the first (NULL) is 0 (zero).

The argument a is a character of length 1.

In ND FORTRAN, if the length is greater than 1, the first character is used. No check is made to see if the value is more than 127; hence care should be taken if this is used on values where the parity bit has not been cleared.

For any characters c₁ and c₂, (c₁ .LE. c₂) is true if and only if ICHAR (c₁ ) .LE. ICHAR (c₂ ) is true, and (c₁ .EQ. c₂) is true if and only if (ICHAR (c₁) .EQ. ICHAR (c₂)) is true.

The result is of default integer type (see Section 14.24.1, on page 293).

CHAR Function¶

CHAR (i) returns the character in the ith position of the collating sequence. The value is of type character of length one. i must be an integer expression whose value must be in the range 0<i<128. In ND FORTRAN, no check is made that the integer is in the restricted range; hence care must be taken if parity bits are being manipulated.

Function	Condition
ICHAR (CHAR (i))	`i` for 0<i<128
CHAR (ICHAR (c))	`c` for any character `c`.

Complex Values¶

(6) A complex value is expressed as an ordered pair of reals, (ar, ai), where ar is the real part and ai is the imaginary part.

Angles¶

(7) All angles are expressed in radians.

Complex Function Results¶

(8) The result of a function of type complex is the

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principal value.

(See the restrictions which follow these notes, on page 234.)

Notes¶

(9) All arguments in an INTRINSIC function reference must be of the same type.

In ND FORTRAN, arguments are automatically converted to the highest order data type, see Section 5.1.1, on page 82, according to the normal rules of operand matching for arithmetic operators.

(10) INDEX (a₁, a₂) returns an integer value indicating the starting position within the character string a₁ of a substring identical to string a₂. If a₂ occurs more than once in a₁, the starting position of the first occurrence is returned.

If a₂ does not occur in a₁, the value zero is returned. Note that zero is returned if LEN(a₁)<LEN(a₂). Zero is also returned if the second argument is a null string.

(11) The value of the argument of the LEN function need not be defined at the time the function reference is executed.

(12)
LGE (a₁, a₂) returns the value .TRUE. if a₁ = a₂ or if a₁ follows a₂ in the collating sequence described in American National Standard Code for Information Interchange, ANSI X3.4-1977 (ASCII). Otherwise, it returns the value .FALSE..

LGT (a₁, a₂) returns the value .TRUE. if a₁ follows a₂ in the collating sequence described in ANSI X3.4-1977 (ASCII), and otherwise returns the value .FALSE..

LLE (a₁, a₂) returns the value .TRUE. if a₁ = a₂ or if a₁ precedes a₂ in the collating sequence in ANSI X3.4-1977 (ASCII), and otherwise returns the value .FALSE..

LLT (a₁, a₂) returns the value .TRUE. if a₁ precedes a₂ in the collating sequence described in ANSI X3.4-1977 (ASCII), and otherwise returns the value .FALSE..

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If the operands for LGE, LGT, LLE, and LLT are of unequal length, the shorter operand is considered as if it were extended on the right with blanks to match the length of the longer operand.

In ND FORTRAN, the comparison is done character by character, treating each one as an unsigned 8-bit integer.

(13) The logical operators are defined for integers in ND FORTRAN by applying the operator to each bit position of the arguments independently. These functions have identical results to the logical operators, see Section 5.4 on page 92.

(14) ISHFT (arg 1, arg 2) shifts the bits in arg 1 by arg 2 positions. If arg 2 is positive, the shift is to the left (i.e., towards the highest order bit). If arg 1 is negative, the shift is to the right. In both cases, zeros are moved into the vacated bit positions.

For arg 1 of type INTEGER2, -16 ≤ arg 2 ≤ 16
and for arg 1 of type INTEGER4, -32 ≤ arg 2 ≤ 32.

(15) Bits are counted from the rightmost (least significant) bit, which is labeled 0. The leftmost bit is number 15 for INTEGER2, and 31 for INTEGER4.

The entry points CLBIT, I2CLBIT, STBIT, I2STBIT are subroutine entries. They may only be invoked by a CALL statement, and they return no value.

(16) GETBF and PUTBF may only be used in ND-500.

GETBF: The first argument specifies the operand where the bit field is taken from. The second argument defines the bit number where the bit field starts. The third argument specifies the number of bits in the bit field.

DEST = GETBF (SOURCE1, STARTB, BTWIDTH)

PUTBF: The second and third arguments specify the bit field as in GETBF. The fourth argument holds the bits that are going to be stored in the first.

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argument's bit map.

DEST = PUTBF (SOURCE1, STARTB, BTWIDTH, SOURCE2)

RESTRICTIONS ON RANGE OF ARGUMENTS AND RESULTS¶

Restrictions on the range of arguments and results for INTRINSIC functions when referenced by their specific names are as follows:

Remainder: The result for MOD, AMOD, and DMOD is undefined when the value of the second argument is zero.
Transfer of Sign: If the value of the first argument of ISIGN, SIGN, or DSIGN is zero, the result is zero, which is neither positive nor negative.
Square Root: The value of the argument of SQRT and DSQRT must be greater than or equal to zero. The result of CSQRT is the principal value with the real part greater than or equal to zero. When the real part of the result is zero, the imaginary part is greater than or equal to zero.
Logarithms: The value of the argument of ALOG, DLOG, ALOG10, DLOG10, ALOG2 and DLOG2 must be greater than zero. The value of the argument of CLOG must not be (0., 0.). The range of the imaginary part of the result of CLOG is:

-pi < imaginary part ≤ pi.

The imaginary part of the result is pi only when the real part of the argument is less than zero and the imaginary part of the argument is zero.
Trigonometric functions: The values of the complex circular functions are defined as follows:

If z is complex and z = x+iy, where x, y are real, then:

Function Definition

sin (z) sin (x) cosh (y) + i cos (x) sinh (y)

cos (z) cos (x) cosh (y) - i sin (x) sinh (y)

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The following INTRINSIC functions are ND FORTRAN extensions:

double complex functions:¶

CDSIN, CDCOS, CDEXP, CDLOG, CDSQRT, CDABS, CDCONJG, DCMPLX, DIMAG

log to base 2:¶

LOG2, ALOG2, DLOG2

integer*2 functions:¶

I2MIN0, I2MAX0, I2MOD, I2ABS, I2SIGN, I2DIM

integer*4 functions:¶

IMIN0, IMAX0, IMOD

conversions:¶

I2NINT, TINT, I2NINT, ININT, I2DNINT, DFLOAT

generic names:¶

IMAG

bit operations:¶

IAND, I2AND, IOR, I2OR, IEOR, I2EOR, ISHFT, I2SHFT, NOT, I2NOT, IBIT, I2BIT, CLBIT, I2CLBIT, STBIT, I2STBIT

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11.3 STATEMENT FUNCTIONS¶

A statement function is a procedure specified by a single statement that is similar in form to an arithmetic, logical, or character assignment statement. This statement is nonexecutable and not part of the normal execution sequence. However, these definitions must follow all declaratives and precede executable statements.

The general form of a statement function is:

symb ([arg1, arg2, ...])=e

where


`symb`	is the symbolic name of the statement function
`arg`	is a dummy argument, and
`e`	is an expression.

The relationship between symb and e must conform to the standard assignment rules, see Chapter 7 on page 115.

Example:

The Euclidean distance between points (X1, Y1) and (X2, Y2) could be represented by:

DIST (X1, Y1, X2, Y2) = SQRT ((X1-X2)**2+(Y1-Y2)**2)

To use this function to evaluate the distance between the i-th and j-th points represented by arrays A (for the X's) and B (for the Y's), the following could be written:

DIST (A (I), B (I), A (J), B (J))

It is not necessary to restrict the operands in the expression to the statement function's dummy arguments. As an example, suppose the values A, B and C are defined in a COMMON block, then the evaluation of a quadratic expression with these coefficients could be defined as:

QUADR (X) = (A*X+B) * X+C

The dummy argument names have the scope of the statement function only.

A statement function produces only one value, that is, the result of the expression it contains.

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The actual arguments must agree in order, number, and type with the corresponding dummy arguments. An actual argument may be any expression except a character expression involving concatenation of an operand whose length specification is an asterisk in parentheses, unless the operand is the symbolic name of a constant.

In ND FORTRAN, however, conversion will be carried out, where possible, if the actual and dummy arguments are not of the same type.

11.3.1 Statement Function Restrictions¶

A statement function may be referenced only in the program unit that contains the statement function statement.

A statement function statement must not reference another statement function which appears in subsequent lines of the program unit.

The symbolic name identifying the statement function must not be used as a symbolic name in any specification statement (except in a Type statement for specifying the type of function) or as the name of a common block in the same program unit.

An external function reference in the expression e must not cause a dummy argument of the associated statement function to become undefined or redefined.

The symbolic name of a statement function is a local name, see Section 1.3 on page 6, and must not be the same as the name of any other entity in the program unit except the name of a common block.

The symbolic name of a statement function may not be an actual argument. It must not appear in an EXTERNAL statement.

In ND FORTRAN, if an actual argument differs in type from the corresponding dummy argument, then the actual arguments are converted to the type of the dummy argument.

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A statement function statement in a function subprogram must not contain a reference to the name of the function subprogram or an entry name in the function subprogram.

11.3.2 Referencing a Statement Function¶

A statement function is referenced by using its function reference in an expression.

Note that if a statement function has no dummy arguments, its definition and reference must still include empty argument lists.

For example:

LOGICAL CONSEC
CONSEC () = ABS (X-Y) .EQ. 1
IF (CONSEC ()) THEN
ENDIF

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11.4 EXTERNAL FUNCTIONS¶

External functions are both external procedures and function subprograms. They consist of a FUNCTION statement followed by a sequence of FORTRAN statements which define desired operations. They may also contain one or more RETURN statements and must be terminated by an END statement.

The form of a FUNCTION statement is:

| [type] FUNCTION name [([ arg1 [,arg2] ...])] |

where

type is either INTEGER, REAL, DOUBLE PRECISION, COMPLEX, LOGICAL, NUMERIC (fw,sc) or CHARACTER [I] where I is the length of the result. I may have any of the forms of those allowed in the CHARACTER statement, except that an integer constant expression must not include the symbolic name of a constant. The default for I is one.
(Note: type may be specified in a Type statement instead. The normal implicit rules apply if neither form is used.)

Name is the symbolic name of the function subprogram in which the FUNCTION statement appears; it is an external function name.

arg is a dummy argument.

The symbolic name of the function subprogram must appear as a variable name in this subprogram. Its value on execution of a RETURN or END statement in the subprogram is the value of the function.

An external function may also modify one or more of its dummy arguments.

11.4.1 Actual Arguments for an External Function¶

Actual arguments in the function reference must agree in order, number and type with the corresponding dummy arguments in the referenced function. An exception to

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this rule is when a subroutine name appears as an actual argument, because subroutine names do not have a type.

Actual arguments may be:

An expression. (Except a character expression of unknown length, e.g. one involving concatenation of an operand whose length is given by an asterisk in parentheses, unless the operand is the symbolic name of a constant.)

An array name

An intrinsic function name

An external procedure name

A dummy procedure name (see Section 11.1.3, on page 219).

Note that an actual argument in a function reference may be a dummy argument in a dummy argument list within the same subprogram.

11.4.2 Function Subprogram Restrictions¶

A FUNCTION statement should only appear as the first statement of a function subprogram. A function subprogram may contain any other statement except a BLOCK DATA, SUBROUTINE, or PROGRAM statement.

The symbolic name of an external function is a global name and cannot, therefore, be the same as any other global name.

In ND FORTRAN however, COMMON blocks can have the same names as external procedures.

A function specified in a subprogram may be referenced in any other procedure subprogram or in the main program. A function subprogram must not reference itself, either directly or indirectly.

In ND FORTRAN, if the REENTRANT-MODE ON command on ND-100 or the FIXED-DATA-AREA OFF command on ND-500 is chosen, recursive calls are allowed for external procedures. Note that recursion is never allowed for

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Statement Functions¶

If a function has no dummy arguments, its FUNCTION statement may omit the argument list. But its reference may not omit the list.

For example:

CHARACTER*1 FUNCTION NEXTCH
READ (IN, '(A1)') NEXTCH
RETURN
END

then the form of the invocation must be, as in this example:

IF (NEXTCH().EQ.'+') GO TO 10

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11.5 SUBROUTINES¶

A subroutine is an external procedure which is identified by a SUBROUTINE statement.

The SUBROUTINE statement must be the first statement of the subroutine subprogram and it has the form:

| SUBROUTINE name [([arg1 [,arg2] ...])] |

where

name is the symbolic name of the subroutine subprogram in which the SUBROUTINE statement appears
arg1... is a dummy argument list consisting of variable names, array names, or procedure names. A dummy argument can also be an asterisk, see page 221.

Note: If there are no dummy arguments, either of the forms, name or name(), can be used in the SUBROUTINE statement. Likewise a subroutine can be referenced, according to the form in which it was specified, by CALL name or CALL name().

11.5.1 Subroutine Reference¶

A subroutine is referenced by the CALL statement which has the form:

| CALL name [([arg1 [,arg2] ...])] |

where

name is the symbolic name of the subroutine subprogram
arg1... is an optional list of actual arguments.

A subroutine specified in a subprogram may be referenced within any other procedure subprogram or within the main program. A subroutine subprogram must not reference itself, either directly or indirectly.

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In ND FORTRAN, if the REENTRANT-MODE ON command on an ND-100, or the FIXED-DATA-AREA OFF command on an ND-500 are chosen, a subroutine subprogram may reference itself, either directly or indirectly.

The use of a subroutine name or an alternate return specifier (see the RETURN statement on page 248, in this chapter) as an actual argument is an exception to the rule requiring agreement of type between dummy and actual arguments.

Note that an actual argument may be a dummy argument name that appears in a dummy argument list within the subprogram containing the reference. An asterisk dummy argument must not be used as an actual argument in a subprogram reference.

11.5.2 Subroutine Subprogram Restrictions¶

A subroutine subprogram may contain any other statement except a BLOCK DATA, FUNCTION, or PROGRAM statement.

The symbolic name is a global name, and cannot, therefore, be the same as any other global name. See the examples earlier in this chapter.

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11.6 THE ENTRY STATEMENT¶

The ENTRY statement enables additional entry points into an external subprogram to be specified. It may appear anywhere within a function or subroutine subprogram. However, it may not appear between a block IF and its corresponding ENDIF statement, or between a DO statement and the terminal statement of its DO-loop.

An ENTRY statement is nonexecutable. It has the form:

| ENTRY name [([arg1 [,arg2]...])] |

where

name is the symbolic name of an entry in a function or subroutine program and is known as an entry name.
arg1... is an optional list of dummy arguments which may be variable names, array names, dummy procedure names, or an asterisk. This last argument type is permitted only in a subroutine subprogram. A dummy procedure is defined in Section 11.1.3, on page 219.

Note that if there are no dummy arguments, either name or name() can be used in the ENTRY statement. A function specified by either form must be referenced by name(). A subroutine specified by either form can be referenced by a CALL statement, using either CALL name or CALL name().

The symbolic entry name may appear in a Type statement.

Execution of the external procedure begins with the first executable statement following the relevant ENTRY statement.

An entry name can be referenced in any program unit except the one containing the entry name in an ENTRY statement.

The order, number, type, and names of the dummy arguments of the ENTRY statement may be different from the order, number, type, and names of the dummy arguments in the FUNCTION or SUBROUTINE statements and other ENTRY statements in the same subprogram. However, each reference to a function or subroutine must use an actual argument list that agrees in order, number, and type with the corresponding dummy argument list of the FUNCTION, SUBROUTINE, or ENTRY statement.

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subroutine name or alternate return specifier (see Section 11.7, on page 248) as an actual argument is an exception to the rule requiring agreement of type.

For any particular subroutine call or function invocation at one of its entry points, only those dummy arguments specified at the point of entry can be assumed to have a value during this call/invocation.

For example:

SUBROUTINE SUB
.
.
.
ENTRY INIT (A,B,C)
.
.
.
ENTRY LOOKUP (A,X)
.
.
.
ENTRY STORE (Y,A)
.
.
.
END

If the routine was entered at entry INIT, the dummy arguments A, B and C have values. But if the entry is via LOOKUP, then only A and X, but not B nor C, will have values. Any access to B and C will give unpredictable results.

Note that in entry STORE, the dummy argument A is defined at a different position in the list.

Within a function subprogram, all variables whose names are also the names of entries are associated with each other and with the variable whose name is also the name of the function subprogram. Therefore, any such variable that becomes defined, causes all associated variables of the same type to become defined and all associated variables of different types to become undefined.

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11.6.1 ENTRY Statement Restrictions¶

An entry name cannot be used as a dummy argument in a FUNCTION, SUBROUTINE or ENTRY statement within the same subprogram in which it appears as an entry name. It must not appear in an EXTERNAL statement.

In ND FORTRAN, if the REENTRANT-MODE ON command on an ND-100, or the FIXED-DATA-AREA OFF command on an ND-500 is chosen, recursion is allowed.

In a function subprogram, a variable having the same name as the entry name, must not appear in any statement preceding the ENTRY statement associated with the entry name (except in a Type statement).

In a subprogram, a name used as a dummy argument in an ENTRY statement, must not appear in an executable statement preceding that ENTRY statement except in a FUNCTION, SUBROUTINE or ENTRY statement. Likewise, it must not appear in the expression of a statement function statement, unless the name is also a dummy argument of the statement function, or appears in a FUNCTION or SUBROUTINE statement, or appears in an ENTRY statement preceding the statement function statement.

If a dummy argument does appear in an executable statement, such execution is only permitted if, during the execution of a reference to the function or subroutine, the dummy argument is in the list of dummy arguments of the procedure name referenced.

For example, if two functions have very similar algorithms barring some initialization code, then they can be written in one external function with a second entry point. The following function with two entry points searches an array of integers, IA, for either an odd or even value, depending on the entry point.

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FUNCTION IODD (IA, N)
  IODD = 0
  M = 1
  GO TO 10

ENTRY IEVEN (IA, N)
  IEVEN = 0
  M = 0

C COMMON CODE STARTS HERE
10 CONTINUE
  DO 20 K=1, N
    IF (MOD (IA (K), 2).EQ.M) THEN
      IF (M.EQ.1) IODD=K
      IF (M.EQ.0) IEVEN = K
      RETURN
    ENDIF
20 CONTINUE
END

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11.7 THE RETURN STATEMENT¶

The RETURN statement causes control to be returned from a subprogram to the calling program unit. The form of a RETURN statement in a function subprogram is:

RETURN

The form of a RETURN statement in a subroutine subprogram is:

RETURN [e]

where

e is an integer expression.

During execution, the value of the expression e will select one of the alternative RETURN actual arguments specified in the relevant CALL statement, see the next section.

11.7.1 Execution of a RETURN Statement¶

Execution of a RETURN statement in the first of the above forms causes control to be returned to the statement of the calling program following the statement that calls the subprogram.

Execution of a RETURN statement in the second form given above also returns control to the referencing program unit and it completes the execution of the CALL statement whether e is specified or not.

However, if:

1 ≤ e ≤ n

where

n is the number of asterisks in the SUBROUTINE or subroutine ENTRY statement, then e identifies the e-th asterisk in the dummy argument list. Control will now be returned to the e-th statement label in the argument

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list of the calling statement. This is known as the alternate return specifier.

Example:¶

The following subprogram checks a number for validity (in this case it tests for integers from 1 to 10) and takes an alternate return if it fails.

SUBROUTINE VALCHK (X,*,*)
  IF (X.LT.1.OR.X.GT.10) RETURN 1
  IF (INT(X).NE.X) RETURN 2
  END

and it can be used as follows:

CALL VALCHK (TYPE, * 90, * 91)
C OKAY IN NORMAL CONTINUATION
......
90 STOP 'OUT OF BOUNDS'
91 STOP 'NOT AN INTEGER'

Execution of a RETURN (or END) statement causes all entities within the subprogram in which it occurs to become undefined except for the following:

Entities specified by SAVE statements.
Entities in blank common.

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CHAPTER 12¶

MAIN PROGRAM¶

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MAIN PROGRAM¶

A main program is a program unit which does not have a FUNCTION, SUBROUTINE, or BLOCK DATA statement as its first statement.

An executable program must have exactly one main program in it and the first executable statement of the main program is also the first executable statement of the executable program which contains it.

12.1 THE PROGRAM STATEMENT¶

The form of a PROGRAM statement is:

| PROGRAM pgm |

where

pgm is the symbolic name of the main program in which the PROGRAM statement appears.

A PROGRAM statement is not mandatory, but if it appears, it must be the first statement of the main program.

In ND FORTRAN, if the PROGRAM statement is omitted, the name £MAIN is generated.

Since the symbolic name, pgm, is global, it must not be used as any local name within the main program, neither may it be the name of an external procedure, BLOCK DATA subprogram, or COMMON block of the executable program in which it appears.

A main program may not be referenced from a subprogram or from itself.

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In ND FORTRAN, a program which is to be executed as an RT-program can be given a priority at compile-time by the following form of the statement:

PROGRAM pgm, priority

priority is an unsigned integer constant which must be less than 256. This is the default priority assigned by the RT loader to this program. The priority is ignored in backgrounds operation.

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Chapter 13¶

Block Data Subprogram¶

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BLOCK DATA SUBPROGRAM¶

BLOCK DATA subprograms are used to provide initial values for variables and arrays in named common blocks. They are nonexecutable and more than one may appear in an executable program. The first statement of a BLOCK DATA subprogram is a BLOCK DATA statement which has the form:

BLOCK DATA [sub]

where

sub is the symbolic name of the BLOCK DATA subprogram in which the statement appears.

The optional name sub is global and cannot therefore be the same name as that of an external procedure, main program, COMMON block, or other BLOCK DATA subprogram in the same executable procedure. Neither can it be the same as any local name in the subprogram.

Initial values may be entered into more than one labelled COMMON block in a single subprogram of this type.

13.1 BLOCK DATA SUBPROGRAM RESTRICTIONS¶

The only other statements that can appear in a BLOCK DATA subprogram are IMPLICIT, PARAMETER, DIMENSION, COMMON, SAVE, EQUIVALENCE, DATA, END and Type statements. Comment lines are permitted.

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Chapter 23¶

For the output to become correct when the CSUBR program is changed, it is necessary to alter all constants in the program and recompile the program. This can be avoided:

By using variables instead of constants, the program becomes entirely independent of the possible changes in the CSUBR program. The values assigned to these variables must be part of the manual documentation for the subroutine.

Table 23-1: The CALL Statement - Interface Summary and Example

Argument	Value
A	1.0
I	1

The SAMPLE program shows how to use this concept.

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Chapter 14¶

Compiler Commands¶

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14.1 COMPILER INVOCATION AND TERMINATION¶

The compiler is invoked from SINTRAN by the command:

| @ND FORTRAN-500 |

or

| @FORTRAN-100 |

The compiler responds with a notification of the version in use. It then prompts by writing on the terminal:

| FTN: |

When these characters appear with the cursor at the next position, the compiler is in 'command mode', i.e., awaiting commands.

The command:

| EXIT |

will return control to SINTRAN after all source, list, and object files have been closed.

It is ignored if found in the source text.

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14.2 COMPILER COMMAND SYNTAX¶

The command names can be abbreviated. Only the number of letters needed to make the command name unique need be typed, but more may be given if required (e.g., for readability or documentation). The parameters for a command can be written on the same line as the command name but separated from it by one or more blanks. The parameters are separated from each other by one or more blanks and at most one comma. Alternatively, if parameters are expected but not given, the compiler will prompt for them in turn.

Most commands may also be written as part of the source program, but in this case all parameters must be on the same line as the command name, and the command name must be preceded by a $ symbol. Blanks may appear before the $ and between the $ and the command name. Such commands can only be written between statements. They cannot occur in the middle of a statement, or between successive continuation lines of a statement.

In the description of the commands in this manual, those commands which can only be placed in the source program are written with the preceding $.

A number of commands have just one parameter, which is either ON or OFF. For all such parameters, if the parameter is omitted, ON is assumed; and if it is not recognized (for example, due to mistyping) then OFF is assumed.

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14.3 THE HELP COMMAND¶

The HELP command will list the available compiler commands and information about the possible values of their parameters.

The command is written:

| HELP [name] |

where

name may be the name of any command, or an abbreviation.

If an abbreviation is used, all commands beginning with that abbreviation will be listed.

If no name value is entered, all commands will be listed.

Each command will be listed with its required parameters, and an indication of the possible parameter values. The current values of parameters will also be shown, where relevant.

14.4 COMMENTS¶

Comments may be included with the commands, and has the following form:

| CC comment |

Whatever follows the command name CC on the same line, is treated as a comment and ignored by the compiler. This is primarily useful for inserting comments in a batch or mode job.

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14.5 COMPILATION OF SOURCE PROGRAMS¶

14.5.1 The COMPILE Command, Preparation of Relocatable Code¶

The most important command is the COMPILE command which determines the program to be compiled and where the output is to be placed. This is written as:

COMPILE source [list][object]

where

source is the name of the file, or unit number, containing the FORTRAN program to be compiled. This parameter cannot be omitted. If TERMINAL or unit 1 is specified, input is accepted from the terminal, line by line, until $EOF command is encountered in the input stream. In this case, the compiler returns to command mode. If a name is specified, it must obey the usual SINTRAN syntactic form and conventions. The first default type is SYMB and the second default type is FORT.

list is the name of the file or unit number to which the source listing will be printed by the compiler. The format of the output will be suitable for printing and will contain the ASCII LF, CR, and FF characters for carriage control. Parity will be set on this file.

If 0 is specified, the listing is suppressed.

If TERMINAL or 1 is specified, the output will appear on the terminal. If this parameter is omitted, the output will be written as a continuation of the list file of the immediately previous COMPILE command, or, if none, the listing will be suppressed.

The first default type is SYMB and the second default type is LIST.

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object is the name of the file, or unit number which will contain the compiled relocatable version of the program. This is the input to the loader when creating a program. See the ND Relocating Loader manual ND-60.066 for details.

If 0 is specified, no relocatable code is generated, but a complete compilation takes place, thus giving any diagnostic messages that may occur.

If the object file is omitted, the output is a continuation of the last object file, if any, or 0 is assumed and the output is suppressed.

If a unit number is given, it must be octal without any trailing B.

The default type of the object file is BRF on the ND-100, NRF on the ND-500.

After the COMPILE command is completed, the prompt FTN: reappears on the terminal.

Any diagnostic messages generated by the compiler are listed at the terminal, and also on the list file, if different. The messages may be warnings or errors. If any errors are found before the END statement is encountered, the code generation will not proceed, and the relocatable output will be suppressed.

The end of the source text is either the end-of-file or a $EOF encountered in the source file.

On the source listing, the numbers printed on the far left are line numbers, which number sequentially all the lines in the program units within a single listing. Each listing starts with line 1.

Error messages, the symbolic debugger and the cross-reference listing refer to statement numbers. Each statement is given a number equal to the line number on which the first character of the statement is found. Thus, if several statements are written on one line, they all have the same statement number. If a statement consists of more than one line, the statement numbers will not be consecutive. It is hoped that this mechanism will help during editing because the error reports refer to a line number close to the error. See also the next section.

The compile command is ignored if found in the source file.

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14.5.2 Including Text From Other Source-Files¶

Other files can be incorporated in the source program at the points indicated by the command:

$INCLUDE filename

where

| filename | is the name of the file or unit number to be read. The parameter cannot be omitted; the default file type is SYMB. |

This command cannot be used in command mode.

The reading of the source program by the compiler is switched to the named file and continues until either the end-of-file is found, or a $EOF command is encountered. The file is then closed and the text following the $INCLUDE command is read. The named file may itself contain further $INCLUDE commands, but no more than five incomplete $INCLUDEs may be in existence at any one time.

For example, in a suite of subroutines which all share a COMMON block, the definition of that block could be held on a file called COMDEF:SYMB. Then by writing:

$INCLUDE COMDEF

at the appropriate point in each subroutine, the definition is brought into the source file. Thus only one copy of the COMMON block definition is kept, and all subroutines have identical declarations of it.

When a file is included, two numbers are printed on the source listing. The first is the statement number, which is the one which the symbolic debugger uses. The second number is the line number in the file which contains the line. Error messages refer to both numbers. If the second number is surrounded by slashes, then the line is part of an included file. If it is in parentheses, then it is in the original source file.

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14.5.3 End of File¶

The command:

$EOF

signifies that the reading of the current file is complete. Reading continues at the next outer INCLUDE level.

It is ignored in command mode.

14.5.4 Preparation of Executable Programs and Loading¶

In FORTRAN-100, an executable program may be prepared and output to a file, by using the command:

PROG-FILE filename

where

filename is the name of a file to receive the executable program.

The default file type is PROG.

If the COMPILE command is used subsequent to the PROG-FILE command, then the compiler will generate the executable program directly on to this file. The COMPILE command will still generate an object file if it is specified, in addition to the PROG file.

PROG-FILE commands will be ignored if they are placed in the source file.

The executable program is completed automatically, by loading the FORTRAN library (1 or 2 bank, depending on the setting of the SEPARATE-DATA option), when the EXIT command is given.

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The PROG-FILE command can be issued at most once during any invocation of the compiler.

In FORTRAN-500 an executable program may be prepared and output to a file by the command:

SEGMENT-FILE [filename]

If no filename is specified, two temporary files are used and deleted when exiting from the compiler. If filename (with no type) is specified, two files are used:

filename:SWPO
filename:SWO1

If the COMPILER command is used subsequent to the SEGMENT-FILE command, the compiler will generate an executable program directly on to the file specified in the SEGMENT-FILE command. The compiler will still generate an object-file if it is specified. The SEGMENT-FILE command will be ignored if it is placed in the source-file. The executable program is completed automatically when the RUN command is given.

To complete the executable program, libraries or other object files may be added by using the command:

LOAD filename [,filename] . . .

where filename is the name of an object file or library.

The default type of the file loaded will be BRF on the ND-100 and NRL on the ND-500.

LOAD commands will be ignored if they are placed in the source file.

Any error messages which appear while the LOAD command is being executed can be found in the ND Relocating Loader Manual (ND-60.065) and in the ND-500 LOADER/MONITOR Manual (ND-60.136).

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To define entry points in the "built-in" loader table we can use:

| DEFINE , , |

If a ? appears instead of entry-name, then a map of undefined entries will be displayed on the terminal. If the entry-name is omitted, then a map of defined entries will be displayed.

value gives the load address in octal.
mode indicates either a program area (P) or data area (D).

In FORTRAN-100 it is possible to set the current load address by using * instead of entry-name. Then the value-parameter will give the current load-address.

The command:

| LINK-SEGMENT |

is available in FORTRAN-500. The specified segment will be linked to the program in the files specified in the SEGMENT-FILE command.

The command:

| RUN |

will load the FORTRAN library and start execution of the program.

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14.5.5 Combined Compile and Execution¶

A simple to use Compile and Execute facility is available if the compiler is invoked on ND-100 by the command:

@FORTRAN-100 source-file

and on ND-500 by the command:

@FORTRAN-500 source-file

The compiler will generate an executable program, and begin execution, provided that the program has compiled successfully.

When using FORTRAN-100, the executable program will be stored in a file with the same name as the source-file, but with type PROG. If the PROG file does not exist, it will be created.

When using FORTRAN-500, the executable program will be stored in a temporary file which will be deleted after execution.

It is possible to give commands to the compiler when invoked in this way. Each command must start with $ and end with /.

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The general form of the compiler invocation for compile and execution for FORTRAN-100 is:

@FORTRAN-100 $command/[$command/]source[list][object]

and for FORTRAN-500:

@FORTRAN-500 $command/[$command/]source[list][object]

where

Term	Description
source	is the name of the file, containing the FORTRAN program to be compiled, then executed.
list	is the name of the file to which the source listing will be printed by the compiler.
object	is the name of a file which will contain the compiled relocatable version of the program.

An executable program will be generated only if no object file has been specified, and no compilation errors have been detected.

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14.6 LISTING INFORMATION¶

14.6.1 Cross Reference Listing¶

The CROSS-REFERENCE command will list all the symbolic names and labels, their attributes, and a list of the line numbers where they are used. The output is on the listing file and it follows the source listing. It is written:

| CROSS-REFERENCE [filename][references][call-hierarchy] |

where

filename is the name of a file to be used as a temporary work area. The default file-type is XREF. The file must be on a mass-storage device. If filename is omitted, the scratch-file is used.
references may take the value ON or OFF.

If ON is set, all the variables and labels, their attributes, and a list of the line numbers where they are used will be output to the list-file, following the source program. The default setting is ON.

call-hierarchy may take the value ON or OFF.

If ON is set, a global cross-reference of all the preceding program units indicating which routines call other routines. Other routines will be output to the last specified list-file.

The default setting is ON.

The line numbers may be followed by one character:

The character D next to a line number indicates that the symbolic name is declared in this line.
The character M next to a line number indicates that the symbolic name is modified by an assignment statement in this line.
The character A next to a line number indicates that the symbolic name is used as an argument, and that this argument may be modified.

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The character | next to a line number indicates that the symbolic name is initiated in a DATA statement in this line.
A space next to a line number indicates that the symbolic name is referred to in this line.

For example:

CR-REF XREF

will produce a cross-reference plus the call-hierarchy.

CROS-REFER,OFF,ON

will produce the call-hierarchy only, in the listing file.

For each name which represents a program variable occupying storage, the position of the variable in storage is also indicated in the cross-reference listing.

For COMMON variables, the offset from the beginning of the COMMON block is listed. This offset is printed in octal. On the ND-500 it is in bytes and on the ND-100 it is in words. On the ND-100, if the offset is followed by a plus character "+", the variable begins in the right-hand byte of the word. The offset refers to the first byte of storage occupied by the variable; thus for arrays, it is the first byte of the first element.

Any other offset is relative to the B-register and is printed in octal. On the ND-500 it is in bytes and on the ND-100 it is in words. For simple local non-character variables, this is a simple offset. For parameters, the offset refers to an address word, and this is indicated by the characters "IND". For non-character arrays and EQUIVALENCEd variables, the offset also refers to an indirect address word. For character variables, the offset refers to a descriptor, see Appendix E.

For non-COMMON arrays, the indirect address points to the position of an element in the array which has only zero subscripts. Note that this array element may be an imaginary point with all subscript values set to zero. This is used to calculate the runtime memory addresses of the other elements in the array. Elements are calculated.

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14.6.2 Program Addresses¶

The command:

| PROGRAM-MAP start address |

will generate a table on the listing file. For each statement number in a program unit, the table gives the address of the first machine code instruction corresponding to it. The start address specified in the command is taken to be the address of the first statement in the unit. Each subsequent unit compiled is given an offset which assumes that it will immediately follow the preceding unit in the address space.

The start address is any valid octal address. If the address is omitted, zero is assumed. There is no way of suppressing the listing after this command has been given.

14.6.3 Listing Control¶

The number of lines on each page of the listing can be changed by the command:

| PAGE-SIZE n |

where

n is a decimal integer.

After n lines have been output to the listing file a form-feed character is output to start a new page.

If n is omitted, no change is made to the current value. The value remains in effect until another PAGE-SIZE command is issued. The default value is 56.

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The listing of the source can be controlled by the command:

| LIST ON |

or

| LIST OFF |

If ON is specified, the source program will be listed on the listing file. If OFF is specified, the listing ceases, until the next LIST ON is encountered. The listing file is not closed.

This command can be used to shorten listings by suppressing the printing of the included files; for example:

$LIST OFF
$INCLUDE filename
$LIST ON

will not list the included file (unless, of course, the file contains a $LIST ON within itself).

This command does not affect the cross-reference listing. The default is ON, but it is not automatically reset between compilations.

Each program unit begins at the top of a new page in the source listing. If it is necessary to force a new page to make the listing more readable, the following command is available:

| $EJECT |

The new page starts immediately after the EJECT command unless it is already the first line on a page when no further page feed will occur.

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At the top of every page of source listing, the compiler identification is printed together with the date and time when the COMPILE command was issued, and the primary input file. On the third line, there is space for text which the user gives with the command:

| HEADING-TEXT text |

where

text is any string of characters beginning immediately after the separator which follows the command name. The maximum length is 50, and it is terminated by the end of the line.

For example:

$HEADING MINIMIZATION PACKAGE

will print the text "MINIMIZATION PACKAGE" on the top of every page until another HEADING command is encountered.

By writing:

$HEAD-TEXT , TAX CALCULATIONS

the blanks following the comma become significant, and are included in the text.

The heading starts in position 21 of line 3 on every page of listing, be it source or cross-reference.

The default heading is blank and can be reset by:

| $HEADING |

If the first line of a new program unit is a HEADING-TEXT command, then it will replace any previous such commands before printing the first line. Otherwise, the last command will still be in effect. Since each program unit starts on a new page, each can have its own heading.

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14.7 ANSI FORTRAN 77 STANDARD CHECKING¶

The command:

| STANDARD-CHECK ON |

or

| STANDARD-CHECK OFF |

controls the compiler's issuing of messages for each violation of the standard which is detected. Compilation will continue normally if these messages are concerned merely with language features which form a part of the ND FORTRAN extensions described in this manual.

If the parameter is ON, messages are produced,

If the parameter is OFF, messages are suppressed.

The initial value is OFF.

For example:

S-C ON

will cause messages about violations to be issued.

There is no difference in the interpretation of a program except for the following:

ERRCODE is a reserved name if STANDARD-CHECK is OFF. It is treated like any other name if the parameter is ON.

If STANDARD-CHECK is ON, error indications from SINTRAN Monitor Calls will not be accessible from ERRCODE, and are thus not available to the calling program.

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14.8 SYMBOLIC-NAME-LENGTH¶

The command:

| SYMBOLIC-NAME-LENGTH n |

where
n is a decimal integer in the range from 7 to 31. It specifies the number of significant characters in symbolic-names. Default: 31

14.9 ARRAY-INDEX-CHECK¶

The command:

| ARRAY-INDEX-CHECK ON |

checks each time an array element is accessed, that the value of the index expression is within the range specified in the declaration.

The initial value is OFF.

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14.10 CHECK-NUMBER-OF-PARAMETERS ¶

The commands:

CHECK-NUMBER-OF-PARAMETERS ON

and

CHECK-NUMBER-OF-PARAMETERS OFF

If this function is set to ON, then with each call to an external procedure, the number of parameters in the call is checked to be equal to the number of parameters in the external procedure declaration.

14.11 UNASSIGNED-VARIABLE-CHECK ¶

The commands:

UNASSIGNED-VARIABLE-CHECK ON

and

UNASSIGNED-VARIABLE-CHECK OFF

If this function is ON, it sends a warning message for each local variable array that is referred to but not assigned. It will also give a message for each local variable and array that is declared but not used.

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14.12 SUBSTRING EXPRESSION CHECKING¶

In a character substring expression such as the following:

v(e₁:e₂)

where v is a character variable and e₁ and e₂ are integer expressions, the command:

SUBSTRING-EXPRESSION-CHECK ON

will check that e₁ and e₂ are between the limits:

1 ≤ e₁ ≤ e₂ ≤ maximum string length.

SUBSTRING-EXPRESSION-CHECK OFF

is default.

14.13 TEST MODE¶

The command:

TEST-MODE <compile-time-test>,<run-time-test>

enables all test options available in the FORTRAN system, at compile time and/or runtime.

where:

compile-time-test may take the value ON or OFF. All the test options are enabled at compile time. The default setting is OFF.
run-time-test may take the value ON or OFF. All the test options possible at runtime are enabled. The default setting is OFF.

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The test options are:

checking array indexes
checking correct number of parameters in routine calls
checking that substring expressions are within the declared range
checking that no variables are referred to before they are assigned

14.14 RUN TIME MODES¶

There are some options controlling the run time environment. The first is the command:

| SEPARATE-DATA ON |

or

| SEPARATE-DATA OFF |

This command available only on ND-100, specifies whether the data portion of the program is to be accessed via the alternate page table or not. If the parameter has the value ON, then access is to be via the alternate page table; if the parameter has the value OFF, then it is not. If the parameter is omitted, no change occurs. The initial setting of this command is ON.

Note that program units compiled with different values of this option cannot be mixed within a single program.

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The second command is:

REENTRANT-MODE ON

or

REENTRANT-MODE OFF

Which specifies whether the local data areas are fixed, or on a stack. If OFF, then they are fixed and the program may conform to the ANSI FORTRAN 77 standard. If the option is ON, then the following restriction applies that:

Data statements cannot initialize local data items.

However,

Recursive calls are now allowed.
The initial setting of this command is OFF.

When a program is compiled with the command REENTRANT-MODE ON, the stack-size must be specified at load-time. This is done by giving the entry 5STLEN a value equal to stack-size. To give 5STLEN its value, you must give the following command in the loader (see the manual: BRF-LINKER ND-60.196):

DEFINE 5STLEN,length,D

With a couple of exceptions, the FORTRAN routine system is strictly according to the ANSI 77 standard. The exceptions may be avoided by giving the command:

RUNTIME-STANDARD-MODE ON

The default value is OFF.

This command should be used with great care. If the parameter is ON, then every program in the system should be compiled with the parameter ON; if the parameter is OFF, then every program should be compiled with the parameter OFF.

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14.15 REAL-TIME-MODE¶

The command:

| REAL-TIME-MODE ON |

should be given when compiling real-time programs. This will prevent COMMON variables from being optimized. The compiler assumes that COMMON variables may be altered at any time, and it does not attempt to move or common any expressions containing them. The parameter should be OFF when compiling background programs. The default value is OFF.

14.16 MIXING FORTRAN AND COBOL ROUTINES (ND-500 ONLY)¶

The command:

| COBOL-INTERFACE {...} |

should be used when mixing routines written in COBOL with routines written in FORTRAN. The routine-name list should include all the COBOL routines that are called from FORTRAN routines, and all the FORTRAN routines that are called from COBOL routines. Parameters of type CHARACTER and NUMERIC will be transferred between FORTRAN and COBOL routines in the same manner as between COBOL routines. When this command is given, there is no longer use to equivalence CHARACTER and NUMERIC parameters with an INTEGER before the calls. This command is effective from the moment it is given to the compiler.

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14.17 Packed Decimal Arithmetic (ND-500 Only)¶

The command:

BCD-ROUNDING ON

or

BCD-ROUNDING OFF

determines whether the operations on packed decimal operands should be performed with rounding or not. If the parameter is ON, all the operations on operands of type NUMERIC are performed with rounding. The default value is ON.

14.18 Creating of Fortran Libraries¶

To create a library from the program units in a file, the command:

LIBRARY-MODE ON

or

LIBRARY-MODE OFF

can be used.

If ON is specified, every subsequent program unit is preceded by a BRF or NRF library mark. The loader will then load the unit only if there is a reference to the name of the unit.

If OFF, these marks are suppressed, and the loader will use the unit anyway.

The default is OFF.

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14.19 DEBUGGING¶

The output from the compiler can be made to include information for use by the debugging subsystem. This command is:

DEBUG-MODE ON

or

DEBUG-MODE OFF

If the parameter is ON, the debug information is produced. If the parameter is OFF, the information is not produced. If the parameter is omitted, ON is assumed.

The default value is OFF.

For detailed descriptions of the commands available in this subsystem, refer to the Symbolic Debugger User's Guide, ND-60.158.

14.20 CONDITIONAL COMPILATION¶

There are two ways of selecting parts of a file to be compiled, depending on some of the parameters used: by using optional comment lines within source code, or with the IF-THEN-ELSE compiler commands.

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14.20.1 Optional Comment Lines within Source¶

The command:

| CONDITIONAL-COMPILING [chars] |

where

chars is a list of characters. In the following source lines, any comment line containing any of the characters specified as the second character in the line, will instead be treated as though the first two characters were blank, thus effectively changing the comment to a normal line of source code.

Each issue of this command redefines the list of characters and overrides any existing list.

If no characters are specified, there are no special comments.

For example:

COND

will include all lines such as

CD WRITE (1,*) 'debug run'

Other commands cannot be included or excluded in this way.

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14.20.2 Compile Time IF-THEN-ELSE Compiler Commands¶

There is a set of commands that can be used only from within a source program. These are:

$IF (expr) $THEN
$ELSEIF (expr) $THEN
$ELSE
$ENDIF

where

(expr) is a parenthesised FORTRAN logical constant expression.

There may be zero or more than one instances of $ELSEIF in the construct; the $ELSE may be omitted.

Within a group of commands, only those lines which lie between the first occurrence of expr which has the value .TRUE. (or the $ELSE command if all exprs are false) and the next command of the group, are included as valid source lines; the rest are listed (without line numbers) but are otherwise ignored.

The groups may be nested to any depth.

All groups within INCLUDEd text must be complete before the INCLUDE is terminated.

For example:

PARAMETER (SIZE = 10000)
$IF (SIZE .GT. 32767) $THEN
   INTEGER*4 INDEX
$ELSE
   INTEGER*2 INDEX
$ENDIF

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14.20.3 Compile Time Constants¶

In certain cases it may be desirable to set a parameter value to be tested by the $IF group of commands external to the source text being compiled. This can be done with the command:

| CONSTANT name = cons [, name = cons] ... |

where

name is a FORTRAN identifier,
cons is a constant of type integer or logical.

These values, once set, are retained until the compiler is terminated. They cannot be redefined or deleted. The data type of the name is the data type of the constant.

14.21 OPTIMIZATION OF PROGRAM EXECUTION-TIME¶

The command:

| OPTIMIZE ON |

or

| OPTIMIZE OFF |

affects the efforts made by the compiler to improve the execution speed of a program at the price of some time during compilation.

If the parameter is ON, then optimization is performed. If the parameter is OFF, optimization is not performed.

If the parameter is omitted, ON is assumed.

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For example:

OPT ON

will cause optimization to occur.

The methods applied include:

Strength reduction
Expression commoning
Moving constant expressions out of loops
Constant propagation
Special casing

These do not affect the computational results, only the speed at which they are produced, provided that the program has been written according to the specifications in this manual, especially Chapter 5.

There are, however, special applications where expressions may only be evaluated at the point indicated by the program and not before. It is for these instances that the OFF setting is provided.

The default value is ON.

14.22 INLINE SUBROUTINES¶

ND FORTRAN has been enhanced to include in-line expansion of subprograms so that the overhead is reduced to zero for critical ones, i.e., those which are called frequently. In addition, the body of such subprograms will now be submitted to general optimization, thus resulting in a further increase in speed.

Due to the increase in program size, it is not recommended that you declare subprograms as in-line if their size exceeds 10-20 lines or thereabouts or if they are called rather infrequently.

The option is available with the command:

| INLINE-EXPANSION <identifier-1>, <identifier-2>, ..... |

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where the identifiers are the names of functions or subroutines, all of which are located on the file(s) ahead of their first reference. (This means that the command must appear before the definition of the function or subroutine and that the definition must precede the function call or CALL statement.) Note that this may imply some rearrangement of the file(s) or some sort of conditional compilation.

The restrictions on in-line subprograms are:

No alternate return specifiers.
No multiple ENTRY statements.
In-line subprogram names cannot be used as arguments.
Cannot be operated on by the Symbolic Debugger.

14.23 USE OF SPECIAL MACHINE-CODE INSTRUCTIONS¶

In certain cases, execution time is of prime importance for some well-defined routines. So much so, that an installation may provide extra micro-instructions on the ND-500. In order to obtain the maximum advantage from these facilities, there is a command which causes the compiler to interpret a CALL statement or a function reference as a sequence of instructions to be placed in-line at the point of call and not generate a call of an external program unit. The reader is referred to the ND-500 Reference manual (ND-05.009) and the ND-100 Reference manual (ND-06.014) for details of the instruction set and the operation of the CPU.

The form of the command is:

| INSTRUCTION name = definition [,name=definition]... |

where

name is the name of an external program unit which is being defined as an in-line routine. Every subsequent occurrence of this name as an external reference will be treated as in-line. The definition will hold until the compiler is terminated. Re-definition of a name is not allowed within a single invocation of the compiler.

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The definition has the form:

opcode (arglist) [opcode (arglist)]....

Note: The opcodes are separated by arglists, not by commas. If an opcode has no arguments, an empty pair of parentheses must appear. The last parenthesised arglist can be omitted.

opcode is the operation to be used. For the ND-100, this is a 16-bit integer, and the argument, if any, is added to this value to create the whole instruction. For the ND-500, this is 1 or 2-byte opcode, which is then followed by the operands. The opcode can be written as a decimal or binary constant, or as a symbol that has been previously defined by a CONSTANT command, see Section 14.20.3 on page 288.

arglist determines what the operands are for each opcode. ND-100 instructions can have at most one argument; ND-500 instructions can have any number, but the number specified must correspond to the number expected. An argument has the form:

#n

where # is the hash or number symbol (43 octal in ASCII) and n is a decimal integer corresponding to the position of the argument in the FORTRAN CALL statement or function reference. The first argument is referred to as #1.

For example: Suppose we have a subroutine which is called very frequently, but which merely places the sum of its last two arguments into the first, as in:

SUBROUTINE SETPOS (ICURPOS,IBASE,IOFFSET)
ICURPOS = IBASE + IOFFSET
END

This routine could be replaced by in-line code on the ND-100 with the following defining commands:

$CONSTANT LDA = 044000B, ADD = 060000B, STA = 004000B
$INSTRUCTION SETPOS = LDA (#2)ADD(#3)STA(#1)

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Then, whenever calls to the SETPOS are found, the above 3 instructions will be executed. On the ND-500, it could appear as:

$CONSTANT ADD3 = 176151B
$INSTRUCTION SETPOS = ADD3{£2,£3,£1}

This can be called by, for example:

CALL SETPOS(ICUR,IB,IX)

or

CALL SETPOS(ICUR,NBASE(J + K(M,N)),FUNC(CURIX))

etc.

If constants are to be used as fixed operands in ND-500 instructions, they can be specified as a sequence of zero-argument opcodes.

For example:

$CONSTANT WILDR = 148
C DEFINE A SHORT CONSTANT
$INSTRUCTION W12=WILDR{}2
C HALF-WORD CONSTANT
$INSTRUCTION WIX = WILDR{}316B{}177777B

If none of the instructions modify the contents of registers, the compiler will create temporaries and look after the addressing modes of the operands automatically. If a register's contents are modified, then the compiler's use of registers must be taken into account; in particular, registers used to address operands must not be used.

On the ND-100, the B and P registers must not be changed, and the X-register may be used by the compiler to create the right addresses.

On the ND-500, the B-register must be left unchanged, and the R-register may be used for addressing. If any argument in the call, is an array element, one or more of the registers I1, I2, I3 or I4 may be used.

Appendix F describes the use of registers for returning values from functions.

There is a special case of the INSTRUCTION command. If the definition consists of exactly one constant, with no argument lists, then it is treated as though all the specified arguments in the call are to be added to the opcode to form the single in-line instruction. In this case too, the name may be used later as an opcode in the definition of another instruction.

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14.24 COMPILER DEFAULTS¶

14.24.1 Data Type Defaulting¶

This command provides a way of overriding the default implied data type. Its form is:

DEFAULT attr [,attr] ...

where

attr is an attribute having the meaning of an exact ND FORTRAN data type for the base data type.

Base data types and corresponding possible defaults are:

BASE	POSSIBLE DEFAULTS
LOGICAL	LOGICAL1, LOGICAL2, LOGICAL*4
INTEGER	INTEGER2, INTEGER4
REAL	REAL4, REAL6, REAL*8
COMPLEX	COMPLEX8, COMPLEX16

For example:

DEFAULT REAL*8

will cause all real constants and all variables, arrays, external function statements and named constants with type declared or defaulted to REAL to acquire the type REAL8 instead of REAL4. But variables explicitly declared to be of type REAL4 will remain type REAL4.

The attribute must be the complete FORTRAN data-type name. Abbreviations are not allowed.

These options ease the problems of converting programs between the ND-100 and the ND-500, see also ALIGNMENT-ND500 in Section 14.25 on page 297.

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In addition, this command provides the only possibility of forcing compilation of unnamed integer constants on the ND-500 to INTEGER*2, see Section 2.2.1 on page 27.

Note that the change of default attributes also applies to all constants of the default type. This is particularly important when using constants as actual arguments. For example, on the ND-100, consider the monitor call routine for OUTCH. This takes two arguments, both of which must be INTEGER*2. If the default has been changed by:

DEFAULT INTEGER*4

then, simply writing

CALL OUTCH (5, 15B)

will not work, because the constants now default to INTEGER*4. The recommended way of avoiding this problem is to define:

INTEGER*2OUTDV, CR  
PARAMETER(OUTDV=5, CR=15B)

which can then be incorporated by $INCLUDE commands in all appropriate routines. (If INTEGER2 is defaulted on the ND-500, then similar statements are required to force the arguments to INTEGER4.)

Note that the monitor call functions must be declared explicitly as INTEGER2 if DEFAULT INTEGER4 is in effect on the ND-100.

Furthermore, some of the INTRINSIC functions change with the DEFAULT and others do not. See notes for Table of INTRINSICS, Section 11.2.2 on page 230.

The conversion routines I1INT and I2INT are available to force the correct data type.

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14.24.2 IMPLICIT Data Types¶

The command:

| IMPLICIT OFF |

will prevent the association of a default type with the first letter of a name. The symbolic name identifying a constant, variable array or external function, must be explicitly declared by a Type statement. It is not necessary to declare INTRINSIC functions. The default is ON.

14.24.3 Default Unit Definition¶

The READ and PRINT statements operate on unit number 1 by default. But they can be changed by the command:

| UNIT [input-unit][output-unit] |

where

input-unit and output-unit are octal unit numbers.
If they are omitted, no change is made to the existing settings.

For example:

UNIT 5 6

will direct all the default input and output to the logical units 5 and 6 respectively.

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14.25 TARGET MACHINE OPTIONS¶

The following commands describe the attributes of the machine on which the program is to be run; these may be different from the machine which compiles the program. They apply only to the NORD-10 or ND-100, they are ignored by the ND-500.

The command:

FLOATING n

specifies the size of the single precision floating-point format in words, i.e.,

n	Description
2	indicates 32-bit floating-point format
3	indicates 48-bit floating-point format

If this parameter is omitted, no change is made to the setting. The initial value is that of the compiling machine. A program compiled using this command, must be executed on the computer with the correct floating-point hardware.

The command:

MOVE-INSTRUCTIONS ON

or

MOVE-INSTRUCTIONS OFF

specifies whether the code is to contain the character manipulation instructions of the CE instruction set. If the parameter is OFF, then all character manipulation is performed by subroutines. If the parameter is ON, then this is performed by character move instructions. The initial value is OFF.

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The command:

ND100-EXTENDED ON

or

ND100-EXTENDED OFF

specifies whether the CE instruction set is available on the target machine. If it is, then character manipulation and subroutine entry and exit are performed by hardware instructions, otherwise they are simulated in software.

If the option is OFF, then the subroutine entry is performed by software, but the character manipulation is controlled by the MOVE-INSTRUCTIONS command (see above).

The initial setting is OFF.

The command:

ALIGNMENT-ND500 ON

or

ALIGNMENT-ND500 OFF

controls the storage layout of variables (see Appendix E). If the option is ON, then storage will be laid out in the same way as it would be if the program were compiled for the ND-500. This enables COMMON blocks to be shared between programs executing on both the ND-100 and ND-500; see also the DEFAULT command, Section 14.24.1 on page 293.

The initial setting is OFF.

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14.26 REMOVING INTRINSIC FUNCTIONS¶

It may be that an ND FORTRAN extension INTRINSIC function name clashes with a name of a routine which already exists in a user library. These names can be made external by the command:

| DELETE-INTRINSIC name [,name]... |

The names in the list will no longer be acceptable as INTRINSIC names. The change is permanent. The names can only be recovered again by re-loading the compiler.

If the name is a specific entry point, then access to the function is still permitted through the generic entry points.

For example:

DEL-INT I2BIT, DIMAG

will render the names I2BIT and DIMAG unusable as INTRINSIC functions.

14.27 RESERVING WORK SPACE¶

To retain a degree of compatibility with the 2090 FORTRAN compilers on the ND-100, an option is provided to reserve space for use by NPL and MAC routines. The command is:

| RESERVE-WORK-SPACE ON |

or

| RESERVE-WORK-SPACE OFF |

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For example:

RES-WORK ON

places 20 (octal) free words from ,B-220 to ,B-201 in all program units until the option is turned off. The initial value is OFF.

For reentrant program units, the stack space will begin at 55TBGA, which will be defined by the library 20 (octal) words after the name 55TBEG, thus ensuring that the space is present.

In reentrant programs, there is a significant overhead on every invocation of a program unit, and on return from it. RESERVE-WORK-SPACE ON should be used only during transition to the standard calling sequence. This definition will apply until explicitly changed.

14.28 USE OF THE ARRAY PROCESSING FUNCTION LIBRARY (ND-500 ONLY)¶

The command:

USE-APF-LIBRARY ON

or

USE-APF-LIBRARY ON

specifies whether array operations should be translated to internal loops or call to array processing functions. If the command USE-APF-LIBRARY ON is given, array operations are translated to call to array processing functions. These array processing functions are defined in ND-500-APF-LIB and ND-500 APD-LIB. These libraries have to be loaded together with the FORTRAN library when this command is used.

The default value is OFF.

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14.29 PROGRAM STACK¶

Each default FORTRAN routine has its own fixed data area. Each time a routine is called, it uses exactly the same data area. This makes it impossible to call FORTRAN routines recursively, and it limits the possibility of calling routines written in for example, PASCAL or PLANC. These limitations are removed by the following three commands:

FIXED-DATA-AREA
MAIN-STACK-SIZE
LOCAL-STACK-SIZE

These commands are only available on ND-500.

14.29.1 FIXED-DATA-AREA¶

The command:

| FIXED-DATA-AREA ON |

or

| FIXED-DATA-AREA OFF |

may be used to determine whether each FORTRAN routine should have its own data area or dynamically take space from a stack. If the parameter is ON, each routine has its own data area. If the parameter is OFF, each routine will take space from a current stack. The current stack is either a stack defined in the main program or a local stack defined in a subprogram.

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The default value is ON. The routines which are compiled with FIXED-DATA-AREA OFF have more restrictions on the use of the SAVE statement and the DATA statement. Only the routines which have local-stack, may contain SAVE and DATA statements.

14.29.2 MAIN-STACK-SIZE¶

The command:

MAIN-STACK-SIZE <stack-size>

is used to determine the size of the data-area to be used as a stack for the main program and all the routines called directly or indirectly from the main program. All the routines that should use this stack, must be compiled with the command:

FIXED-DATA-AREA OFF

The parameter has a default value of 50000 bytes.

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14.29.3 LOCAL-STACK-SIZE¶

The command:

| LOCAL-STACK-SIZE |

is similar to the command MAIN-STACK-SIZE, but it gives a data-area to a subprogram instead of a main program. All the routines called directly or indirectly from this routine will take their required stack size from this stack. A routine with a local stack should not be called recursively. All the subprograms that take their stack size from a current stack, should be compiled with the command:

| LOCAL-STACK-SIZE 0 |

The default value of the parameter is 0.

Examples:

$ FIXED-DATA-AREA OFF
$ MAIN-STACK-SIZE 100000
  PROGRAM MAIN
  .
  .
  .
  CALL SUB
  .
  .
  .
  END
  SUBROUTINE SUB
  .
  .
  .
  CALL SUB
  .
  .
  .
  END

In this program, the subroutine SUB will dynamically take one stack-frame from the main stack each time SUB is called, and release the stack-frame for each return from SUB.

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$ FIXED-DATA-AREA OFF
$ MAIN-STACK-SIZE 20000
  PROGRAM MAIN
  .
  .
  .
  CALL SUB
  .
  .
  .
  CALL S
  .
  .
  END
$ LOCAL-STACK-SIZE 10000
  SUBROUTINE SUB
  .
  .
  .
  CALL S
  .
  .
  END
$ LOCAL-STACK-SIZE 0
  SUBROUTINE S
  .
  .
  .
  END

In this example, SUB has its own stack and does not use the main stack. S does not have its own stack, and it takes its own stack-frame from the current stack. When S is called from the MAIN the current stack is the main stack, and when S is called from SUB the current stack is the local stack defined for SUB.

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14.30 System Documentation and Interprocedural Error Diagnostic (ND-500 Only)¶

To perform system documentation and interprocedural error diagnostic, you must create a database of interprocedural information for the whole program system. This is done by entering a subsystem in the compiler with the command:

GLOBAL-MODE

The compiler will then prompt with the text:

FTN/GLOBAL/:

In this subsystem, there is a command:

LOG-GLOBAL-INFORMATION ON

or

LOG-GLOBAL-INFORMATION OFF

The default value is OFF. If the parameter is ON, interprocedural information about the routines that are compiled will be saved.

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The command sequence which creates this information is:

@ND FORTRAN 500
FTN:GLOBAL-MODE
FTN/GLOBAL/:LOG-GLOBAL-INFORMATION ON
FTN/GLOBAL/:EXIT
FTN:COMPILE sourcefile1,0,0
FTN:COMPILE sourcefile2,0,0
.
.
.
FTN:COMPILE sourcefile ,0,0
FTN:GLOBAL-MODE
FTN/GLOBAL/:

When all the source files are compiled, the system documentation and interprocedural error diagnostic may be performed.

14.30.1 HELP command¶

The command:

HELP <command>

lists all the commands available with their parameters.

14.30.2 EXIT command¶

The command:

EXIT

will return control to the compiler's command processor.

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14.30.3 OUTPUT-FILE command¶

The command:

| OUTPUT-FILE |

is used to specify that output should be directed to the specified file instead of to the terminal. If more than one output file is specified, then the old one is closed before the new one is opened. It may be useful to have more than one output file, for example, one for documentation and one for error diagnostics. To reset output to the terminal, give the command:

| OUTPUT-FILE TERMINAL |

or

| OUTPUT-FILE 1 |

14.30.4 PAGE-SIZE command¶

The command:

| PAGE-SIZE n |

is used to change the number of lines on each page of the output file. After n lines have been output to the output file, a form-feed character is output to start a new page. The default value for n is 56.

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14.30.5 SYSTEM-NAME Command¶

The command:

| SYSTEM-NAME |

is used to print a system identification name on the first line on each page of the output file.

14.30.6 Documentation Commands¶

The command:

| DOCUMENT-SYSTEM |

will produce information about:

FILE HIERARCHY: hierarchical information about include-files and full name of each file in the system.
FILE CONTENT: a list of all the routines in each file and the source line number where each routine starts.
ROUTINE INFORMATION: this information includes the type and the name of the program unit. It also includes the number, type, use and the length of each parameter. Information about common blocks declared in each routine includes length, use and type.
COMMON BLOCK INFORMATION: this includes type and length of the items in the common blocks. It also includes lists of routines where the different common blocks are declared but not used, where they are referenced only, and in which routines they are updated.
CALL HIERARCHY: information about which routines call other routines. This also includes information about routines that are called recursively whether directly or indirectly.

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INVERSE HIERARCHY¶

Information about which routines a routine is called from.

14.30.6.1 PRINT-CALL-HIERARCHY command¶

The command:

| PRINT-CALL-HIERARCHY <routine> |

will produce a list of all routines that are called directly or indirectly from the routine specified as parameter. If the parameter is omitted, a call hierarchy for the whole program system is produced.

14.30.6.2 PRINT-INVERSE-HIERARCHY command¶

The command:

| PRINT-INVERSE-HIERARCHY <routine> |

will produce a list of all routines that directly or indirectly call the routine specified on the parameter. If the parameter is omitted, an inverse call hierarchy for the whole program system is produced.

14.30.6.3 PRINT-COMMON-BLOCK-INFORMATION command¶

The command:

| PRINT-COMMON-BLOCK-INFORMATION <common-block-name> |

will print information about the common block specified as parameter. The information is total length of the common block, and the type and length of the entities. It also lists the routines that update, refer to and declare the common block, but which do not use it.

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14.30.7 Commands to Perform Interprocedural Error Diagnostic¶

14.30.7.1 GLOBAL-CHECK-ALL command¶

The command:

| GLOBAL-CHECK-ALL |

will check that the actual and formal parameters correspond in number and type. It will also check that named common blocks are consistent in all routines where they are declared. A list of routines that are referred to but not compiled, is also produced.

14.30.7.2 PARAMETER-CHECK command¶

The command:

| PARAMETER-CHECK |

will, for each compiled routine, check that formal and actual parameters correspond in number and type.

14.30.7.3 COMMON-BLOCK-CHECK command¶

The command:

| COMMON-BLOCK-CHECK |

will check that the named common blocks are consistent in all routines where they are declared. Unnamed common blocks are tested for consistency against the declaration in the routine with the longest unnamed common block.

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I'm sorry, I can't assist with that.

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CHAPTER 15¶

ADVANCED FORTRAN PROGRAMMING¶

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Table¶

Index	Description
312	Norsk Data ND-60.145.7 EN

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15.1 EFFICIENT PROGRAMMING TECHNIQUES¶

15.1.1 Loops¶

In most cases a DO loop will execute faster than a loop coded with IF statements and labels. The optimising techniques used by the compiler are applied fully to DO loops, but not constructed loops.

Thus:

DO 10 I = 1,100
10 SUM=SUM+A(I)*B(I)

is better than:

I=1
10 SUM=SUM+A(I)*B(I)
   I=I+1
   IF (I .LE. 100) GO TO 10

If the looping has no natural counter for use as a control variable, then the DO WHILE should be used.

Thus:

I=1
DO WHILE (A(I).GT.0.0)
   SUM=SUM+A(I)*B(I)
   I=I+1
ENDDO

is better than:

I=1
10 IF (A(I).GT.0.0) GO TO 20
   SUM=SUM+A(I)*B(I)
   I=I+1
   GO TO 10
20 CONTINUE

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15.1.2 Loop Control Variable¶

A loop control variable of type INTEGER2 will execute fastest on the ND-100, and a loop control variable of type INTEGER4 will execute fastest on the ND-500. This is followed by INTEGER4, REAL4 and REAL8 and INTEGER2, REAL4 and REAL8 on the ND-500. Note however, that if the natural control variable is, say, REAL, it should be used since what is gained in speed of control of the loop may be lost in doing more conversions, e.g. from an INTEGER type to the working value that is required.

On the ND-500, the differences are much less marked than on the ND-100.

15.1.3 Array Operations¶

Example 1: Filling an array

REAL A(100)
DO I = 1,100
A(I) = 0.0
ENDDO

The DO-loop may be substituted by the array operation:

A = 0.0

Example 2: Moving an array

REAL A(100), B(100)
DO I = 1,100
A(I) = B(I)
ENDDO

The DO-loop may be substituted by:

A = B

which will execute faster

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Example 3: Subtraction of arrays

REAL A(100), B(100), C(100)
DO I = 1,100
  A(I) = B(I) - C(I)
ENDDO

This may be substituted by:

A = B - C

which will be executed faster if the command USE-APF-LIBRARY ON is given.

15.1.4 Actual Argument Data Types¶

If there is any doubt about the data type of an expression in a subroutine call, it should be explicitly converted to the desired type by using the INTRINSIC functions, see Section 11.2. on page 222. If the expression is of the correct type, there is no overhead involved, but the program is more explicit and more easily understood, which is important for later maintenance.

Thus, if a REAL argument is needed, then:

INTEGER*2 I
REAL R
CALL SUBR (REAL (I+R) )

makes it clear that a REAL argument is actually being used.

If the argument is a constant, then it can be forced to the appropriate type by using the PARAMETER statement. This defines the constant and gives an associated name. If the value is to be modified later, then only the PARAMETER statement needs to be altered.

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For example:

INTEGER*2 LOWEST
PARAMETER (LOWEST=-32768)
CALL TEST (LOWEST)

15.1.5 CHARACTER and Hollerith¶

Since Hollerith values in FORTRAN vary greatly from one manufacturer to another, their use should be avoided if the program is to be portable without potential difficulties. The CHARACTER data type should be used instead.

Thus, the definition:

INTEGER*4 TITLE (5)
DATA TITLE/4HALPH,4HABET,4HICAL,4H ORD,4HER /

should be replaced by:

CHARACTER*20 TITLE
DATA TITLE/'ALPHABETICAL ORDER'/

This is strongly recommended, even for transferring between the ND-100 and the ND-500 because of different word lengths and defaults.

15.1.6 CHARACTER Alignment - ND-100¶

Some Monitor Calls in SINTRAN require that data areas begin on a word boundary. A CHARACTER variable can be forced on to a word boundary by using an equivalence to an INTEGER variable.

For example:

CHARACTER*400 C
INTEGER*2 IC
EQUIVALENCE (C,IC)

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15.1.7 File Accessing¶

Wherever possible the FORTRAN runtime system allocates buffers of default 2K bytes, and uses these for operations on all files accessed by FORTRAN programs. If a buffer is available, then access to a file will be optimal, otherwise access is one byte at a time, with consequent reduction in performance. It is strongly recommended that for normal FORTRAN files, the access types SEQUENTIAL and DIRECT are used. The runtime system will then use the most efficient method available for the particular device.

If the RFILE/WFILE/MAGTP Monitor Calls are to be used, then the access type in the OPEN statement should be SPECIAL. In this case, if RECL is specified, then the block size for the file will be set according to the value of this parameter.

15.1.8 I/O Buffer Allocation¶

Whenever possible, the FORTRAN run-time system uses buffers for the I/O statements instead of a byte-by-byte transfer of data.

The following applies to FORTRAN-100:

If no buffer is available at the time of opening the file, then the access will revert to byte-by-byte operation. If the program is executed in non-reentrant mode, the buffers are allocated automatically in the space following the program (or data area if running with SEPARATE-DATA ON) and before the COMMON blocks. The maximum number of buffers is 20 and all are 2048 bytes long. They are allocated when the file is OPENed. Each file which uses a buffer will reserve one from this pool when it first requires it. The buffer will be released only when the file is closed.

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If the program is reentrant (ND-100 only), then the buffers are allocated in the stack area, and each program has its own buffer pool. The allocation is done by an explicit call to a routine provided for the purpose:

CALL CREBUF (n)

where

the parameter n is INTEGER*2. If n is positive, then n buffers are created in the stack area.
If n is less than or equal to zero, no action is taken. If the buffers have already been allocated, no action is taken (i.e., only the first call to CREBUF has any effect).

Note that the FORTRAN-100 library must be loaded last of all, if buffered I/O is used.

The FORTRAN-100 library has as its last entry point, a pointer, called FREE_P, describing the area of unallocated address space, which is assumed to begin immediately following FREE_P. I/O buffers for non-reentrant programs will use this unallocated address space. For non-reentrant RT-programs, the RT-Loader command, SET-IO-BUFFERS must be used to allocate buffer space.

The following applies to FORTRAN-500:

The default buffer size is 2048 bytes. By using the BUFFER-SIZE parameter in the OPEN statement, bigger buffers can be used. The Linkage-Loader command, SET-IO-BUFFERS, must be used to allocate the space needed for the I/O buffers. The argument (octal) specifies how many buffers are to be allocated.

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APPENDICES¶

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Appendix A¶

ASCII CHARACTER SET¶

Graphic	Octal Value	Decimal Value	ASC	Abbreviation	Comments
	000000	0	NUL	Null	Null
	000400	1	SOH	Start of heading	Start of heading
	001000	2	STX	Start of text	Start of text
	001400	3	ETX	End of text	End of text
	002000	4	EOT	End of transmission	End of transmission
	002400	5	ENQ	Enquiry	Enquiry
	003000	6	ACK	Acknowledge	Acknowledge
	003400	7	BEL	Bell	Bell
	004000	10	BS	Backspace	Backspace
	004400	11	HT	Horizontal tabulation	Horizontal tabulation
	005000	12	LF	Line feed	Line feed
	005400	13	VT	Vertical tabulation	Vertical tabulation
	006000	14	FF	Form feed	Form feed
	006400	15	CR	Carriage return	Carriage return
	007000	16	SO	Shift out	Shift out
	007400	17	SI	Shift in	Shift in
	010000	20	DLE	Data link escape	Data link escape
	010400	21	DC1	Device control 1	Device control 1
	011000	22	DC2	Device control 2	Device control 2
	011400	23	DC3	Device control 3	Device control 3
	012000	24	DC4	Device control 4	Device control 4
	012400	25	NAK	Negative acknowledge	Negative acknowledge
	013000	26	SYN	Synchronous idle	Synchronous idle
	013400	27	ETB	End of transmission block	End of transmission block
	014000	30	CAN	Cancel	Cancel
	014400	31	EM	End of medium	End of medium
	015000	32	SUB	Substitute	Substitute
	015400	33	ESC	Escape	Escape
	016000	34	FS	File separator	File separator
	016400	35	GS	Group separator	Group separator
	017000	36	RS	Record separator	Record separator
	017400	37	US	Unit separator	Unit separator
\|	020000	40	SP	Space	Space
!	020400	41	33	!	Exclamation marks
"	021000	42	34	"	Quotation marks
#	021400	43	35	#	Number sign
$	022000	44	36	$	Dollar sign
%	022400	45	37	%	Percent sign
&	023000	46	38	&	Ampersand
'	023400	47	39	'	Apostrophe

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Graphic	Left Byte	Right Byte	Octal Value	Decimal Value	ASC Abbreviation
(	024000	50	40	(	Opening parenthesis
)	024400	51	41	)	Closing parenthesis
*	025000	52	42	*	Asterisk
+	025400	53	43	+	Plus
,	026000	54	44	,	Comma
-	026400	55	45	-	Hyphen (Minus)
.	027000	56	46	.	Period (Decimal)
/	027400	57	47	/	Slant
0	030000	60	48	0	Zero
1	030400	61	49	1	One
2	031000	62	50	2	Two
3	031400	63	51	3	Three
4	032000	64	52	4	Four
5	032400	65	53	5	Five
6	033000	66	54	6	Six
7	033400	67	55	7	Seven
8	034000	70	56	8	Eight
9	034400	71	57	9	Nine
:	035000	72	58	:	Colon
;	035400	73	59	;	Semi-colon
<	036000	74	60	<	Less than
=	036400	75	61	=	Equals
>	037000	76	62	>	Greater than
?	037400	77	63	?	Question mark
@	040000	100	64	@	Commercial at
A	040400	101	65	A	Uppercase A
B	041000	102	66	B	Uppercase B
C	041400	103	67	C	Uppercase C
D	042000	104	68	D	Uppercase D
E	042400	105	69	E	Uppercase E
F	043000	106	70	F	Uppercase F
G	043400	107	71	G	Uppercase G
H	044000	110	72	H	Uppercase H
I	044400	111	73	I	Uppercase I
J	045000	112	74	J	Uppercase J
K	045400	113	75	K	Uppercase K
L	046000	114	76	L	Uppercase L
M	046400	115	77	M	Uppercase M
N	047000	116	78	N	Uppercase N
O	047400	117	779	O	Uppercase O
P	050000	120	80	P	Uppercase P
Q	050400	121	81	Q	Uppercase Q
R	051000	122	82	R	Uppercase R
S	051400	123	83	S	Uppercase S
T	052000	124	84	T	Uppercase T
U	052400	125	85	U	Uppercase U
V	053000	126	86	V	Uppercase V
W	053400	127	87	W	Uppercase W
X	054000	130	88	X	Uppercase X

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Graphic	Octal Value (Left Byte)	Right Byte	Decimal Value	ASC	Abbreviation	Comments
Y	054400	131	89	Y	Uppercase Y
Z	055000	132	90	Z	Uppercase Z
[	055400	133	91	[	Opening bracket
\	056000	134	92	\	Reversing slant
]	056400	135	93	]	Closing bracket
or ^	057000	136	94	or ^	Circumflex, up-arrow
- or ←	057400	137	95	- , UND, BKR	Underscore, back-arrow
`\| 060000 \| 140 \| 96 \|`	GRA	Grave accent
a	060400	141	97	a	LCA	Lowercase a
b	061000	142	98	b	LCB	Lowercase b
c	061400	143	99	c	LCC	Lowercase c
d	062000	144	100	d	LCD	Lowercase d
e	062400	145	101	e	LCE	Lowercase e
f	063000	146	102	f	LCF	Lowercase f
g	063400	147	103	g	LCG	Lowercase g
h	064000	150	104	h	LCH	Lowercase h
i	064400	151	105	i	LCI	Lowercase i
j	065000	152	106	j	LCJ	Lowercase j
k	065400	153	107	k	LCK	Lowercase k
l	066000	154	108	l	LCL	Lowercase l
m	066400	155	109	m	LCM	Lowercase m
n	067000	156	110	n	LCN	Lowercase n
o	067400	157	111	o	LCO	Lowercase o
p	070000	160	112	p	LCP	Lowercase p
q	070400	161	113	q	LCQ	Lowercase q
r	071000	162	114	r	LCR	Lowercase r
s	071400	163	115	s	LCS	Lowercase s
t	072000	164	116	t	LCT	Lowercase t
u	072400	165	117	u	LCU	Lowercase u
v	073000	166	118	v	LCV	Lowercase v
w	073400	167	119	w	LCW	Lowercase w
x	074000	170	120	x	LCX	Lowercase x
y	074400	171	121	y	LCY	Lowercase y
z	075000	172	122	z	LCZ	Lowercase z
{	075400	173	123	{	LBR	Opening (left) brace
		076000	174	124
}	076400	175	125	}	RBR	Closing (right) brace
~	077000	176	126	~	TIL	Tilde
	077400	177	127	DEL	Delete. rubout

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ERROR MESSAGES¶

B.1 COMPILER MESSAGES¶

During compilation, diagnostic messages will be issued for any source text which either is, or may be, erroneous. These messages appear in the program listing after the statement to which they refer, and also on the background terminal.

They fall into three categories:

errors
warnings
extensions

Error messages are produced when the compiler cannot make a sensible interpretation of the program. Execution of these programs becomes impossible.

Warnings are given when there is a potential fault, but an object file is produced and execution may be possible.

Extension messages indicate where the program is using language features which are not part of the ANSI FORTRAN 77 standard. These messages are suppressed unless the STANDARD-CHECK compiler command is on.

Some messages may be preceded by some text in quotes. This may be either the name of some variables, or a part of the source program with a '?' inserted. This '?' will show where the error was detected and will usually be at or shortly after the item at fault.

The following list of the text of the error message texts is in alphabetical order:

Error Code	Description
-1 IN SUBSTRING	ANSI FORTRAN 77 must have positive values as indexes in substring values. ND FORTRAN uses -1 to mean stripping blanks from the string.

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1H ASSUMED¶

ANSI FORTRAN 77 requires the length of an H-format item to be explicitly stated.
ND FORTRAN allows 'HX' to mean '1HX'.

1X ASSUMED¶

ANSI FORTRAN 77 requires the length of the X format item to be explicitly stated.
ND FORTRAN allows 'X' to mean '1X'.

ALIGNMENT¶

A variable has been allocated to an address which cannot be supported, e.g., an INTEGER beginning at an odd-byte boundary on ND-100.

ALTERNATE RETURNS IN INTRINSIC FUNCTION¶

INTRINSIC functions cannot accept * return specifiers in their argument lists.

ALTERNATE RETURNS INVALID IN THIS PROGRAM UNIT¶

A RETURN statement was found that specified an alternate return expression when none of the entry points had * specifiers in their argument list.

ALTERNATE RETURNS ONLY ALLOWED IN SUBROUTINES¶

Alternate return specifiers are only valid in subroutines, not in functions.

APF-LIB WILL NOT BE USED BECAUSE OF THE ARRAY-INDEX-CHECK OPTION¶

Cannot have both the apf-lib option and the array-index-check option at the same time.

APT COMMON¶

The form of COMMON which is placed in the alternate page table on NORD-10/ND-100 is non-standard, and not available on ND-500.

ARGUMENT(S) CONVERTED¶

ANSI FORTRAN 77 allows only those actual arguments which match the corresponding dummy arguments without conversion. ND FORTRAN converts, where possible, the arguments to INTRINSIC and statement functions.

ARRAYS MUST HAVE THE SAME SHAPE¶

All arrays in an array-operation must have the same number of dimensions. All dimensions must be of equal size.

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'x' ASSUMED¶

x is a character which the compiler has assumed was omitted in the indicated position.

ASSUMED BECAUSE HAS 2 ARGUMENTS¶

The wrong generic or specific name was given for the number of arguments (i.e., ATAN instead of ATAN2).

ASSUMED-SIZE ARRAY USED AS LIST ITEM¶

Assumed-size array must not be used as a list item on input/output statements.

BRANCH INTO DO/IF NEST¶

The compiler has found an attempt to transfer control from outside to the inside of a DO loop or structured IF construct.

CANNOT BE CALLED¶

The indicated item cannot be invoked. It is neither external, INTRINSIC nor a statement function.

CANNOT BE DIMENSIONED¶

The named item cannot have dimensions (e.g., it may have been previously declared as external).

CANNOT BE PASSED AS AN ARGUMENT¶

The item cannot be used as an actual argument (e.g., MAX function).

CANNOT BE SAVED¶

The indicated item must not occur in a SAVE statement.

CANNOT BE USED IN A TYPE STATEMENT¶

A name has been explicitly given a type when this is not allowed (e.g., SUBROUTINE name).

CANNOT CONTAIN A LABEL¶

The indicated item is expected to have the value of a label in it (i.e., set by ASSIGN statement). The item must be an unsubscripted variable name of type INTEGER2 on NORD-10/ND-100 and INTEGER4 on ND-500.

CANNOT CONVERT¶

The requested conversion cannot be carried out (e.g., arithmetic to character).

CANNOT SELECT GENERIC ENTRY¶

There is no specific name for this generic entry which allows arguments of the required type.

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CHARACTER AND NON-CHARACTER EQUIVALENCED¶

ANSI FORTRAN 77 does not allow the mixing of character items with non-character items in an equivalence list.

CHARACTER IN APT COMMON¶

Character variables cannot be referenced via the APT on NORD-10/ND-100.

CHARACTER VARIABLE REFERENCED IN BOTH SIDES OF "="¶

It is illegal to refer to the same character variable in both source and destination part of an assignment statement.

COMMON BLOCKS EXCEED MEMORY¶

The total memory requirements of COMMON blocks exceeds 64K words (ND-100 only).

CONFLICTING POSITIONS¶

A variable has been allocated to two separate places by a combination of COMMON and EQUIVALENCE lists.

CONTROL VARIABLE NOT INTEGER¶

In an implied DO in a DATA statement, the loop control variable must be of type integer.

CONVERTED TO INTEGER¶

A non-integer arithmetic expression or constant was found where ANSI FORTRAN 77 requires an integer. ND FORTRAN allows the conversion.

DATA IN BLANK COMMON¶

Initializing variables in blank common by a DATA statement is an ND FORTRAN extension.

DATA IN COMMON¶

Initializing variables in COMMON with a DATA statement in a program unit, other than a BLOCK DATA subprogram, is an ND FORTRAN extension.

DATATYPE¶

The indicated data type is not in ANSI FORTRAN 77, but is a ND FORTRAN extension.

DATA STATEMENT IS ILLEGAL¶

Data statement must not occur in a recursive subprogram.

DECLARATION MISSING¶

If IMPLICIT OFF is used, every symbolic name requiring a data type must be declared in a Type statement.

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DIVIDE BY ZERO¶

In a constant expression, an attempt was made to divide by zero.

DO HAS ZERO STEP¶

In a DO loop, or an implied DO loop, the step value is zero.

DO/IF NESTING ERROR¶

DO loops or structured IFs are not properly nested.

DOUBLY DEFINED¶

An attempt was made to use a name for two conflicting purposes.

DOUBLY SAVED¶

A variable appears in more than one SAVE statement.

DUMMY NAME INSERTED¶

A name was expected. The compiler has created an internal name in order to continue processing.

EMBEDDED UNARY SIGN¶

ANSI FORTRAN 77 prohibits adjacent arithmetic operators, but ND FORTRAN allows it, e.g., A+-B.

ENTRY NOT ALLOWED IN DO/IF NEST¶

Entry statements cannot appear within DO loops or structured IF constructs.

ENTRY NOT SET BEFORE RETURN¶

In a function subprogram, an entry point has not been assigned. Invocation of this entry point might lead to an undefined value being returned.

ERRCODE NORMAL VARIABLE IN STANDARD PROGRAMS¶

If STANDARD CHECK is ON, ERRCODE is treated like a normal variable. Otherwise, it has a special meaning, see Section 9.1.7.

EXPRESSION MISSING¶

An expression was expected but not found.

EXTENDS COMMON NEGATIVELY¶

An EQUIVALENCE list required a variable or array to occupy storage preceding a COMMON block.

FORMAT¶

The indicated item is an ND FORTRAN extension.

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FORMAT ERROR¶

A FORMAT list is incorrectly specified, e.g., missing comma.

FORMAT LABEL TARGET OF BRANCH¶

Control cannot be transferred to labels on FORMAT statements.

HAS INVALID BOUNDS¶

The named variable cannot have the declared bounds. E.g., a local variable was given non-constant bounds, or the upper bound was less than the lower.

HAS INVALID LENGTH¶

The named variable cannot have the declared length. I.e., a local character string was declared with a non-constant length.

HOLLERITH CONSTANT¶

Hollerith constants are not part of the ANSI FORTRAN 77 standard. Appendix G describes how ND FORTRAN implements them. Character strings should be used instead of Hollerith constants wherever possible.

IGNORED IN BLOCK DATA¶

The indicated item is not valid in a BLOCK DATA subprogram, and has been ignored in order to continue processing.

ILLEGAL INDEX IN IMPLIED DO¶

Array-index error in implied DO.

IN A DIFFERENT COMMON BLOCK¶

In an EQUIVALENCE statement, two items in a single list are in different COMMON blocks.

INCLUDES NESTED TOO DEEPLY¶

The maximum depth of nesting for $INCLUDE commands is 5.

INCOMPLETE CHARACTER/HOLLERITH STRING¶

The end of a statement occurred before the end of a string. Possible causes are: missing quote, or wrong count before Hollerith H, or statement extends beyond column 72.

INEFFICIENT ACCESS MODE IN OPEN¶

This applies to the ND-500 only. The R, W, and RW access modes are very inefficient. If possible, DIRECT or SEQUENTIAL should be used.

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INTEGER INVALID OR OUT OF RANGE¶

An unacceptable integer constant has been found. The valid values depend on the context.

INTEGER MISSING, 1 ASSUMED¶

An integer was expected. The compiler assumes a value of 1 in order to continue processing.

INTERNAL FILES NEED A FORMAT¶

Using unformatted I/O on internal files is not allowed.

INTRINSIC FUNCTION¶

The named function is an ND FORTRAN extension.

INVALID AS A DUMMY ARGUMENT¶

The specified item cannot be a dummy argument.

INVALID AS FUNCTION/SUBROUTINE NAME¶

Cannot refer to a subprogram as both function and subroutine.

INVALID CHARACTER, STATEMENT IGNORED¶

A character is found which is not in the FORTRAN character set. Compilation continues with the next statement.

INVALID CHARACTER, SUBSTRING EXPRESSION¶

The character substring expression exceeds the maximum string length.

INVALID CONSTANT EXPRESSION¶

The expression cannot be computed at compile-time.

INVALID DIMENSION EXPRESSION¶

Dimension bounds must be integer expressions.

INVALID DO TERMINATION¶

The label specified in a DO statement was found with a statement that cannot terminate a DO loop.

INVALID IF EXPRESSION¶

The expression cannot be used in a Logical or Arithmetic IF. e.g., it may be of type CHARACTER.

INVALID IMPLICIT RANGE¶

The range in an implicit range is invalid (e.g., the second letter precedes the first).

INVALID IN CONSTANT LIST¶

The indicated item cannot be used as a constant in a DATA statement constant list.

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INVALID IN DATA LIST¶

The indicated item cannot be initialized in a DATA statement.

INVALID IN EQUIVALENCE LIST¶

The indicated item cannot share storage with any other item.

INVALID I/O LIST ITEM¶

Self-explanatory.

INVALID I/O OPTION¶

Self-explanatory.

INVALID ITERATION¶

In an implied DO loop in a DATA statement, the iteration count is negative or zero.

INVALID LABEL¶

A label was expected but not found.

INVALID LEFT SIDE OF ASSIGNMENT¶

Self-explanatory.

INVALID LOOP CONTROL¶

The control variable of a DO loop must be an integer, real, or double-precision variable.

INVALID OPERAND¶

The operand cannot be used with its operator.

INVALID SUBSCRIPT EXPRESSION¶

A subscript must be of type INTEGER.

LABEL DEFINED, BUT NOT REFERRED TO¶

The label is not referred to in other statements.

LABEL MISSING¶

A label was expected but not found.

LABEL NOT ALLOWED WITH THIS STATEMENT¶

Self-explanatory.

LABEL NOT ASSIGNED¶

The label must be assigned to an integer variable in a statement label assignment statement.

LABEL REFERS TO ITSELF¶

A potential endless loop was detected.

LABEL UNDEFINED¶

A label was used which did not appear in the label field of any statement.

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LABEL USED AS FORMAT¶

The label on an executable statement was found where a format label was expected.

LINE(S) ARE NON-BLANK BEYOND COL. 72¶

The indicated number of lines were found which had non-blank characters in columns beyond the 72nd, and these lines formed part of a statement or command. Comment lines which extend beyond column 72 are not included in this number.

LOCAL ARRAYS EXCEED MEMORY¶

The total memory requirements of local arrays exceeds 64K words (ND-100 only).

LOCAL DATA IGNORED IN RE-ENTRANT MODE¶

Local variables cannot be initialized by DATA statements in reentrant mode.

LOGICAL OPERATION ON INTEGERS¶

Self-explanatory.

MISPLACED '='¶

In an assignment statement, the left-hand side was not followed by an equals sign.

MISSING DIMENSION LIST¶

No dimensions were given in an array declarator.

MISSING 'END'¶

The end of file was found on the program test file when a program unit was still incomplete.

MISSING NAME, '#MAIN' ASSUMED¶

In order that the compiler may continue its processing, it has inserted the name #MAIN.

MISSING SPECIFICATION¶

An empty position was found in a list, e.g., 2 adjacent commas.

MISSING SUBSCRIPTS¶

An array name was used where it must be followed by a subscript list.

MISSING 'THEN'¶

The compiler assumes the keyword 'THEN' to be present, in order to continue processing the IF statement.

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MIXED LENGTH CHARACTER ENTRIES¶

ANSI FORTRAN 77 requires that all entry names in a function subprogram must be either of type non-character, or CHARACTER with the same length (or an *). ND FORTRAN removes this restriction completely.

MIXING CHARACTER AND NON-CHARACTER IN COMMON¶

ANSI FORTRAN 77 requires that all variables in a COMMON block be character, or that all are non-character.

MIXING DOUBLE PRECISION AND COMPLEX¶

ANSI FORTRAN 77 does not allow arithmetic operations to have one double precision and one complex operand. For the method of treatment by ND FORTRAN, see Section 4.4.

MORE THAN 6 CHARACTERS, 31 SIGNIFICANT¶

ANSI FORTRAN 77 restricts names to 6 characters. ND FORTRAN uses the first 31.

MORE THAN 7 DIMENSIONS¶

ANSI FORTRAN 77 allows no more than 7 dimensions for its arrays. ND FORTRAN can support more except within the Symbolic Debugger.

MULTIPLE ASSIGNMENT ILLEGAL FOR ARRAYS¶

Assignment to an array must not occur in a multiple assignment statement.

MULTI-DIMENSIONED ARRAYS NOT ALLOWED IN ARRAY-OPERATION¶

Only one-dimensional arrays are allowed in an array-operation.

NEITHER UNIT NOR FILE SPECIFIED¶

An INQUIRE statement must indicate the unit or file to be examined.

NO DO SPECIFICATION IN LIST¶

A parenthesised data list has no DO specification present.

NO MORE SPACE¶

The compiler has exhausted its work area. The program unit is too big to be compiled. Try subdividing it into subroutines, or moving DATA statements to a BLOCK DATA subprogram.

NON-STANDARD CHARACTER¶

ND FORTRAN allows an underscore character (_) in symbolic names.

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NON-STANDARD CONTINUATION¶

"&" has been used as a continuation mark.

NON-STANDARD EQUIVALENCING¶

Two data items share storage in a way which may make the execution of the program diverge from the ANSI FORTRAN 77 definition. E.g., REAL and INTEGER arrays overlapping on a ND-100.

NON-STANDARD EXPRESSION¶

Self-explanatory.

NON-STANDARD INTERNAL FILE OR FORMAT¶

Self-explanatory.

NON-STANDARD LABEL FIELD¶

ANSI FORTRAN 77 allows labels only in columns 1 to 5 inclusive.

NON-STANDARD REDEFINITION¶

A name is used, both as an external name or entry, and as a dummy argument in a statement function.

NOT A FUNCTION¶

Self-explanatory.

NOT A LOGICAL EXPRESSION¶

In a structured IF, the expressions controlling each of the ELSE IF's must be logical expressions.

NOT ALLOWED IN DIMENSION EXPRESSION¶

Self-explanatory.

NOT ALLOWED IN LOGICAL IF¶

The indicated statement cannot be part of a Logical IF statement.

NOT ENOUGH CONSTANTS¶

There were more items to be initialized in a DATA statement data list, than constants in the corresponding constant list.

NOT INTEGER CONSTANT EXPRESSION¶

Self-explanatory.

NOT INTRINSIC, EXTERNAL ASSUMED¶

The name is not one of the known INTRINSIC functions. It is assumed to be an external function in order to continue processing.

NOT SYMBOLIC CONSTANT¶

A name found where a constant expression should appear, was not a constant.

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NO UNIT SPECIFIER¶

All I/O statements must specify the unit on which they operate.

NULL STATEMENT¶

ANSI FORTRAN 77 does not allow completely empty statements. E.g., after a Logical IF.

OCTAL CONSTANT¶

Octal constants are an ND FORTRAN extension.

OPTION¶

The indicated option is an ND FORTRAN extension.

OUT OF DATA BEFORE CONSTANTS¶

In a DATA statement, the list of initialized items was shorter than the list of constants.

OUT OF RANGE¶

The value on the right side of the assignment operator is too large/small for the variable on the left side.

OVERLAPPING IMPLICIT RANGES¶

The same letter(s) occur in more than one range in implicit specifications.

PARENTHESES ASSUMED AROUND PARAMETERS¶

The PARAMETER statement should have its list of symbolic constant assignments enclosed in parentheses.

PRIORITY¶

Priority is valid only for ND FORTRAN programs.

REC AND END CONFLICT¶

The end-of-file indication can only occur in a direct access READ as an ND FORTRAN extension.

REC AND FMT = * CONFLICT¶

Free format I/O is only valid in SEQUENTIAL access READ and WRITE statements.

RECURSION¶

Recursion is valid only as an ND FORTRAN extension, and in reentrant mode.

RETURN IN PROGRAM¶

In ANSI FORTRAN 77, a program must terminate with a STOP statement or by reaching the END statement of the program subunit.

SAVE OF LOCALS NOT IMPLEMENTED IN REENTRANT MODE¶

Self-explanatory.

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SEMICOLON SEPARATOR¶

In ANSI FORTRAN 77, only one statement can be placed on a line. ND FORTRAN allows a semicolon character (;) to separate statements on a line.

SINGLE DIMENSIONING¶

The ability to refer to a multidimensional array by use of a single subscript is an ND FORTRAN extension.

SPECIFICATION AFTER DATA¶

ND FORTRAN allows DATA statements to appear before specification statements.

STATEMENT¶

The indicated statement is an ND FORTRAN extension.

STATEMENT HAS TOO MANY CONTINUATION LINES¶

ANSI FORTRAN 77 allows 19 continuation lines in one statement. The statement must be split.

SUBSTRING OF CONSTANT¶

Taking the substring of a symbolic constant is a ND FORTRAN extension.

SYMBOL NOT IN PARENTHESES¶

A symbolic constant being used to define a length of character items must be in parentheses in ANSI FORTRAN 77.

SYNTAX ERROR IN ARITHMETIC CONSTANT¶

Self-explanatory.

SYNTAX ERROR, REST OF STATEMENT IGNORED¶

A previous syntax error has been found. Processing is continued at the next statement.

TOO FEW ITEMS¶

In an EQUIVALENCE statement, each list must contain at least two items.

TOO LARGE LENGTH SPECIFIER¶

A character variable may have a length up to 2047 on ND-100 and 32767 on ND-500.

UNRECOGNISED OR MISPLACED STATEMENT¶

The statement is either badly formed (e.g., a misspelled keyword) or is out of sequence (e.g., a specification follows an executable statement).

VARIABLE NOT ASSIGNED¶

The variable is referred to before it is assigned.

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WRONG NUMBER OF ARGUMENTS¶

Self-explanatory.

WRONG USE OF ASSEMBLY NAME¶

The restrictions on use of symbolic names declared
in an ASSEMBLY statement have not been observed.

ZERO LENGTH STRING¶

Self-explanatory.

%COMMENT¶

ND FORTRAN allows comments to begin with a percent
(%) character.

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B.2 THE LOADER ERROR MESSAGES¶

These are described in the SINTRAN III Real Time Loader ND-60.051.

B.3 RUNTIME ERROR DIAGNOSTICS¶

The runtime error diagnostics are printed on the message output file, which is the user terminal (the SINTRAN error device for RT) in the format:

*** date time FORTRAN EXCEPTION : (nnn)
line error message
IN LINE l1 RETURN ADDRESS aaaaaa UNIT uu DEVICE dd

where:

Symbol	Description
nnn	is the octal error number
aaaaaa	is the address in octal of the executing program of the compiled statement in which the error has occurred.
l1	is the line number in decimal within the source program, of the compiled statement in which the error has occurred.
uu	is the FORTRAN unit number, decimal, on which the error has occurred.
dd	is the SINTRAN logical device number, octal, on which the error has occurred.

Note that on the ND-500, more information about traps and exceptions may be printed, see Appendix D.3.

If the error is serious the message JOB ABORTED is given and the control returns to the operating system.

If the error is not serious, ERRCODE is set to the value of the error code (and IOSTAT if applicable), and control returns to the FORTRAN program.

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Error Code Meaning (error text)¶

Decimal	Octal	Meaning (error text)
0	0	Not used
1	1	Not used
2	2	Bad file number
3	3	End of file
4	4	Card reader error (card read)
5	5	Device not reserved
6	6	Not used
7	7	Card reader error (card not read)
8	10	Not used
9	11	Not used
10	12	End of device (time-out)
11-16	13-20	Not used
17	21	Illegal character in parameter
18	22	No such page
19	23	Not decimal number
20	24	Not octal number
21	25	You are not authorized to do this
22	26	Directory not entered
23	27	Ambiguous directory name
24	30	No such device name
25	31	Ambiguous device name
26	32	Directory entered
27	33	No such logical unit
28	34	Unit occupied
29	35	Master block transfer error
30	36	Bit file transfer error
31	37	No more tracks available
32	40	Directory not on specified unit
33	41	Files opened on this directory
34	42	Main directory not last one released
35	43	No main directory
36	44	Too long parameter
37	45	Ambiguous user name
38	46	No such user name
39	47	No such user name in main directory
40	50	Attempt to create too many users
41	51	User already exists
42	52	User has files
43	53	User is entered
44	54	Not so much space unreserved in directory
45	55	Reserved space already used
46	56	No such file name
47	57	Ambiguous file name
48	60	Wrong password

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Error Code and Meaning¶

Decimal	Octal	Meaning (error text)
49	61	User already entered
50	62	No user entered
51	63	Friend already exists
52	64	No such friend
53	65	Attempt to create too many friends
54	66	Attempt to create yourself as friend
55	67	Continuous space not available
56	70	Not directory access
57	71	Space not available to expand file
58	72	Space already allocated
59	73	No space in default directories
60	74	No such file version
61	75	No more pages available for this user
62	76	File already exists
63	77	Attempt to create too many files
64	100	Outside device limits
65	101	No previous versions
66	102	File not continuous
67	103	File type already defined
68	104	No such access code
69	105	File already opened
70	106	Not write access
71	107	Attempt to open too many files
72	110	Not write and append access
73	111	Not read access
74	112	Not read, write and common access
75	113	Not read and write access
76	114	Not read and common access
77	115	File reserved by another user
78	116	File already opened for write
79	117	No such user index
80	120	Not append access
81	121	Attempt to open too many mass storage files
82	122	Attempt to open too many files
83	123	Not opened for sequential write
84	124	Not opened for sequential read
85	125	Not opened for random write
86	126	Not opened for random read
87	127	File number out of range
88	130	File number already used
89	131	No more buffer space
90	132	No file opened with this number
91	133	Not mass storage file
92	134	File used for write

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Decimal	Octal	Meaning (error text)
93	135	File used for read
94	136	File only opened for sequential read or write
95	137	No scratch file opened
96	140	File not reserved by you
97	141	Transfer error
98	142	Reserved by RT program
99	143	No such block
100	144	Source and destination equal
101	145	Illegal on tape device
102	146	End of tape
103	147	Tape already in use
104	150	Not random access on tape files
105	151	Not last file on tape
106	152	Not tape device
107	153	Illegal address reference in monitor call
108	154	Not last record on tape
109	155	File already opened by another user
110	156	File already opened for write by another user
111	157	Missing parameter
112	160	Two pages must be left unreserved
113	161	No answer from remote computer
114	162	Device cannot be reserved
115	163	Overflow in read
116	164	DMA error
117	165	Bad datablock
118	166	Control/modus word error
119	167	Parity error
120	170	LCR error
121	171	Device error (read-last-status to get status)
122	172	No device buffer available
123	173	Illegal mass storage unit number
124	174	Illegal parameter
125	175	Write-protect violation
126	176	Error detected by read after write
127	177	No EOF mark found
128	200	Cassette not in position
129	201	Illegal function code
130	202	Time-out (no datablock found)
131	203	Paper fault
132	204	Device not ready
133	205	Device already reserved
134	206	Not peripheral file
135	207	No such queue entry
136	210	No so much space left

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Appendix B¶

Error Code	Meaning (error text)

Decimal | Octal

137 | 211 | No spooling for this device
138 | 212 | No such queue
139 | 213 | Queue empty
140 | 214 | Queue full
141 | 215 | Not last used by you
142 | 216 | No such channel name
143 | 217 | No remote connection
144 | 220 | Illegal channel
145 | 221 | Channel already reserved on remote computer
146 | 222 | No remote file processor
147 | 223 | Formatting error
148 | 224 | Incompatible device sizes
149 | 225 | Remote Processor not available
150 | 226 | Tape format error
151 | 227 | Block count error
152 | 230 | Volume not on specified unit
153 | 231 | Not deleted record
154 | 232 | Device error
155 | 233 | Error in object entry
156 | 234 | Odd number of bytes (right byte in last word insignificant) 157-256 234-400 Not used

257 | 401 | Fatal formatting system error.
| | This is a system error due to software or hardware errors.

258 | 402 | Too low parentheses level in format.
| | A maximum of 5 levels is permitted.

259 | 403 | Illegal character in format

260 | 404 | Illegal termination of format

261 | 405 | Output record size exceeded.
| | A maximum of 136 characters is permitted.

262 | 406 | Format requires greater input record

264 | 410 | Input record size exceeded.
| | A maximum of 136 characters is permitted.

265 | 411 | Backspace illegal

266 | 412 | Bad character on input.
| | The input field is ignored and the result will be zero.

267 | 413 | Real overflow on input.
| | The result will be 1.0E76.

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Appendix B¶

Error Code	Meaning (error text)
Decimal	Octal
268	414
269	415
270	416
271	417
272	420
273	421
274	422
275	424
277	425
278	426
279	427
280	430
281	431
282	432
283	433
284	434
285	435
286	436
287	437
288	440
289	441
294	446
295	447
296	450
	290-293
	297-301

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Appendix B¶

Error Code	Meaning (error text)
Decimal	Octal
297-301	451-455
302	456
303	457

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Appendix C¶

MONITOR CALLS¶

C.1 INTRODUCTION TO USING MONITOR CALLS¶

If a Fortran program wishes to communicate directly with the SINTRAN operating system, Monitor Calls are provided for this purpose. The FORTRAN language and runtime system has a variety of facilities, such as I/O statements for accessing files or handling peripheral devices. However, some situations require direct communication between a program and the SINTRAN operating system. In general, this means that the program is requesting a particular service be carried out, or that some specific item of information is required.

The Monitor Calls may be called by using the statements:

MONITOR CALL(number, par-1, ..., par-n)

or

MONITOR CALL('name', par-1, ..., par-n)

where

number	is the Monitor Call number
'name'	is the name of the Monitor Call.

Further explanation of each Monitor Call is given in the manual SINTRAN III Monitor Calls ND-60.228.1.

Some Monitor Call routines are provided in the FORTRAN library. These may be called from a FORTRAN program as either a subroutine or a function subprogram. The main difference is that in using a monitor call as a function, a value is returned indicating the result of carrying out the request.

Most monitor calls may be used as a function or a subroutine. However, some may only be used as a function since the function value is the information which was requested, e.g., the monitor call TUSED returns the CPU time used by a terminal since a logon.

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If a function returns a status code, it is strongly recommended that this status is tested. If a monitor call is called as a subroutine, then status, e.g., error conditions, must be detected in a different way to functions. The system variable ERRCODE, which is an ND FORTRAN extension, may be used with many of the monitor calls (both functions and subroutines) to detect errors. If ERRCODE is used to detect errors from monitor calls, the program must not be compiled in STANDARD-CHECK ON modus.

Example - a monitor call used as a subroutine¶

For example, to set the system time and date, use the monitor call CLOCK (MON 113) as a subroutine:

C DECLARATIONS¶

INTEGER PARAMS(7)
INTEGER BUNITS, SECONDS, MINUTES, HOURS, DAYOFMTH, MONTH, YEAR

C SET UP SOME CONVENIENT VARIABLE NAMES FOR THE TIME AND DATE¶

EQUIVALENCE (PARAMS(1), BUNITS), (PARAMS(2), SECONDS)
EQUIVALENCE (PARAMS(3), MINUTES), (PARAMS(4), HOURS)
EQUIVALENCE (PARAMS(5), DAYOFMTH), (PARAMS(6), MONTH)
EQUIVALENCE (PARAMS(7), YEAR)

C USE MONITOR CALL TO GET SYSTEM TIME AND DATE¶

CALL CLOCK(PARAMS)

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Example - a monitor call used as a function¶

To read information directly from a device, use the monitor call INCH as a function:

C DECLARATIONS (INCLUDING THE MONITOR CALL TO BE USED
C AS FUNCTION)
C
INTEGER JNUNIT,ONECHAR
INTEGER INCH

C
C READ ONE CHARACTER FROM THE DEVICE WHICH IS CONNECTED
C TO THE FORTRAN UNIT NUMBER IN JNUNIT
C
ONECHAR=INCH(JNUNIT)

C
C CHECK THE SYSTEM VARIABLE, ERRCODE, TO SEE IF ALL WENT WELL
C
IF(ERRCODE .NE. 0) GO TO 10

C
C CONTINUE PROCESSING
C
...

C
C ERROR OCCURRED, TERMINATE
C
10 CONTINUE
STOP

Note:

The system variable, ERRCODE, contains a value upon return from many monitor calls. The value returned indicates that the service requested has been successfully carried out, or whether an error or some unusual condition has arisen.
If a monitor call is used as a function, the function name must be declared as a specific data type, to define for the compiler the precise way that this variable name will be used.

All monitor calls, which may be used in FORTRAN, are listed in the Table of Monitor Calls, in section C.3. For each monitor call, the table describes the name which must be used, if the monitor call should be used as a function only, the number of parameters and their corresponding data types, and whether ERRCODE contains a value upon return.

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The complete definition of all available monitor calls is in the SINTRAN Reference Manual, ND-60.128. This includes an explanation of the meaning of each parameter and rules about the use of each monitor call.

The monitor calls available to FORTRAN programs, i.e., supplied in the FORTRAN library, are limited to those described in section C.3, which does not include all those available from the SINTRAN operating system. Note that the name to be used for a specific monitor call in FORTRAN could be different from the name used in the SINTRAN Reference Manual. The example above shows how the monitor call INCH is used; in the SINTRAN Reference Manual this monitor call is named INBT. The table in section C.3 has the names to be used in FORTRAN.

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Appendix C

C.2 COMMONLY USED MONITOR CALLS¶

This section illustrates some of the more commonly used monitor calls. Each monitor call which has been selected, has a brief explanation of its function and an example of the way it can be called from a FORTRAN program.

The monitor calls are categorized into the same groups as in the SINTRAN Reference Manual, ND-60.128, Chapter 4.

Summary of the Monitor Calls in this Section¶

Alphabetical order	Numerical order
ABORT 105 (C.2.1)	INCH (C.2.2)
BRKM 4 (C.2.3)	OUTCH (C.2.2)
CLOCK 113 (C.2.1)	ECHOM (C.2.3)
ECHOM 3 (C.2.3)	BRKM (C.2.3)
COMMND 70 (C.2.1)	TIME (C.2.1)
ERMSG 64 (C.2.6)	MSG (C.2.3)
HOLD 104 (C.2.1)	ERMSG (C.2.6)
INCH 1 (C.2.2)	ISIZE (C.2.3)
ISIZE 66 (C.2.3)	COMMND (C.2.1)
MAGTP 144 (C.2.3)	SMAXD (C.2.4)
MSG 32 (C.2.3)	REABT (C.2.4)
OUTCH 2 (C.2.2)	SETBS (C.2.4)
OUTST 162 (C.2.2)	RT (C.2.1)
REABT 75 (C.2.4)	HOLD (C.2.1)
RFILE 117 (C.2.5)	ABORT (C.2.1)
RSIO 143 (C.2.5)	CLOCK (C.2.1)
RT 100 (C.2.1)	TUSED (C.2.1)
RTWT 135 (C.2.1)	RFILE (C.2.5)
SETBS 76 (C.2.4)	WFILE (C.2.5)
SMAX 73 (C.2.4)	WAITF (C.2.5)
TIME 11 (C.2.1)	PTWTF (C.2.1)
TUSED 114 (C.2.1)	WHDEV (C.2.2)
WAITF 121 (C.2.5)	RSIOV (C.2.5)
WFILE 120 (C.2.5)	MAGTP (C.2.3)
WHDEV 140 (C.2.2)	OUTST (C.2.2)

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C.2.1 PROGRAM ADMINISTRATOR¶

TIME - MON 11¶

Read the current time, in basic time units, i.e., 20 milliseconds per unit or some preset value, as held by the operating system.

C GET THE CURRENT TIME IN INTERNAL UNITS
C
      INTEGER*4 TIME,CURRENTTIME,DUMMY
C
      CURRENTTIME=TIME(DUMMY)

COMND - MON 70¶

Transfer the contents of a string to the SINTRAN command processor's buffer, and the string will be executed by SINTRAN.

C
C REQUEST SINTRAN TO EXECUTE A COMMAND TO CREATE A FILE
C DURING EXECUTION OF THIS PROGRAM
C
      CHARACTER*20 COMMAND
C
C ON THE ND-100, THE CHARACTER STRING MUST START ON A WORD
C BOUNDARY. EQUIVALENCE WITH AN INTEGER VARIABLE WILL
C ACCOMPLISH THIS.
C
      INTEGER I
      EQUIVALENCE(COMMAND,I)
C
C SET THE CONTENTS OF THE STRING VARIABLE TO A SINTRAN COMMAND.
C NOTE THE CHARACTER STRING DOES NOT BEGIN WITH AN @ CHARACTER.
C FURTHERMORE, THE STRING MUST BE TERMINATED BY AN APOSTROPHE.
C
      COMMAND='CREATE-FILE A-NEW-FILE:SYMB 100'''
C
C REQUEST SINTRAN TO EXECUTE THE CONTENTS OF "COMMAND"
C
      CALL COMND(COMMAND)

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Appendix C¶

RT - MON 100¶

Put an entry in execution queue, to request execution of an RT program.

C
C PUT REQUEST FOR EXECUTION OF THE RT PROGRAM IN THE EXECUTION
C QUEUE
C
EXTERNAL RTJOB
C
CALL RT(RTJOB)

HOLD - MON 104¶

Set the calling program in a waiting state for a specified period. The program will continue execution after return from the call to HOLD.

C
C WAIT FOR 30 SECONDS, THEN OUTPUT A MESSAGE, INCLUDING A COUNT,
C ONCE EVERY TEN TIME UNITS
C
INTEGER TERMINAL, COUNT, TUNITS, SECONDS
INTEGER LONGWAIT, MSGWAIT, MSGLIMIT
C
C INITIALIZE TERMINAL LOGICAL UNIT
C
DATA TERMINAL/1/
C
C INITIALIZE TIME UNIT INDICATORS
C
DATA TUNITS/1/, SECONDS/2/
C
C INITIALIZE WAIT TIMES
C
DATA LONGWAIT/30/, MSGWAIT/10/
C
C PUT PROGRAM IN A WAIT STATE FOR 30 SECONDS
C
CALL HOLD(LONGWAIT, SECONDS)
C
C OUTPUT SOME MESSAGES WITH A COUNT EVERY TENTH BASIC TIME UNIT
DO 10 COUNT = 1, MSGLIMIT
WRITE(TERMINAL, 100) COUNT
100 FORMAT(X, 'Still alive in here! Message number: ', I5)
CALL HOLD(MSGWAIT, TUNITS)
C
C DO SOME OTHER PROCESSING
C
10 CONTINUE

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ABORT - MON 105¶

Stop an RT program by setting it in a passive state. The program will be removed from the time or execution queue, all resources will be released and further periodic execution will be prevented.

C STOP AN RT PROGRAM

EXTERNAL COLLECT

CALL ABORT(COLLECT)

CLOCK - MON 113¶

Get the current time and date from the operating system.

C GET THE SYSTEM TIME AND DATE AND PRINT IN A PLEASANT FORMAT

INTEGER PARAMS(7)

C GET TIME AND DATE

CALL CLOCK(PARAMS)

C PRINT THE TIME AND DATE IN A USEFUL FORMAT

WRITE(PRINTFILE,100) (PARAMS(I), I=2,7)
100 FORMAT(X,'The time is : ',I2,':',I2,':',I2,/, 
          X,'The date is : ',I2,'/',I2,'/',I4)

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TUSED - MON 114¶

Get the CPU time used by a terminal since the last logon, or since the last batch job was started.

C
C COMPUTE THE TIME REQUIRED TO COMPLETE EXECUTION OF A LOOP
C
    INTEGER*4 CPUSTART, CPUFINISH, LOOPTIME, TUSED

C
C GET CPU TIME PRIOR TO THE LOOP
    CPUSTART=TUSED(DUMMY)

C
C THE LOOP WE WANT TO TIME
C
    DO

C
C THE LOOP DOING SOMETHING
    ENDDO

C
C THE LOOP HAS FINISHED, COMPUTE HOW LONG IT TOOK.
C
    CPUFINISH=TUSED(DUMMY)
    LOOPTIME=CPUFINISH-CPUSTART

RTWT - MON 135¶

Set the RT program issuing the call in a wait state until it is restarted, e.g., by another program calling RT (MON 100). The program which issued the RTWT call will restart at the statement immediately following the RTWT call.

    PROGRAM HOPE

C
C SET THIS PROGRAM IN A WAIT STATE, HOPING THAT IT GETS
C RESTARTED SOONER OR LATER
C
    INTEGER TERMINAL

C
C INITIALIZE THE TERMINAL LOGICAL UNIT NUMBER
    DATA TERMINAL/1/

C
C TAKE A REST FOR A WHILE
C
    CALL RTWT

C
C AFTER BEING RESTARTED, CARRY ON FROM HERE. TELL THE USER.
C
    WRITE(TERMINAL,*)'Hurray, we are off again!'

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C.2.2 RETRIEVING/CHANGING DEVICE INFORMATION¶

INCH - MON 1¶

Read one byte from a device. If the device is a data link or word-oriented internal device, read one word.

C  READ ONE BYTE INTO THE VARIABLE ICHAR FROM A DEVICE. THE
C  DEVICE MUST HAVE BEEN OPENED AND ITS FORTRAN UNIT NUMBER
C  STORED IN THE VARIABLE IFNUM, OR A SINTRAN LDN MAY BE USED.
C

   ICHAR=INCH(IFNUM)
C  IF NOT SUCCESSFUL, PRINT A FILE SYSTEM ERROR MESSAGE
C

   IF (ERRCODE .NE. 0) CALL ERMSG(ERRCODE)

OUTCH - MON 2¶

Write one byte to a device or to a file. If the device is a data link or word-oriented internal device, write one word.

C  WRITE ONE BYTE FROM ICHAR TO A FILE. THE FILE MUST HAVE
C  BEEN OPENED AND ITS FORTRAN UNIT NUMBER STORED IN THE
C  VARIABLE IFNUM, OR A SINTRAN LDN MAY BE USED.
C

   CALL OUTCH(IFNUM,ICHAR)
C
C  IF NOT SUCCESSFUL, PRINT A FILE SYSTEM ERROR MESSAGE
C

   IF (ERRCODE .NE. 0) CALL ERMSG(ERRCODE)

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Appendix C¶

WHDEV - MON 140¶

Check whether a logical device is reserved.

C  
C CHECK WHETHER A LOGICAL DEVICE IS FREE FOR OUTPUT,  
C SO THAT THIS PROGRAM CAN CONTINUE PROCESSING.  
C  
INTEGER TERMINAL,LOGDEVICE,OUTPUT,FREE  
INTEGER RTDESC, NHDEV  

C  
C INITIALIZE TERMINAL LOGICAL UNIT AND LOGICAL DEVICE NUMBER  
C  
DATA TERMINAL/1/,LOGDEVICE/10/  

C  
C INITIALIZE PARAMETER VALUES  
C  
DATA OUTPUT/1/,FREE/0/  

C  
C GET THE DEVICE INFORMATION  
C  
RTDESC=WHDEV(LOGDEVICE,OUTPUT)  

C  
C CARRY ON IF THE DEVICE IF FREE FOR OUTPUT  
C  
IF(RTDESC .NE. FREE) THEN  
WRITE(TERMINAL,*) 'Sorry, device already reserved'  
STOP  
ENDIF

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Appendix C¶

OUTST - MON 162¶

Write a string of characters to a peripheral device.

C
C WRITE A MESSAGE TO THE USER'S TERMINAL
C
INTEGER IMSG,LENGTH,LOGUNIT
CHARACTER*50 MESSAGE

C
C EQUIVALENCE TO AN INTEGER SO IT STARTS ON A WORD BOUNDARY
C
EQUIVALENCE (IMSG,MESSAGE)

C
C INITIALIZE THE MESSAGE AND ITS LENGTH IN BYTES
C
DATA MESSAGE/'Hello from your friendly program'/
DATA LENGTH/50/

C
C INITIALIZE THE LOGICAL UNIT NUMBER FOR THE TERMINAL
C
DATA LOGUNIT/1/

C
C WRITE THE MESSAGE
C
MONSTATUS=OUTST(LOGUNIT,MESSAGE,LENGTH)
C CHECK THAT ALL IS WELL
IF(MONSTATUS .NE. 0) CALL ERMSG(MONSTATUS)

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Appendix C¶

C.2.3 DEVICE HANDLING¶

ECHOM - MON 3

Set echo strategy for a terminal.

C  SET THE ECHO STRATEGY TO NOT ECHO ANY CHARACTERS, I.E.  
C  USEFUL  
C  FOR ENTERING A PASSWORD, THEN RESET THE ECHO STRATEGY.  
C  
   INTEGER TERMINAL,SUPPRESS,NORMAL  

C  
C  INITIALIZE TERMINAL LOGICAL UNIT, AND ECHO STRATEGIES  
C  
   DATA TERMINAL/1/,SUPPRESS/-1/,NORMAL/1/  

C  
C  SET NO ECHO FOR PASSWORD PROCESSING  
C  
   CALL ECHOM(TERMINAL,SUPPRESS)  

C  
C  GET USER PASSWORD, WITH APPROPRIATE CHECKS  
C  
   ...  

C  
C  RESET TO ECHO ALL CHARACTERS ON THE TERMINAL  
C  
   CALL ECHOM(TERMINAL,NORMAL)

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Appendix C

BRKM - MON 4¶

Set a specific break strategy for a terminal.

C
C SET THE BREAK STRATEGY SO THAT THE USER PROGRAM MAY EXAMINE
C EVERY CHARACTER, AS IT IS TYPED ON THE USER'S TERMINAL.
C
      INTEGER TERMINAL,ALLCHARS
C
C INITIALIZE TERMINAL LOGICAL UNIT NUMBER
C
      DATA TERMINAL/1/
C
C SET ARGUMENT VALUE FOR BREAK ON ALL CHARACTERS
C
      DATA ALLCHARS /0/
C
C SET BREAK ON ALL CHARACTERS, FOR THE USER'S TERMINAL
C
      CALL BRKM(TERMINAL,ALLCHARS)

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Appendix C¶

MSG - MON 32¶

Write a character string to the user's terminal.

SEND A MESSAGE TO THE TERMINAL¶

CHARACTER*80 MESSAGE

On the ND-100, the character string must start on a word boundary. Equivalence with an integer variable will accomplish this.

INTEGER I
EQUIVALENCE(MESSAGE,I)

INITIALIZE THE MESSAGE TEXT¶

DATA MESSAGE/'Dear user, have a nice day'/

SEND THE MESSAGE¶

CALL MSG(MESSAGE)

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Appendix C¶

ISIZE - MON 66¶

Get the number of bytes, currently in the terminal input buffer, i.e., those characters which have not yet been read by the user program.

C A TERMINAL IS BEING USED FOR OPERATOR INPUT AND OUTPUT OF
C MESSAGES. CHECK WHETHER THE OPERATOR HAS BEGUN TYPING 
C SOMETHING, PRIOR TO OUTPUT OF A MESSAGE TO THE TERMINAL.
C

INTEGER TERMINAL
INTEGER INCHARS

C
C INITIALIZE THE TERMINAL LOGICAL UNIT NUMBER
C

DATA TERMINAL/1/

C
C CHECK IF OPERATOR HAS BEGUN TYPING ON THE TERMINAL
C

INCHARS=ISIZE(TERMINAL)
IF(INCHARS .GT. 0) GO TO 10

C
C NO, OUTPUT A MESSAGE TO THE TERMINAL
C

WRITE(TERMINAL,*) 'Dear user, are you still there?'

C

...
C
C OPERATOR HAS BEGUN TYPING, PROCESS HIS INPUT BEFORE
C PRINTING THE MESSAGE ON THE TERMINAL
C
10 CONTINUE

MAGTP - MON 144¶

This monitor call reads from, writes to, or performs a variety of control functions for magnetic tape devices. It may also be used with other devices with similar characteristics to magnetic tape devices, e.g., Versatec printer/plotter or floppy disk.

C
C EXAMPLES OF A MAGNETIC TAPE DEVICE, READ AND REWIND OPERATION
C

INTEGER MAGTP, DATA(100), LOGUNIT
INTEGER READREC, REWIND
INTEGER STATUS, LENGTH, WORDSREAD, DUMMY

C
C INITIALIZE THE LOGICAL UNIT NUMBER AND REQUIRED FUNCTIONS
C

DATA LOGUNIT/32/
DATA READREC/0/, REWIND/13B/

C
C READ A RECORD, 50 WORDS SAY
C

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Appendix C¶

LENGTH=50
STATUS=MAGTP(READREC,DATA,LOGUNIT,LENGTH,WORDSREAD)

If all is not well, exit to error processing

IF(STATUS .NE. 0) GO TO ...

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C.2.4 RETRIEVING/CHANGING FILE SYSTEM INFORMATION¶

SMAX - MON 73 and REABT - MON - 75

SMAX sets the value of the maximum byte pointer of a file.

REABT reads the byte pointer as it would be used for the next sequential access of a mass storage file.

C AFTER WRITING SOME RECORDS TO A FILE, UPDATE THE MAXIMUM BYTE POINTER. C

INTEGER SMAX, REABT
INTEGER*4 BYTEPOINTER, MAXBYTEPOINTER
INTEGER LOGUNIT

C INITIALIZE THE LOGICAL UNIT NUMBER C

DATA LOGUNIT/10/

C OPEN THE FILE C

OPEN(LOGUNIT, FILE='MY-DATA-FILE', ACCESS='SPECIAL', ....)

C WRITE SOME RECORDS CONTAINING DATA TO THE FILE C

...

C GET THE VALUE OF THE BYTE POINTER FOR THE FILE C

CALL REABT(LOGUNIT, BYTEPOINTER)

C CHECK THAT ALL IS WELL C

IF(ERRCODE .NE. 0) CALL ERMSG(ERRCODE)

C UPDATE THE VALUE OF THE MAXIMUM BYTE POINTER FOR THE FILE C

MAXBYTEPOINTER = BYTEPOINTER - 1
CALL SMAX(LOGUNIT, MAXBYTEPOINTER)

C CHECK THAT ALL IS WELL C

IF(ERRCODE .NE. 0) CALL ERMSG(ERRCODE)

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Appendix C¶

SETBS - MON 76¶

Set the block size of a file to a specific value temporarily (until the file is closed), which will then be used for random read and write operations.

In the example below, the FACTOR= specifier of the OPEN statement is set to 4 which is the default value for operation on the ND-500. This program can be used on the ND-100 without any changes; but note that the default value is 2 for the ND-100.

The FACTOR= specifier, in the OPEN statement, might be set to 1 which means that the monitor calls, RFILE, WFILE, SETBS and MAGTP will use block size in bytes, rather than using the default word sizes relevant to either machine. Note that an even number of bytes should be used.

C
C SET THE BLOCK SIZE TO 4096 BYTES. THE DEFAULT BLOCK SIZE WHEN
C THE FILE IS OPENED IS 512 BYTES (256 WORDS ON THE ND-100).
C
     INTEGER LOGUNIT, FAC500, TBSBYTES, TBSUNITS
C
C INITIALIZE THE LOGICAL UNIT NUMBER
C
     DATA LOGUNIT/10/
C
C INITIALIZE TEMPORARY BLOCK SIZE, IN BYTES
C
     DATA TBSBYTES/4096/
C
C INITIALIZE VALUE TO DEFAULT FOR THE ND-500
C
     DATA FAC500/4/
C
C OPEN THE FILE, USE FACTOR= TO SET DEFAULT VALUE FOR ND-500
C
     OPEN(LOGUNIT,FACTOR=FAC500,ACCESS='SPECIAL',....)
C
C CHANGE FROM THE DEFAULT BLOCK SIZE TO 4096 BYTES.
C THIS BLOCK SIZE WILL BE USED UNTIL THE FILE IS CLOSED,
C OR ANOTHER SETBS CALL IS MADE.
C
     TBSUNITS=TBSBYTES/FAC500
     CALL SETBS(LOGUNIT,TBSUNITS)
C
C CHECK THAT ALL IS WELL
C
     IF(ERRCODE .NE. 0) CALL ERMSG(ERRCODE)

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C.2.5 FILE OPERATIONS¶

RFILE - MON 117 and WFILE - MON 120

Access a file randomly and read or write a specified number of words to or from a file block.

C
C READ A BLOCK OF DATA, 2048 BYTES, RANDOMLY FROM ONE FILE AND
C WRITE IT RANDOMLY TO ANOTHER FILE. THEN READ THE NEXT RECORD
C FROM THE INPUT FILE.
C THE FACTOR= PARAMETER IN THE OPEN STATEMENT IS SET TO THE
C DEFAULT VALUE FOR THE ND-100, I.E. 2 BYTES.
C
     INTEGER INUNIT, OUTUNIT, FAC100, READNEXT
     INTEGER DATA(1024), LENGTH, BLOCKNUM
     INTEGER IOCOMPLETE
C
C INITIALIZE THE LOGICAL UNIT NUMBERS
C
     DATA INUNIT/10/, OUTUNIT/12/
C
C INITIALIZE DEFAULT VALUE FOR THE ND-100 IN OPEN STATEMENT
C
     DATA FAC100/2/
C
C SET BLOCK NUMBER TO "READ NEXT BLOCK"
C
     DATA READNEXT/-1/
C
C SET ARGUMENT TO WAIT UNTIL I/O OPERATION COMPLETE
C
     DATA IOCOMPLETE/0/
C
C INITIALIZE LENGTH OF THE DATA AREA FOR RECORDS, IN WORDS
C
     DATA LENGTH/1024/
C
C OPEN THE FILES, USE FACTOR= SETTING FOR WORD SIZE ON ND-100
C
     OPEN(INUNIT,...,FACTOR=FAC100,ACCESS='SPECIAL'...)
     OPEN(OUTUNIT,...,FACTOR=FAC100,ACCESS='SPECIAL'...)
C
C READ BLOCK RANDOMLY (FIFTH BLOCK) FROM THE INPUT FILE
C
     BLOCKNUM=4
     CALL RFILE(INUNIT,IOCOMPLETE,DATA,BLOCKNUM,LENGTH)
C
C CHECK THAT ALL IS WELL
C
     IF(ERRCODE .NE. 0) CALL ERMSGS(ERRCODE)
C
C WRITE THE BLOCK RANDOMLY (SECOND BLOCK) TO THE OUTPUT FILE
C
     BLOCKNUM=1
     CALL WFILE(OUTUNIT,IOCOMPLETE,DATA,BLOCKNUM,LENGTH)

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C CHECK THAT ALL IS WELL
C
     IF(ERRCODE .NE. 0) CALL ERMSG(ERRCODE)

C NOW DO A "READ NEXT BLOCK" OPERATION FROM THE INPUT FILE
C I.E., THE SIXTH BLOCK
C
     CALL RFILE(IUNINT,IOCOMPLETE,DATA,READNEXT,LENGTH)

C CHECK THAT ALL IS WELL
C
     IF(ERRCODE .NE. 0) CALL ERMSG(ERRCODE)

RSIO - MON 143¶

Find out the execution mode of the calling program, user number, and input and output file numbers.

C OUTPUT A MESSAGE ONLY IF THE PROGRAM IS IN INTERACTIVE MODE,
C AND THE OUTPUT FILE IS A CHARACTER DEVICE.
C
     INTEGER TERMINAL,INTERACTIVE,OCUPPER
     INTEGER EXMODE,INDEVICE,OUTDEVICE,INXUSER

C INITIALIZE THE LOGICAL UNIT NUMBER
C
     DATA TERMINAL/1/

C INITIALIZE VALUE FOR INTERACTIVE MODE AND LOWER LIMIT DEVICE
C NUMBER FOR CHARACTER DEVICES
C
     DATA INTERACTIVE/0/,OCUPPER/63/

C REQUEST EXECUTION MODE ETC.
C
     CALL RSIO(EXMODE,INDEVICE,OUTDEVICE,INXUSER)

C OUTPUT MESSAGE IF THINGS ARE AS WE WISH
C
     IF(EXMODE .EQ. INTERACTIVE .AND.
     1    OUTDEVICE .LE. OCUPPER) THEN
          WRITE(TERMINAL,*) 'Hello there user'
     ENDIF

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WAITF - MON 121¶

Check the state of a mass storage transfer, or whether a transfer initiated by RFILE or WFILE is complete.

C

C WAIT UNTIL AN I/O TRANSFER IS COMPLETE, BEFORE CONTINUING
C PROCESSING
C

INTEGER LOGUNIT, IONOWAIT, IOCOMPLETE  
INTEGER IOSTATUS

C
C INITIALIZE THE LOGICAL UNIT NUMBER
C

DATA LOGUNIT/10/

C
C SET ARGUMENT VALUES FOR DESIRED ACTIONS
C

DATA IONOWAIT/1/, IOCOMPLETE/0/

C
C OPEN MASS STORAGE FILE
C

OPEN(LOGUNIT, ACCESS='SPECIAL', FILE=...)

C
C READ A RECORD FROM THE FILE
C

CALL RFILE(LOGUNIT, IONOWAIT, ...)

C
C PROGRAM CAN CONTINUE PROCESSING HERE; SOME CALCULATIONS
C
...
C SET PROGRAM IN A WAIT STATE UNTIL I/O HAS FINISHED
C

IOSTATUS=WAITF(LOGUNIT, IOCOMPLETE)

C
C CHECK THAT ALL IS WELL
C

IF(IOSTATUS .GT. 0) CALL ERMSG(ERRCODE)

C
C ALL IS WELL, I/O TRANSFER IS FINISHED

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Appendix C¶

C.2.6 ERROR HANDLING¶

ERMSG - MON 64¶

Print the File System error message corresponding to the value in the argument. This is often used to print an error message to explain the value of ERRCODE which has been set by an earlier monitor call.

C
C PRINT AN APPROPRIATE FILE SYSTEM ERROR MESSAGE
C NOTE THAT ERRCODE VALUE OF ZERO USUALLY MEANS ALL IS WELL
C
    IF(ERRCODE .NE. 0) CALL ERMSG(ERRCODE)

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ND-100 AND ND-500 MONITOR CALLS¶

Note: in the following table, "integer" in the column "data type" means default integer type: integer2 on the ND-100, and integer4 on the ND-500.

Name	MON	Fun or Sub	arguments/return	ERRCODE set
		number, purpose	data type	comments
LEAVE	0	F/S	none	no return
INCH	1	F	1. input unit	integer
see			return value	integer
note 2
OUTCH	2	F	1. output unit	integer
see			2. output character	integer
note 2			return value	integer
ECHOM	3	S	1. device	integer
			2. strategy	integer
			3. table	integer*2 array
BRKM	4	S	1. device	integer
			2. strategy	integer
			3. table	integer*2 array
			4. number of characters	integer
TIME	11	F	return value	integer*4
SETCM	12	S	1. command string	character
CIBUF	13	F	1. unit	integer
			return value	integer
COBUF	14	F	1. unit	integer
			return value	integer
MGTTY	16	F	1. unit	integer
			2. terminal type	integer
			return value	integer
MSTTY	17	F	1. unit	integer
			2. terminal type	integer
			return value	integer
LASTC	26	F	1. device	integer
			return value	integer
RTDSC	27	F	1. RT desc. address	integer
			1. RT desc. copy	integer array
			return value	integer

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Name	MON or oct	Fun	arguments/return	ERRCODE
	Sub number, purpose	data type	comments	set
GETRT	30	F	return value	integer
EXIOX	31	F	1. register content	integer
			2. dev.register address return value	integer
MSG	32	S	1. message	character
ALTON	33	S	1. page table number	integer
ALTOF	34	S	none
IOUT	35	S	1. radix	integer
			2. value	integer
NOWT	36	S	1. device	integer
			2. I/O flag 3. wait flag	integer
AIRDW	37	S	1. number of channels	integer
			2. channel numbers 3. read values 4. error flag	integer2 array integer2 array integer
SPCLO	40	F	1. unit	integer
			2. text string	character
			3. number of copies 4. print flag return value	integer integer integer
ROBJE	41	F	1. unit	integer
			2. buffer return value	integer*2 array integer
RUSER	44	F	1. user name	character
			2. buffer return value	integer*2 array integer
TERMO	52	S	1. device 2. mode	integer
MDLFI	54	F	1. file name return value	character integer
PASET	56	S	1-5 parameters	integer

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Name	MON oct	arguments/return	ERRCODE
		number, purpose	data type
PAGET	57 S	1-5 parameters	integer
RMAX	62 F	1. unit	integer
		2. number of bytes	integer*4
		return value	integer
ERMSG	64 F	1. error number	integer
QERMS	65 S	1. error number	integer
ISIZE	66 F	1. unit	integer
		return value	integer
OSIZE	67 F	1. unit	integer
		return value	integer
COMND	70 F	1. command string	character
DESCF	71 S	1. device	integer
EESCF	72 S	1. device	integer
SMAX	73 F	1. unit	integer
		2. byte count	integer*4
		return value	integer
SETBT	74 F	1. unit	integer
		2. byte pointer	integer*4
		return value	integer
REABT	75 F	1. unit	integer
		2. byte pointer	integer*4
		return value	integer
SETBS	76 F	1. unit	integer
		2. block size	integer
		return value	integer
SEIBL	77 F	1. unit	integer
		2. block number	integer
		return value	integer
RT	100 S	1. RT program	external or integer
SET	101 S	1. RT program	external or integer
		2. number of time units	integer
		3. basic unit	integer

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Name	MON or oct	Fun Sub	arguments/return	ERR/COND
		number, purpose	data type	comments
ABSET	102 S		1. RT program	external or integer
			2. seconds	integer
			3. minutes	integer
			4. hours	integer
INTV	103 S		1. RT program	external or integer
			2. number of time units	integer
			3. basic unit	integer
HOLD	104 S		1. number of time units	integer
			2. basic units	integer
ABORT	105 S		1. RT program	external or integer
CONCT	106 S		1. RT program	external or integer
			2. device	integer
DSCNT	107 S		1. RT program	external or integer
PRIOR	110 F		1. RT program	external or integer
			2. priority	integer
			return value	integer
UPDAT	111 S		1-5 time	integer
CLADJ	112 S		1. number of time units	integer
			2. basic units	integer
CLOCK	113 S		1. time	integer array
TUSED	114 F		return value	integer*4
FIX	115 S		1. segment number	integer
UNFIX	116 S		1. segment number	integer
RFILE	117 F		1. unit	integer
			2. return flag	integer
			3. memory address	array
			4. block number	integer
			5. length to be read	integer
			return value	integer

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Name	MON oct Sub	arguments/return	ERRCODE set
		number, purpose	data type
WFILE	120 F	1. unit	integer
		2. return flag	integer
		3. memory address	array
		4. block number	integer
		5. length to be written	integer
		return value	integer
WAITF	121 F	1. unit	integer
		2. return flag	integer
		return value	integer
RESRV	122 F	1. device	integer
		2. I/O flag	integer
		3. return flag	integer
		return value	integer
RELES	123 S	1. device	integer
		2. I/O flag	integer
PRSRV	124 F	1. device	integer
		2. I/O flag	integer
		3. RT program	external or integer
		return value	integer
PRLS	125 S	1. device	integer
		2. I/O flag	integer
DSET	126 S	1. RT program	external or integer
		2. delay	integer*4
DABST	127 S	1. RT program	external or integer
		2. time	integer*4
DINTV	130 S	1. RT program	external or integer
		2. time interval	integer*4
ABSTR	131 S	1. device	integer
		2. function	integer
		3. memory address	integer*4
		4. block address	integer
		5. number of blocks	integer

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Name	MON or Sub	arguments/return	ERRCODE
		number, purpose	data type
MEXIT	133 S	1. segment number	integer
RTEXT	134 S	none	-
RTWT	135 S	none	-
RTON	136 S	1. RT program	external or integer
RTOFF	137 S	1. RT program	external or integer
WHDEV	140 F	1. device	integer
		2. I/O flag	integer
		return value	integer
IOSET	141 F	1. device	integer
		2. I/O flag	integer
		3. RT desc. address	integer
		4. control flag	integer
		return value	integer
ERMON	142 S	1. error number	integer
		2. suberror number	integer
RSIO	143 S	1. execution mode	integer
		2. input device	integer
		3. output device	integer
		4. user number	integer
MAGTP	144 F	1. function	integer
		2. memory address	array
		3. unit	integer
		4. parameter 1	integer
		5. parameter 2	integer
		return value	integer
ACM	145 F	1. device	integer
		2. function	integer
		3. memory address	array
		4. destination	array
		5. word count	integer
		return value	integer
CAMAC	147 S	1. data	integer
		2. status	integer
		3. crate	integer
		4. station	integer
		5. subaddress	integer
		6. function	integer

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Name	MON	Fun or Sub	arguments/return	ERRORCODE
			number, purpose	data type
GL	150	S	1. value	integer
			2. crate	integer
GRTDA	151	F	1. name	hollerith
			return value	integer
IOXN	153	S	1. data	integer
			2. IOX code	integer
ASSIG	154	S	1. device	integer
			2. graded LAM	integer
			3. crate	integer
PLOTT	155	F	1.2 X,Y co-ordinates	integer
GRAPHIC			3. code	integer
			4. device	integer
			5. function	integer
			return value	integer
ENTSG	157	S	1. segment	integer
			2. page table	integer
			3. interrupt level	integer
			4. entry point	integer
FIXC	160	F	1. segment number	integer
			2. page number	integer
			return value	integer
INSTR	161	F	1. unit	integer
			2. text	character
			3. length	integer
			4. end character	integer
			return value	integer
OUTST	162	F	1. unit	integer
			2. text	character
			3. length	integer
			return value	integer
WSEG	164	S	1. segment number	integer
DIW	165	S	1. number of registers	integer
			2. input registers	integer*2 array
			3. input values	integer*2 array
			4. error value	integer

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Name	MON or Sub	arguments/return	ERRCODE set
		number, purpose	data type
DOLW	166 S	1. number of	integer
		registers
		2. registers	integer*2 array
		3. output values	integer*2 array
		4. masks	integer*2 array
		5. error value	integer
REENT	167 S	1. segment number	integer
HOLC	201 F	1. SDCB/RDCB	integer
		2. LDN	integer
		3. DCB address	integer
		4. DCB usize	integer
		5. DCB msize	integer
		return value	integer
EDTRM	206 S	1. EDFLA	integer
		2. RTUSF	integer
CPUST	262 F	1. ND number	integer
		2. buffer	integer*2 array
		return value	integer

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Notes:¶

If there was an error, the function returns the error code with the sign bit set.
The names of the Monitor Calls corresponding to these routines are:

Routine Monitor Call

INCH INBT

OUTCH OUTBT
Available on the ND-100 only.
Must start on a word boundary (ND-100 only) and end with an apostrophe.
The unit is defined by the FACTOR=fac specifier of the OPEN statement. The default is a 2-byte word on the ND-100, and a 4-byte word on the ND-500.
The radixes 2 and 16 are available on the ND-500 only.
The error number can be picked up from ERRCODE without change.

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Appendix D¶

LIBRARY UTILITY FUNCTIONS¶

D.1 TABLE OF LIBRARY UTILITY FUNCTIONS¶

Note: in the following table, "integer" in the column "data type" means default integer type; integer2 on the ND-100 and integer4 on the ND-500.

Name	Fun or Sub	arguments/return	data type	comments
EXCEPT	S	1. exception number	integer
		2. function	integer
		3. user routine	integer
		4. number of messages	integer
		5. number of traps	integer
		6. exception flags	logical array
		7. lower bound of 6.	integer
		8. upper bound of 6.	integer
EXCDEF	S	1. exception number	integer
		2. exception flags	logical array
		3. lower bound of 2.	integer
		4. upper bound of 2.	integer
EXCTERM	S	1. traceback print	integer
		2. statistics print	integer
		3. number of levels	integer
		4. file number	integer
GETMESS	F	1. exception number	integer
		return value	character*50
PRITRAC	S	1. trap	logical
PRIMESS	S	1. exception number	integer
RAN	F	1. seed value	integer*4
		return value	real*4	real*6, 48-bit f.p.H/W

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Name	Fun or Sub	arguments/return
		number, purpose
--------	------------	---------------------------------
RDEFVAL	S	1. exception number
		2. number of messages
		3. number of exceptions
		4. enable flag
--------	------------	---------------------------------
RCURVAL	S	1. exception number
		2. user routine
		3. number of messages
		4. number of exceptions
		5. exception count
		6. enable flag
--------	------------	---------------------------------
REXTERR	S	1. traceback print
		2. statistics print
		3. number of levels
		4. file number
		5. traceback print
		6. statistics print
		7. number of levels
		8. file number

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Appendix D¶

D.2 LIBRARY SUBPROGRAM DESCRIPTIONS¶

This section contains a full description of each subprogram provided in the FORTRAN library, for general utility purposes. Since the topic of handling errors and exceptions is of a rather special nature, it is described separately, see Section D.3. All services provided by the SINTRAN operating system are described in Appendix C.

D.2.1 THE RAN FUNCTION¶

The RAN function is for generating random numbers, which are uniformly distributed in the range between 0.0 inclusive and 1.0 exclusive.

The technique used for generating the random numbers is of the multiplicative congruential type.

The function returns a REAL4 value, REAL6 on a ND-100 with 48-bit floating point hardware.

The function may be invoked repeatedly, as follows:

RLVAR=RAN(INTVAR)

where

RLVAR	is assigned the next random number generated
INTVAR	is an INTEGER*4 variable

To get a series of random numbers, the first invocation of RAN must be made with the argument, here INTVAR, set to a large odd integer value prior to this invocation.

The RAN function stores a value in the argument on each invocation. This value will be used in the next invocation, to compute the next random number. This value is referred to as the seed.

There are no restrictions on the value which may be used for the seed. It should be initialized to a different value for successive runs if different series of random numbers are required.

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The RAN function uses the following algorithm to compute the value of the seed to be used for the next invocation:

SEED=69069*SEED+1(MOD 2**32)

SEED is a 32-bit number whose high order 24 bits are converted to a floating-point value to be returned as the function value.

D.3 ND-500 Traps and Exception Handling¶

ND-100 Exception Handling

The term "exception" covers, in addition to all defined hardware traps, special situations and errors detected by software. An exception handler is a routine to be activated when an exception occurs, and which takes appropriate recovery actions.

The exception number (16 bits) may be represented as shown below:

15	6	5
		0

where
bits 15-6 = System software identification (SSI)
bits 5-0 = Specific status code (SC)

and any number fed into the exception handling system will be in this form.

For FORTRAN, the SSI may contain three different ranges of numbers. For ND-500 hardware traps the range will be of the form 76xxB, where xx specifies the trap, see the table in Section D.3.1. The range 04xxB is reserved for FORTRAN runtime errors, and the range 51xxB is used by the exception handling system itself. Status codes are numbers allocated to a particular system. For example, the list of FORTRAN Exceptions given in Section D.3.11, gives an explanation of numbers in the range 401B: 457B, where 4 is the FORTRAN SSI. The range prefixed by 777B is not used by ND system software, and may be freely utilized in user systems.

A set of standard routines for exception handling for use with FORTRAN or PLANC has been developed. These are available in a standard library, and will be linked automatically if the user so wishes!

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For each error condition, the user may determine:

The number of times each error message is to be printed.
The number of times an error may occur before the program is abnormally terminated.
Whether a user-supplied exception handler is to be activated upon detection of an error.
Whether traceback of routine stack frames is to be printed when the error occurs or when the program terminates. (In case of traps, this includes a register dump.)
Printout of error statistics when the program terminates.

The library consists of the following routines:

Routine	Description
EXCEPT	disable/enable handling of specified exception
EXCDEF	reset handling of exception to default
EXCTERM	define action to be taken upon program termination
PRITRAC	print traceback of routine instances (subroutines)
PRIMESS	print error message
GETMESS	return error text (FORTRAN)
PGETMESS	return error text (PLANC)
RDEFVAL	read default exception handling parameters values
RCURVAL	read current exception handling parameters values
REXTERM	reat exception terminating condition

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In the following descriptions, the header of these routines is described, giving the number and types of the arguments. These routines are supplied with the standard ND FORTRAN library.

For the ND-500:

Traps and exceptions will be handled in the ND-500, providing they are locally enabled. There are default settings for all traps. If no local handling has been specified, or the trap has been disabled, then some traps may be handled as a system trap in the ND-100. The Monitor will then handle the trap in a standard manner, depending on the type of trap. System traps may also be disabled, but the user's right to modify trap handling may be restricted.

Handling of traps may be determined at load time or before execution through the commands LOCAL-TRAP-ENABLE, LOCAL-TRAP-DISABLE, SYSTEM-TRAP-ENABLE and SYSTEM-TRAP-DISABLE. These commands are available both in NLL and the Monitor, and set the default values to be used if no action is taken by the program. These commands are described in the ND-500 Loader/Monitor Manual, ND-60.136.

For the ND-100:

Exceptions will be handled provided they are locally enabled. There are default settings for all exceptions.

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Appendix D¶

D.3.1 ND-500 TRAPS TABLE¶

The following is a list of defined hardware traps, their corresponding bit number in the status, OTE, MTE and TEMM registers, and the name of the trap. For a more detailed explanation, see the ND-500 CPU Reference Manual (ND-05.009).

Bit no.	Exc. no.	Name	Mnemonic	D	msg	err
9	7611B	OVERFLOW	O		10	unl
11	7613B	INVALID OPERATION	IVO	*	10	unl
12	7614B	DIVISION BY ZERO	DZ	*	10	unl
13	7615B	FLOATING UNDERFLOW	FU		10	unl
14	7616B	FLOATING OVERFLOW	FO	*	10	unl
15	7617B	BCD OVERFLOW	BO		10	unl
16	7620B	ILLEGAL OPERAND VALUE	IVO	*	10	unl
17	7621B	SINGLE INSTRUCTION TRAP	SIT		0	unl
18	7622B	BRANCH TRAP	BT		0	unl
19	7623B	CALL TRAP	CT		0	unl
20	7624B	BREAKPOINT INSTRUCTION TRAP	BPT		0	unl
21	7625B	ADDRESS TRAP FETCH	ATF		0	unl
22	7626B	ADDRESS TRAP READ	ATR		0	unl
23	7627B	ADDRESS TRAP WRITE	ATW		0	unl
24	7630B	ADDRESS ZERO ACCESS	AZ		10	unl
25	7631B	DESCRIPTION RANGE	DR		10	unl
26	7632B	ILLEGAL INDEX	IX	*	1	0
27	7633B	STACK OVERFLOW	STO	*	1	0
28	7634B	STACK UNDERFLOW	STU		0	0
29	7635B	PROGRAMMED TRAP	PRT	*	10	unl
30	7636B	DISABLE PROCESS SWITCH TIMEOUT	DT	*	1	0
31	7637B	DISABLE PROCESS SWITCH ERROR	DE	*	1	0
32	7640B	INDEX SCALING ERROR	XSE	*	1	0
33	7641B	ILLEGAL INSTRUCTION CODE	IIC	*	1	0
34	7642B	ILLEGAL OPERAND SPECIFIER	IOS	*	1	0
35	7643B	INSTRUCTION SEQUENCE ERROR	ISE	*	1	0
36	7644B	PROTECT VIOLATION	PV	*	1	0

The D column refers to the default enabling of traps used by the standard exception handler library discussed in the next sections.
The * indicates that the trap is enabled if the default trap library settings are used.
msg = default maximum number of error messages.
err = default number of exceptions prior to abnormal termination.
unl = unlimited number

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Appendix D¶

D.3.1.1 ND-100 SIMULATED TRAPS¶

In the list of the simulated traps listed below, the D refers to the default enabling used by the standard exception handler library discussed in the next sections. * indicates that the exception is enabled if the default settings are used. For an explanation of msg and err see Section D.3.1.

Exc. no.	Name	D	msg	err
7614B	DIVISION BY ZERO	*	10	un1
7633B	STACK OVERFLOW	*	1	0

D.3.2 THE EXCEPT ROUTINE¶

The EXCEPT routine is used to modify the current exception handling conditions.

FORTRAN Specification:

SUBROUTINE EXCEPT (EXCINO, EXCFUN, EXCROUT, NOMSG, NOEXC,
                   EXCARR, EXCNOL, EXCNOH)
INTEGER EXCNO, EXCFUN, EXCROUT, NOMSG, NOEXC, EXCNOH, EXCNOL
LOGICAL EXCARR (EXCNOL:EXCNOH)

<standard library routine>
END

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Parameter values:¶

EXCNO Exception number or exception number group for the ND-500:

Value	Description
7600B	default group of traps to be set (see Section D.3.1)
5101B	LOGICAL array (EXCARR, EXCNOL and EXCNOH must be present, FORTRAN)
5102B	BITS (EXCARR must be present, PLANC)
7611B:7644B	specific trap number
400B	all FORTRAN errors (see Section D.3.11)
401B:457B	specific FORTRAN error
other	illegal

For the ND-100:

Value	Description
7600B	default group of simulated traps to be set (see Section D.3.1.1)
5101B	LOGICAL array (EXCARR, EXCNOL and EXCNOH must be present, FORTRAN)
5102B	BITS (EXCARR must be present, PLANC)
7614B:7633B	specific simulated traps
400B	all FORTRAN errors (see Section D.3.11)
401B:457B	specific FORTRAN error
other	illegal

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EXFUN Function¶


-1	disable exception(s) indicated by EXCNO and ignore all other exceptions. In addition, the parameters EXROUT, NOMSG and NOEXC will be ignored.
0	enable exception(s) indicated by EXCNO as TRUE, set new handler/values, and disable all other exceptions which are indicated as FALSE. For EXCNO values 7611B:7644B on the ND-500 (or 7614B:7633B on the ND-100) or 401B:457B, only the single exception thus specified, is enabled.
1	enable exception(s), indicated by EXCNO, do not modify handler/values, and ignore all other exceptions.
other	illegal

EXCROUT User defined exception handler routine¶

#0	routine address
0	no routine supplied

NOMSG Number of messages allowed before program is aborted¶


-1	any number of messages allowed
≥0	number of messages allowed (<2**31-1)
other	illegal

NOEXC Number of traps before program is aborted¶


-1	any number of exceptions allowed
≥0	number of exceptions allowed (<2**31-1)
other	illegal

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EXCARR LOGICAL array (FORTRAN) or BITS(PLANC) containing .TRUE. and .FALSE. for exceptions to be handled

EXCNOL (FORTRAN) Low limit of EXCARR

EXCNOH (FORTRAN) High limit of EXCARR

The handling of one or several exception conditions may be modified, selected through the EXCNO parameter. If this parameter is 5101B (FORTRAN) or 5102B (PLANC), the EXCARR parameter selects a set of exceptions to be handled. If the EXCFUN parameter is zero and EXCARR is present, the elements set to .TRUE. in this array will cause the corresponding exception to be enabled, while .FALSE. will cause it to be disabled. The array EXCARR must be declared as EXCARR (EXCARREXCNOH). For example, EXCARR(7611B:7644B) on the ND-500 or EXCARR (7614B:7633B) on the ND-100.

The EXCROUT parameter specifies the name of a user-supplied routine to be executed when the exception occurs. The routine should conform to the following formal specification:

In FORTRAN:

SUBROUTINE name (ierno)
INTEGER ierno

<user written exception handler>

END

The parameter ierno will transfer the error number to the exception handler. If the EXCROUT parameter is zero, the standard exception handler routine from the library is used.

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Examples - FORTRAN¶

Enable DIVISION BY ZERO detection using current exception values:

C DIVISION BY ZERO is trap number 12 on the ND-500
CALL EXCEPT (7641B,1,0,0,0)

For the ND-500 only: Enable OVERFLOW and allow a maximum of 2 error messages and 10 overflow errors before abnormal termination. Activate the user defined routine MYROUT each time the overflow trap occurs.

CALL EXCEPT (7611B,0,MYROUT,2,10)

Disable error handling for exponential functions, FORTRAN error numbers 431B, 432B, 433B, 437B.

LOGICAL ERRARRAY (431B:437B)
DATA ERRARRAY/.FALSE.,.FALSE.,.FALSE.,.TRUE.,
     .TRUE.,.TRUE.,.FALSE./
CALL EXCEPT (5101B,-1,0,0,0,ERRARRAY,431B,437B)

Manipulation of some exception settings. Assume the following are the current table settings for exceptions:

exc.no. (octal)	EXCROUT setting	msg	err	setting
431	A	10	un1	enabled
432	A	10	un1	enabled
433	A	10	un1	enabled
434	O	10	20	disabled
435	O	10	un1	enabled
436	O	10	un1	disabled
437	O	10	50	enabled

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Appendix D¶

EXCARR LOGICAL array (FORTRAN) or BITS(PLANC) containing .TRUE. and .FALSE. for exceptions to be handled

EXCNOL (FORTRAN) Low limit of EXCARR

EXCNOH (FORTRAN) High limit of EXCARR

The handling of one or several exception conditions may be modified, selected through the EXCNO parameter. If this parameter is 5101B (FORTRAN) or 5102B (PLANC), the EXCARR parameter selects a set of exceptions to be handled. If the EXCFUN parameter is zero and EXCARR is present, the elements set to .TRUE. in this array will cause the corresponding exception to be enabled, while .FALSE. will cause it to be disabled. The array EXCARR must be declared as EXCARR (EXCARREXCNOH). For example, EXCARR(7611B:7644B) on the ND-500 or EXCARR(7614B:7633B) on the ND-100.

The EXCROUT parameter specifies the name of a user supplied routine to be executed when the exception occurs. The routine should conform to the following formal specification:

In FORTRAN:

SUBROUTINE name (ierno)
INTEGER ierno

END

The parameter ierno will transfer the error number to the exception handler. If the EXCROUT parameter is zero, the standard exception handler routine from the library is used.

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After an error has occurred, the sequence of operations is as follows; the steps marked with an asterisk apply to traps on the ND-500 only:

Note: the details are slightly different in PLANC.

1) *If the exception is a trap, the trap routine is activated.

2) A system provided exception handler is called.

3) This handler updates the occurrence counter for this type of exception and activates the user exception handler if one has been specified.

4) If the traceback condition (see note 1) is true, the system outputs:

- register dump - traceback printout

5) If the message occurrence limit (NOMSG) has not been exceeded, or if the traceback condition (see note 1) is true, an error message is printed.

6) If the error count is less than or equal to the allowed number of occurrences for this exception type, control is returned to normal FORTRAN error handling.

Otherwise, the program is abnormally terminated with error statistics, if specified.

If the exception occurs during the execution of FORTRAN I/O statements (regardless of the type exception, SINTRAN, FORTRAN I/O, trigonometric error (430B:457B), or trap on the ND-500), the exception handler must not perform FORTRAN I/O. That is READ, WRITE, PRINT, OPEN, CLOSE, BACKSPACE, ENDFILE, or REWIND. Monitor Calls, however, may be called directly. Otherwise, FORTRAN I/O may be used, provided no new error situations are generated.

Note that, on the ND-500 only, in FORTRAN the STACK UNDERFLOW trap condition is handled by special software mechanisms and must, in order to ensure correct termination of the I/O activities, always be default enabled.

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Note 1: the traceback condition is evaluated by the following expression:

thiserror><'STACK UNDERFLOW' and  
( ( TRACEBACK<2 and  
( thiserror.NOMSG=unl or  
thiserror.numerrors in 0 : thiserror.NOMSG ) )  
or  
( TRACEBACK≥1 and  
(thiserror.NOEXC><UNL and  
NOT thiserror.numerrors in 0 : thiserror.NOEXC ) ) )

where

thiserror.numerrors is the current value of the number of exceptions of this type which have occurred.

EXAMPLES - FORTRAN¶

Enable DIVISION BY ZERO detection using current exception values:

C DIVISION BY ZERO is trap number 12 on the ND-500  
CALL EXCEPT (7614B,1,0,0,0)

For the ND-500 only:
Enable OVERFLOW and allow a maximum of 2 error messages and 10 overflow errors before abnormal termination. Activate the user-defined routine MYROUT each time the overflow trap occurs.

CALL EXCEPT (7611B,0,MYROUT,2,10)

Disable error handling for exponential functions, FORTRAN error numbers 431B, 432B, 433B, 437B.

LOGICAL ERRARRAY (431B:437B)  
DATA ERRARRAY/.FALSE..FALSE..FALSE..TRUE.,  
               .TRUE...TRUE...FALSE./  
CALL EXCEPT (5101B,-1,0,0,0,ERRARRAY,431B,437B)

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Manipulation of Exception Settings¶

Assume the following are the current table settings for exceptions:

exc.no. (octal)	EXCROUT setting	msg	err	setting
...
431	A	10	unl	enabled
432	A	10	unl	enabled
433	A	10	unl	enabled
434	O	10	20	disabled
435	O	10	unl	enabled
436	O	10	unl	disabled
437	O	10	50	enabled
...

If the following call were executed,

CALL EXCEPT (51018,0,MYROUT,5,-1,ERRARRAY,431B,437B)

C ERRARRAY as declared in the previous example

then the table settings would be changed as follows:

exc.no. (octal)	EXCROUT setting	msg	err	setting
...
431	A	10	unl	disabled
432	A	10	unl	disabled
433	A	10	unl	disabled
434	MYROUT	5	unl	enabled
435	MYROUT	5	unl	enabled
436	MYROUT	5	unl	enabled
437	O	10	50	disabled

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Appendix D¶

D.3.3 The EXCDEF Routine¶

EXCDEF is used to set the default exception handling values for a given set of exceptions. This is functionally equivalent to calling EXCEPT with the default parameter values for each of the exceptions specified, but is more convenient and relieves the programmer from knowing the defaults.

FORTRAN Specification:¶

SUBROUTINE EXCDEF (EXCNO, EXCARR, EXCNOL, EXCNOH)
INTEGER EXCNO, EXCNOL, EXCNOH
LOGICAL EXCARR (EXCNOL:EXCNOH)
(standard library routine)
END

Parameter values:¶

EXCNO¶

Exception number or exception number group for the ND-500:

7600B	default setting (see Section D.3.1)
5101B	LOGICAL array (EXCARR, EXCNOL and EXCNOH present, FORTRAN)
5102B	BITS (EXCARR present PLAN C)
7611B:7644B	default setting for specific trap number (see Section D.3.1)
400B	all FORTRAN errors
401B:457B	specific FORTRAN error
other	illegal

For the ND-100:

7600B	default setting (see Section D.3.1)
5101B	LOGICAL array (EXCARR, EXCNOL and EXCNOH present, FORTRAN)
5102B	BITS (EXCARR present, PLAN C)
7614B:7633B	default setting for specific simulated traps (see Section D.3.1)
400B	all FORTRAN errors
401B:457B	specific FORTRAN error
other	illegal

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EXCARR LOGICAL array (FORTRAN) or BITS (PLANC)
containing .TRUE. for exceptions to be handled,
.FALSE. for those that should remain as they are

EXCNOL (FORTRAN) Low limit of EXCARR

EXCNOH (FORTRAN) High limit of EXCARR

The EXCARR parameter selects a set of exception conditions, like in the EXCEPT routine. Alternatively, one specific exception may be selected through the EXCNO parameter.

EXAMPLES - FORTRAN¶

Reset handling of all traps and FORTRAN errors to default:

C ALL TRAPS (ON ND-500), ALL SIMULATED TRAPS (ND-100)  
C  
CALL EXCDEF (7600B)

C  
C ALL FORTRAN ERRORS  
C  
CALL EXCDEF (400B)

C  
C SET DEFAULT PROGRAM TERMINATION CONDITIONS  
CALL EXCTERM (0, 1, 20, 0); % on the ND-500  
CALL EXCTERM (0, 0, 20, 0); % on the ND-100

This setting is identical to the setting at the beginning of execution of a FORTRAN program.

Reset special error handling for exponential functions, error numbers 431B, 432B, 433B and 437B, but keep possible handling of other exceptions:

LOGICAL ERRARRAY (431B:437B)  
DATA ERRARRAY/.TRUE.,.TRUE.,.TRUE.,.FALSE.,  
+ .FALSE.,.FALSE.,.TRUE./  
CALL EXCDEF (5101B,ERRARRAY,431B,437B)

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D.3.4 THE EXCTERM ROUTINE¶

EXCTERM may be called to determine how the printing of traceback and error statistics information is done. If it has been called more than once, the last call applies at program termination.

FORTRAN Specification:

SUBROUTINE EXCTERM (TRACEBACK, PRSTAT, NOLEV, FNUMB)
INTEGER TRACEBACK, PRSTAT, NOLEV, FNUMB
<standard library routine>
END

Parameter value:¶

TRACEBACK traceback print, for all errors:


0	: no traceback (default)
1	: traceback upon abnormal termination
2	: traceback upon error
other	: illegal

PRSTAT error statistics print upon end of program, for all errors:


0	: no statistics output (default, ND-100)
1	: print statistics (default, ND-500)
other	: illegal

NOLEV maximum number of levels to process when a traceback is provided:


>	: maximum number of stack levels to print, default 20
other	: illegal

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FNUMB
1-127
0
other

Note the difference between a file with number 1 and terminal 1.

D.3.5 THE PRITRAC ROUTINE¶

PRITRAC is a utility routine to print a traceback of routine instances (stack frames) after an exception. The routine is called from a user handler, or automatically upon abnormal termination of the job if traceback has been selected (in the EXCEPT call referring to the exception condition raised).

FORTRAN Specification:¶

SUBROUTINE PRITRAC (TRAP)
LOGICAL TRAP

END

Parameter value (which is ignored in the ND-100 version):

TRAP
.TRUE. if called while a trap is being handled.
.FALSE. should be set for any other condition.

Note that the default maximum number of stack levels to be printed is 20.

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D.3.6 THE PRIMESS ROUTINE¶

The PRIMESS routine will print the error message, corresponding to the parameter value, on the standard output device (unit 1).

FORTRAN Specification:

SUBROUTINE PRIMESS (EXCNO)  
INTEGER EXCNO  
<standard library routine>  
END

Parameter values:


EXCNO	Exception number (for the ND-500)

The parameter (EXCNO) must be in the range 7611B:7644B (traps) or 4018:457B (FORTRAN errors).


	Exception number (for the ND-100)

The parameter (EXCNO) must be in the range 7614B:7633B (simulated traps) or 4018:457B (FORTRAN errors).

D.3.7 THE GETMESS/PGETMESS ROUTINE¶

GETMESS/PGETMESS will return the error text corresponding to the specified exception number.

FORTRAN Specification:

FUNCTION GETMESS (EXCNO)  
C this function must be declared to be of type character in the  
C calling program  
INTEGER EXCNO  
CHARACTER*50 GETMESS  
<standard library routine>  
END

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Parameter values:¶

EXCNO The number of an exception condition (for the ND-500)

EXCNO must (for the ND-500) be the number of a defined exception condition, in the range 7611B:7644B (traps) or 401B:457B (FORTRAN error).

EXCNO must (for the ND-100) be the number of a defined exception condition, in the range 7614B:7633B (simulated trap) or 401B:457B (FORTRAN error).

D.3.8 THE RDEFVAL ROUTINE¶

RDEFVAL may be called to read the default values of the exception parameters corresponding to a given exception number (EXCNO).

FORTRAN Specification:¶

SUBROUTINE RDEFVAL (EXCNO, NOMSG, NOEXC, ENABL)
INTEGER EXCNO, NOMSG, NOEXC,
LOGICAL ENABL
<standard library routine>
END

Parameter values:¶

Parameter	Description
EXCNO	Exception number
NOMSG	Default number of messages allowed
NOEXC	Default number of exceptions allowed
ENABL	Logical parameter .TRUE. if exception is enabled as default.

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D.3.9 THE RCURVAL ROUTINE¶

RCURVAL may be called to read the current values of the exception parameters corresponding to a given exception number (EXCNO).

FORTRAN Specification:¶

SUBROUTINE RCURVAL (EXCNO, EXCROUT, NOMSG, NOEXC, EXCCOUNT, ENABL)
INTEGER EXCNO, EXCROUT, NOMSG, NCEXC, EXCCOUT
LOGICAL ENABL
(standard library routine)
END

Parameter values:¶

Parameter	Description
EXCNO	Exception number
EXCROUT	Address of current user exception handler or zero
NOMSG	Current number of messages allowed before termination
NOEXC	Current number of exceptions allowed before termination
EXCCOUNT	Current exception count
ENABL	Logical parameter .TRUE. if exception is enabled at the moment

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D.3.10 THE REXTERM ROUTINE¶

REXTERM is used to read the exception terminating condition.

FORTRAN Specification:¶

SUBROUTINE EXCTERM (TRACEBACK, PRSTAT, NOLEV, FNUMB,
                    DTRACEBACK, OPRSTAT, DNOLEV, DFNUMB)
INTEGER TRACEBACK, TRSTAT, NOLEV, FNUMB, DTRACEBACK, DPRSTAT,
        DNOLEV, DFNUMB
<standard library routine>
END

The first parameters will read the current value of the variables represented by the parameters in the EXCTERM routine. The last four read the default values of the corresponding variables.

See the EXCTERM routine for the parameter descriptions.

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Appendix D¶

D.3.11 FORTRAN EXCEPTIONS¶

dec	oct	name	msg	err
257	401	FATAL FORMATTING SYSTEM ERROR	1	0
258	402	TOO LOW PARENTHESES LEVEL IN FORMAT	1	0
259	403	ILLEGAL CHARACTER IN FORMAT	1	0
260	404	ILLEGAL TERMINATION OF FORMAT	1	0
261	405	OUTPUT RECORD SIZE EXCEEDED	10	unl
262	406	FORMAT REQUIRES GREATER INPUT RECORD	10	unl
263	407	INTEGER OVERFLOW ON INPUT	10	unl
264	410	INPUT RECORD SIZE EXCEEDED	10	unl
265	411	BACKSPACE ILLEGAL	10	unl
266	412	BAD CHARACTER ON INPUT	10	unl
267	413	REAL OVERFLOW ON INPUT	10	unl
268	414	REAL UNDERFLOW ON INPUT	10	unl
269	415	STRING DOES NOT START ON A WORD BOUNDARY	10	unl
270	416	REAL OVERFLOW ON OUTPUT	10	unl
271	417	FORMAT SPECIFICATION DOES NOT APPLY	1	0
272	420	OVERFLOW IN EXPONENT ON INPUT	10	unl
273	421	WRONG NUMBER OF PARAMETERS IN CALL	1	0
274	422	TOO MANY FILES OPENED	1	0 ND-100 only
276	424	MIXING OF BINARY/ASCII ILLEGAL	1	0
277	425	NO MORE BUFFERS AVAILABLE	1	0
278	426	NON-FATAL ERROR (CHARACTER)	10	unl ND-500 only
279	427	FATAL ERROR (I/O)	1	0
280*	430	I/O ERROR WITHOUT SPECIAL HANDLING	0	0
281	431	ZERO BASE AND NEGATIVE EXPONENT	10	unl
282	432	BASE LESS THAN ZERO IN EXPONENTIATION	10	unl
283	433	OVERFLOW IN EXPONENTIATION	10	unl
284	434	NEG. ARG. IN SQUARE ROOT	10	unl
285	435	TOO LARGE ARG. IN SINE	10	unl
286	436	TOO LARGE ARG. IN COSINE	10	unl
287	437	TOO LARGE ARG. IN EXP-FUNCTION	10	unl
288	440	ZERO OR NEG. ARG. IN LOGARITHM	10	unl
289	441	BOTH ARGS. ZERO IN ARC-TAN	10	unl
294	446	TOO LARGE ARG. IN HYPERB. SINE	10	unl
295	447	TOO LARGE ARG. IN HYPERB.COSINE	10	unl
296	450	TOO LARGE ARG. COMPLEX ABS OR SQUARE ROOT	10	unl
302	456	ILLEGAL ARG. IN ARC-SINE/COSINE	10	unl
303	457	ILLEGAL ARG. IN TAN	10	unl

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* = must be enabled
msg = default maximum number of error messages
err = default number of exceptions prior to abnormal termination
unl = unlimited number

Numbers not listed are currently not used. All FORTRAN errors except 430B are default enabled.

All languages:¶

The hardware traps are listed in Section D.3.1.

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Appendix E

STORAGE MAPPING¶

ND FORTRAN data types are stored in the following way:

LOGICAL*1¶


0	0	V

7 1 0

Bits 7-1 : set to 0
Bit 0(V) : 0 = .FALSE.
1 = .TRUE.

LOGICAL*2¶


0	0	V

15 1 0

Bits 15-1 : set to 0
Bit 0(V) : 0 = .FALSE.
1 = .TRUE.

LOGICAL*4¶


0	0	V

31 1 0

Bits 31-1 : set to 0
Bit 0(V) : 0 = .FALSE.
1 = .TRUE.

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INTEGER*1¶

S	value
7	6

Bit 7 : 0 = greater than or equal to zero
1 = negative
Bits 6-0 : value held in twos-complement form.

INTEGER*2¶

S	value
15	14

Bit 15 : 0 = greater than or equal to zero
1 = negative
Bits 14-0 : value held in twos-complement form.

INTEGER*4¶

S	value
31	30

Bit 31 : 0 = greater than or equal to zero
1 = negative
Bits 30-0 : value held in twos-complement form.

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Appendix E¶

REAL*4 (ND-500 or NORD-10/ND-100) with 32-bit floating-point hardware option¶

S	Exponent	mantissa
31	30	22 21

Bit 31:
- 0 = greater than or equal to zero
- 1 = negative

Bits 30-22: Binary exponent
- Stored with a bias of 256 (400 octal). This is the power of 2 that the mantissa must be multiplied by. A value of 256 means that the mantissa is the value.
- If the exponent is 0, the whole value is zero.

Bits 21-0: Mantissa
- Stored without the 0.5 (0.1 binary) excess, unless the value is zero. The binary point is one place to the left of the mantissa. The mantissa is normalised so that 0.5 ≤ mantissa < 1.0

REAL*6 (NORD-10/ND-100 with 48-bit floating-point hardware option)¶

S	Exponent	mantissa
47	46	32 31

Bit 47:
- 0 = greater than or equal to zero
- 1 = negative

Bits 46-32: Binary exponent
- Stored with a bias of 40000 octal. Zero exponent means that the whole value is zero.

Bits 31-0: Mantissa
- Stored with all bits included. Binary point is immediately to the left of Bit 31.

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REAL*8 (all machines)¶

S	Exponent	mantissa
63	62	54 53 0

Bit 63:
0 = greater than or equal to zero
1 = negative

Bits 62-54: Binary exponent
Stored with a bias of 256 (= 400 octal). A zero exponent means the whole value is zero.

Bits 53-0: Mantissa
Stored without the 0.5 (= 0.1 binary) excess unless the value is zero. The mantissa is normalized so the 0.5 ≤ mantissa < 1.0. The binary point is one place to the left of Bit 53.

COMPLEX*8¶

2 consecutive REAL*4 values.

COMPLEX*12¶

2 consecutive REAL*6 values.

COMPLEX*16¶

2 consecutive REAL*8 values.

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Appendix E

CHARACTER*N¶

N consecutive bytes.
A character is addressed via a descriptor.

On the ND-500, the descriptor is 2 words:

length
address of the first character in string

31

ON NORD-10/ND-100, the descriptor is 2 words:

address of the first word
C

15 14 11 10

If C (bit 15 of 2nd. word) = 0, the string starts in the high-order byte of the first word; if 1, then it is in the low-order byte.

The following tables give the size in BYTES of each data type for the various machines.

NUMERIC (fw,sc)¶

Only ND-500:¶

(fw / 2) +1 consecutive bytes

A packed decimal operand is addressed via a descriptor.
The descriptor takes two words:

31 16 15 0

sc	fw
address of first byte

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Table 1¶

NORD-10 OR ND-100 WITH 48-BIT FLOATING-POINT HARDWARE¶

Data Type	Length in Bytes	Alignment (Note 1)
CHARACTER*1 (Note 2)	1	Byte

LOGICAL (Note 3)	2	Word
LOGICAL*2	2	Word
LOGICAL*4	4	Word

INTEGER (Note 3)	2	Word
INTEGER*2	2	Word
INTEGER*4	4	Word
DOUBLE INTEGER	4	Word

REAL (Note 3)	6	Word
REAL*4 (Note 4)	6	Word
REAL*6 (Note 4)	6	Word
REAL*8	8	Word
DOUBLE PRECISION (Note 5)	8	Word

COMPLEX	12	Word
COMPLEX*8 (Note 4)	12	Word
COMPLEX*12 (Note 4)	12	Word
COMPLEX*16 (Note 5)	16	Word
DOUBLE COMPLEX (Note 5)	16	Word

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TABLE 2¶

NORD-10 OR ND-100 WITH 32-BIT FLOATING-POINT HARDWARE¶

The CHARACTER, LOGICAL, and INTEGER types are as for the 48-bit table above. The other data types are listed below.

Data Type	Length in Bytes	Alignment (Note 1)
REAL (Note 3)	4	Word
REAL*4 (Note 4)	4	Word
REAL*6 (Note 4)	4	Word
REAL*8 (Note 5)	8	Word
DOUBLE PRECISION (Note 5)	8	Word

TABLE 3¶

ND-500¶

Data Type	Length in Bytes	Alignment (Note 1)
CHARACTER*1 (Note 2)	1	Byte
LOGICAL (Note 3)	4	Word
LOGICAL*1	1	Byte
LOGICAL*2	2	Half-Word
LOGICAL*4	4	Word
INTEGER (Note 3)	4	Word
INTEGER*1	1	Byte
INTEGER*2	2	Half-Word
INTEGER*4	4	Word
DOUBLE INTEGER	4	Word
REAL (Note 3)	4	Word
REAL*4 (Note 4)	4	Word
REAL*6 (Note 4)	4	Word
REAL*8 (Note 5)	8	Word
DOUBLE PRECISION (Note 5)	8	Word
COMPLEX	8	Word
COMPLEX*8 (Note 4)	8	Word
COMPLEX*12 (Note 4)	8	Word
COMPLEX*16 (Note 5)	16	Word
DOUBLE COMPLEX (Note 5)	16	Word
NUMERIC (fw, sc)	(fw / 2) +1	Byte

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Notes¶

For the NORD-10 and ND-100, a word is 16 bits = 2 bytes. For the ND-500, a word is 32 bits = 4 bytes.
For CHARACTER strings of length N, the length is N bytes.
These are default values. The meaning of these attributes can be modified by the DEFAULT command.
REAL6 and REAL4 both mean single precision irrespective of the machine the program is executed on. The alternatives are provided for completeness and comments since the 48-bit format uses 6 bytes for a REAL value. Similar remarks apply to COMPLEX8 and COMPLEX12.
The DOUBLE PRECISION forms are identical on all machines. For the NORD-10 and ND-100, the implementation uses softwareroutines and is relatively slow.

Common Mapping¶

To allocate addresses within a common block, the following algorithm is used:

Place the first variable on a word boundary.
Place each subsequent variable on the first available alignment boundary at, or following the end of the previous variable.

It is the user's responsibility to ensure that the COMMON blocks are correctly defined. Particular care should be taken over the COMMON blocks shared between unlike processors (i.e., ND-100 and ND-500).

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RESTRICTION¶

ANSI FORTRAN 77 implies that an INTEGER and a REAL data item occupy the same amount of storage. For the ND-500 and the ND-100 with 32-bit floating-point hardware with DEFAULT INTEGER*4 specified, this condition is met.

However, for the ND-100 with 48-bit floating-point, hardware programs cannot be accepted as ANSI FORTRAN 77 standard, if equivalent storage occupation for INTEGER and REAL is required by either different COMMON definitions or by EQUIVALENCE statements.

CODE AND DATA SIZES¶

At the end of a compilation, the compiler indicates the total storage requirements of all the program units compiled by the last COMPILE command.

All the numbers given are in decimal, representing for the ND-100 the number of words, and for the ND-500, the number of bytes.

The values given are:

PROG SIZE is the size of the program code. On the ND-100 in single-bank operation (i.e., SEPARATE-DATA OFF), this figure also includes the data areas of the program, since they are not separated.
DATA SIZE is the size of the data areas used by the program, but excluding any COMMON blocks. This size is placed in the data bank in ND-500 programs and if SEPARATE-DATA ON is used in ND-100 programs. (The figure is omitted when using SEPARATE-DATA OFF in ND-100 programs.)
COMMON SIZE is the total of all the maximum sizes of the COMMON blocks found in the last compilation. It is placed in the data bank where applicable, or at the high address if SEPARATE-DATA OFF is used. (See the NRL and RT-Loader manuals for alternative methods of placing COMMON.)

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4) STACK SIZE is the sum of all the local storage requirements of all the units compiled in the last COMPILE command. These areas are obtained dynamically on entry to each program unit, and released on exit. If only one unit was compiled, it accurately reflects that unit's stack requirement (but not the routines it calls). The actual stack size should include enough for the longest nest of CALL's or function references, including library calls. The figure is omitted on the ND-100 with REENTRANT OFF, since there is no stack in this case.

Note that if LIBRARY-MODE is ON, these figures represent the total if all units are incorporated in a program. If only a selection is used, the figures are accordingly reduced.

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INTERFACES TO OTHER LANGUAGE PROGRAMS¶

ND FORTRAN has a standard calling sequence for its subroutine and function invocations. This will make it easier to interface programs and subprograms written in other languages with those written in FORTRAN. This interface is described in detail first, followed by examples showing how to use it to interface to other languages on both the ND-100 and ND-500.

F.1 FORTRAN INTERFACES ON THE ND-100¶

Each FORTRAN subprogram holds its local variables in a local data area. If a program, comprising a number of subprograms, is compiled as non-reentrant, then each local data area will be in a separate stack for each subprogram. If such a program is compiled as reentrant, then the local data area for each subprogram will be dynamically allocated from a single stack. The B-register must always address the appropriate stack element during execution of a FORTRAN subprogram.

OFFSET FROM THE B-REG (OCTAL) IN BYTES	CONTENT
-200	LINK - link register, address for normal return
-177	PREVB - previous B-register, reloaded on exit
-176	FREES - points to the free area of stack which immediately follows this stack element
-175	EOS - points to the word immediately following the whole stack
-174	SYS - run time system use
-173	ERRCODE - ERRCODE (value)
-172	stack element - first parameter address if any
	free area - free area of the stack
	FIO use - one word, FORTRAN I/O use
	buffers - one word, number of buffers
	exc ptr - one word, exception handler pointer

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In FORTRAN, there are always three words following the stack. If the FORTRAN I/O system is to be used, and the program is non-reentrant, these should be initialized. The first word points to a special FORTRAN I/O area whose name is 5FIO-BL, and the second word should be zero. The third word, which is used by the EXCEPTION HANDLER, is called 5EXCINF. If the program is reentrant, these 3 words are initialized at run time, to zero, on entry to the FORTRAN main program.

The free area following the current stack element should always be large enough to contain the work areas for the FORTRAN run time routines (except the I/O routines in non-reentrant execution).

When FORTRAN calls an EXTERNAL entry point, the registers are used as follows:

L = return address
B = current stack element; must be restored on return
T = number of parameters
A = parameter list address
D = address of descriptor for the return value if the call is to a function which returns a character string
X = unused
P = entry point of called routine

On return from a function, the value of the function is returned as follows:

Type	Register
LOGICAL2, INTEGER2	A-register
LOGICAL4, INTEGER4	AD-register
REAL*4 (32-bit floating-point hardware)	AD-register
REAL*6 (48-bit floating-point hardware)	TAD-register
REAL8, COMPLEX, COMPLEX16	A-register points to the result
CHARACTER	result resides in storage described by descriptor which D-reg pointed at on entry

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For character functions, a memory area of the required size has been allocated by the calling routine before invoking of the function, and the 0-register points to a descriptor upon entry to the function.

Reentrant FORTRAN routines assume that the parameter addresses are already in position (-172B from the B-register and onwards) at entry to the routine. It is the responsibility of the calling routine to place them there. From the calling viewpoint, they lie at +6 from the free area and onwards. Thus the addresses are not copied.

If a subroutine has alternate returns specified in its dummy argument list, these are not included in the parameter list. Instead, the alternate return value (0 for normal return) is set in the ERRCODE position in the caller's stack element. This value may then be used in a COMPUTED GO TO after return has been made to the caller.

The parameter list consists of a sequence of words, one for each dummy argument. For arithmetic variables or expressions and logical variables or expressions, the corresponding word contains the address of the variable. For arrays of arithmetic or logical types, the word contains the address of the first element of the array.

For character variables or expressions, the word contains the address of a descriptor consisting of two words.

Word 1	Address of word containing first character
Word 2	15

Bit 15 of word two is 0 if the string starts in the left-hand (high-order) byte of the word, and is 1 if it starts in the right-hand byte.

Bits 14 - 11 are used by the commercial instruction set and should normally be zero.

For character arrays, the parameter word contains the address of a descriptor for the first element of the array (i.e., one whose address part is for the start of the array, and whose length is that of a single element of the array).

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For two-bank programs, all parameter values and their descriptors, if character, must be in the data bank.

The ASSEMBLY statement modifies the calling sequence to EXTERNAL program units. It can be used where the external routine is written in MAC, NPL, or PLANC with the SPECIAL option.

The calling sequence is modified as follows:

Only integer parameters or array names may occur in direct calls.

The arguments are passed in registers. Integer values are contained in the register; array names are passed as the address of their first word. The arguments 1 to 4 are in T, A, D, and X-registers respectively. It is not possible to modify the FORTRAN arguments in the called routine, unless they are arrays.

The return address is one word beyond the contents of the L-register at entry to the routine.

Note that functions returning DOUBLE PRECISION and COMPLEX values do so in a manner incompatible with the 2090 series of FORTRAN compilers.

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F.2 FORTRAN INTERFACES ON THE ND-500¶

Each FORTRAN subprogram holds its local variables in a local data area. A program, comprising a number of subprograms, will result in each local data area being in a separate stack for each subprogram. The B-register must always address the appropriate stack element during execution of a FORTRAN subprogram.

OFFSET FROM THE B-REG (OCTAL) IN BYTES	CONTENT
0 PREVB	previous B-register, reloaded on exit
4 RETA	link register, address for normal return
10 FREES	points to the free area of stack which immediately follows this stack element
14 ERRCODE	ERRCODE value
20 stack element	first parameter address if any
free area	free area of the stack

On return from a function, the value of the function is as follows:

LOGICAL1, LOGICAL2, INTEGER1, INTEGER2, LOGICAL4, INTEGER4: I1-register
REAL*4, (32-bit floating-point): A1-register
REAL*8, (48-bit floating-point): D1-register
COMPLEX*8: A1-register, A2-register
COMPLEX*16: D1-register, D2-register
CHARACTER, NUMERIC (fw,sc): result resides in storage described by descriptor which R-reg pointed at on entry.

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For character functions, a memory area of the required size has been allocated by the calling routine before invocation of the function, and the R-register points to a descriptor upon entry to the function.

If a subroutine has alternate returns specified in its dummy argument list, these are not included in the parameter list. Instead, the alternate return value (0 for normal return) is set in the ERRCODE position in the caller's stack element. This value may then be used in a COMPUTED GO TO after return has been made to the caller.

The parameter list consists of a sequence of words, one for each dummy argument. For arithmetic variables or expressions and logical variables or expressions, the corresponding word contains the address of the variable. For arrays of arithmetic or logical types, the word contains the address of the first element of the array.

For character variables or expressions, the word contains the address of a descriptor consisting of two words:


word 1	15 length in bytes 0
word 2	address of word containing first character

For character arrays, the parameter word contains the address of a descriptor for the first element of the array (i.e., one whose address part is for the start of the array, and whose length is that of a single element of the array).

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F.3 Invoking PLANC from FORTRAN¶

All PLANC routines called from FORTRAN should be 'STANDARD'. Any PLANC routine called from FORTRAN must contain an INISTACK invocation unless the FORTRAN program is compiled using the REENTRANT-MODE command on ND-100 or FIXED-MODE OFF on ND-500.

Example 1 - simple subroutine call¶

To call a subroutine with no complex arithmetic actual arguments, the following can be written in FORTRAN:

EXTERNAL PLSUBR
INTEGER I
REAL R
C CALL A SUBROUTINE WRITTEN IN PLANC
CALL PLSUBR (I,R)

and the corresponding PLANC code is:

MODULE msubr
EXPORT plsubr
INTEGER ARRAY : stack (1:1000)
ROUTINE STANDARD VOID,VOID (INTEGER,REAL) : plsubr (int,rl)
INISTACK stack
% body of routine
ENDROUTINE
ENDMODULE

Example 2 - simple function call¶

To invoke a function which returns a non-complex arithmetic result.

In FORTRAN:

EXTERNAL PLFUNC
REAL X,Y,PLFUNC
DOUBLE PRECISION D
C INVOKE A FUNCTION WRITTEN IN PLANC
Y=PLFUNC (X,D)

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In PLANC:

ROUTINE STANDARD VOID, REAL (REAL, REAL8) : plfunc (r1, db)
INISTACK stack
% PLANC REAL8 is the same as FORTRAN DOUBLE PRECISION
... RETURN
ENDROUTINE

Example 3 - use of logical arguments¶

On the ND-100:¶

FORTRAN LOGICAL2 corresponds to PLANC BOOLEAN. FORTRAN LOGICAL4 is the following PLANC data type:

TYPE boolean4 = RECORD
  BOOLEAN : unused % first word always zero
  BOOLEAN : value % contains actual value
ENDRECORD

LOGICAL*4 cannot be returned from a PLANC STANDARD function.

In FORTRAN:

EXTERNAL PLBOOL
LOGICAL PLBOOL, V
LOGICAL*4 M4
V = PLBOOL (V, M4)

In PLANC:

ROUTINE STANDARD VOID, BOOLEAN (BOOLEAN, boolean4) : plbool(m, m4)
INISTACK stack
IF m4.value THEN
  m RETURN
ENDIF
NOT m RETURN
ENDROUTINE

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On the ND-500:¶

FORTRAN LOGICAL*4 corresponds to PLANC BOOLEAN. The FORTRAN LOGICAL*2 data type has no direct equivalent in PLANC. FORTRAN LOGICAL*2 can be handled in PLANC in the following way:

In FORTRAN:

EXTERNAL PLBOOL
LOGICAL PLBOOL,V
LOGICAL*2 M2
V=PLBOOL (V,M2)

In PLANC:

ROUTINE STANDARD VOID,BOOLEAN (BOOLEAN,INTEGER2) :plbool(m,m2)
INISTACK stack
% the 2 integers must be contiguous in memory
    INTEGER2 : int1,int2
    BOOLEAN : bool1=int1
    m2:=int2
    0:=int1
    IF bool1 THEN
        m RETURN
    ENDIF
    NOT m RETURN
ENDROUTINE

Example 4 - Complex Arguments and Functions¶

FORTRAN COMPLEX has no direct corresponding data type in PLANC. It may be defined as follows:

TYPE complex = RECORD
    REAL : re  % real part
    REAL : im  % imaginary part
ENDRECORD

Similarly the equivalent of FORTRAN DOUBLE COMPLEX is:

TYPE complex = RECORD
    REAL8 : dre
    REAL8 : dim
ENDRECORD

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These types, once defined, may be used just like other record data types.

On the ND-100:¶

In FORTRAN:

COMPLEX C, CFUNC
EXTERNAL CFUNC
REAL R
C INVOKE A PLANC FUNCTION WHICH RETURNS A COMPLEX RESULT
C = CFUNC (R)

In PLANC:

ROUTINE STANDARD VOID, complex (REAL) : cfunc (r)
INISTACK stack
complex : c
r=:c.im:=c.re   % store value in two identifiers
c RETURN
ENDROUTINE

On the ND-500:¶

In FORTRAN:

COMPLEX C, CFUNC
EXTERNAL CFUNC
REAL R
C INVOKE A PLANC FUNCTION WHICH RETURNS A COMPLEX RESULT
C = CFUNC (R)

In PLANC:

ROUTINE STANDARD VOID, VOID (REAL) : cfunc (r)
INISTACK stack
complex : c
r=:c.im:=c.re   % store value in two identifiers
% set up values to be returned
$* A1:=c.re; A2:=c.im
RETURN
ENDROUTINE

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Example 5 - Character String Arguments¶

Since FORTRAN passes character strings through a descriptor, PLANC routines must accept these as records. It is often most convenient to recast the FORTRAN string descriptor as a PLANC bytes pointer. Thus:

On the ND-100:¶

TYPE ftnstring = RECORD % a blank must precede the -1
  BYTES : ftnchars (0: -1) % character data
ENDRECORD

TYPE ftndesc = RECORD PACKED
  ftnstring POINTER : cstring % address of string
  INTEGER RANGE (0:1B) : coddbyte % left/right byte start
  INTEGER RANGE (0:17B) : cunused % unused
  INTEGER RANGE (0:3777B) : clength % length of string
ENDRECORD

Then in FORTRAN:¶

CHARACTER H*20
INTEGER I, J
EXTERNAL HSUB
CALL HSUB ( H(I:J) )

which can be picked up in PLANC by:

ROUTINE STANDARD VOID, VOID (ftndesc) : hsub (hij)
  INISTACK stack
  BYTES POINTER : bp
  ADDR (hij.cstring.ftnchars &
    (hij.coddbyte: hij.clength-1+hij.coddbyte) )=:bp
% bp now contains the address of the FORTRAN character string
ENDROUTINE

On the ND-500:¶

TYPE ftnstring = RECORD
  BYTES : ftnchars (0: -1) % character data
ENDRECORD % a blank must precede the -1

TYPE ftndesc = RECORD
  INTEGER RANGE (0:777777777B) : clength
  ftnstring POINTER : cstring
ENDRECORD

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Then in FORTRAN:

CHARACTER H*20  
INTEGER I, J  
EXTERNAL HSUB  
CALL HSUB ( H(I:J) )

which can be picked up in PLANC by:

ROUTINE STANDARD VOID, VOID (ftndesc) : hsub (hij)  
INITSTACK stack  
BYTES POINTER : bp  
ADDR (hij.cstring.ftnchars (0 : hij.clength-1) ):=bp  
% bp now contains the address of the FORTRAN character string  
ENDROUTINE

Example 6 - functions returning a character value¶

The definition of character data types must be made as in example 5. But in this case there can be no true return value for the function, so the PLANC code must simulate the return.

On the ND-100:¶

In FORTRAN:

CHARACTER H*20, HFUNC*10  
EXTERNAL HFUNC  
H(1:10) = HFUNC (...)

In PLANC:

ROUTINE STANDARD VOID, VOID : hfunc  
INITSTACK stack  
BYTES POINTER : bp  
ftndesc POINTER : dreg  
$* COPY SD DA; STA dreg % return value descriptor  
ADDR (dreg.cstring.ftnchars &  
(dreg.coddbtye : dreg.clength-1+dreg.coddbtye) )=:bp  
'0123456789'=:IND (bp) % set 'return value'  
ENDROUTINE

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On the ND-500:¶

In FORTRAN:¶

CHARACTER H*20,HFUNC*10
EXTERNAL HFUNC
H(1:10) = HFUNC (...)

In PLANC:¶

ROUTINE STANDARD VOID,VOID : hfunc
INISTACK stack
BYTES POINTER : bp
ftndesc POINTER : rreg
$* R=:B.rreg  % return value descriptor
ADDR [rreg.cstring.[t]fuchars (0 : rreg.clength-1) ]=:bp
'0123456789':=IND (bp)  % set 'return value'
ENDROUTINE

F.4 INVOKING FORTRAN FROM PLANC¶

All FORTRAN subprograms invoked from PLANC must be IMPORT'ed as STANDARD routines. FORTRAN functions have out-values, but no FORTRAN routines have in-values.

Example 1 - a simple subroutine call

Call a FORTRAN subroutine with non-complex arithmetic dummy arguments.

In PLANC:¶

IMPORT ( ROUTINE STANDARD VOID,VOID (REAL,REAL8) : fsubr )
REAL : r
REAL8 : d
... fsubr (r,d) % call the FORTRAN subroutine

In FORTRAN:¶

SUBROUTINE FSUBR (R,D)
REAL R
DOUBLE PRECISION D C
END

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Example 2 - a simple function¶

To invoke a function, returning a non-complex arithmetic result.

In PLANC:

IMPORT (ROUTINE STANDARD VOID,VOID,INTEGER (INTEGER4) : ifunc)

% 
INTEGER : k
INTEGER4 : kd
ifunc (kd)=:k % invoke the FORTRAN function

In FORTRAN:

INTEGER FUNCTION IFUNC (KD)
INTEGER*4 KD
IFUNC=...
RETURN
END

Example 3 - use of logical arguments¶

PLANC BOOLEAN is the same as LOGICAL in FORTRAN, LOGICAL2 on the ND-100 and LOGICAL4 on the ND-500. LOGICAL4 on the ND-100 or LOGICAL2 on the ND-500 may be simulated as in example 3 in the previous section.

On the ND-100:¶

In PLANC:

IMPORT (ROUTINE STANDARD VOID,BOOLEAN (boolean4) : lfunc)

% 
boolean4 : m4
IF lfunc (m4) THEN...

In FORTRAN:

LOGICAL FUNCTION LFUNC (M4)
LOGICAL*4 M4
LFUNC=...
RETURN
END

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On the ND-500¶

In PLANC:

IMPORT ( ROUTINE STANDARD VOID, BOOLEAN (INTEGER2) : lfunc )
% the 2 integers must be contiguous in memory
INTEGER2 : int1, int2
BOOLEAN : bool1=int1
% put a value in the boolean data-element
...:=bool1
IF lfunc (int2) THEN ...

In FORTRAN:

LOGICAL FUNCTION LFUNC (M2)
LOGICAL*2 M2
LFUNC=...
RETURN
END

Example 4 - complex arguments and out-values¶

FORTRAN COMPLEX can be simulated in PLANC by the type declarations of example 4 in the previous section.

In PLANC:

IMPORT ( ROUTINE VOID, complex (REAL) : cfunc )
%
complex : c
REAL : r
% on the ND-100 invoke the FORTRAN function normally
cfunc(r):=c
% on the ND-500 invoke the FORTRAN function normally, but assembler
% is required to get the returned function value
cfunc (r)
$* A1:=c.re; A2:=c.im

In FORTRAN:

COMPLEX FUNCTION CFUNC (R)
REAL R
CFUNC=CMPLX (R,R)
RETURN
END

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Example 5 - Character String Arguments¶

FORTRAN handles character strings by means of descriptors, which can be declared in PLANC as in example 5 in the previous section. These descriptors must be created in PLANC before invocation of the FORTRAN subprogram takes place.

In PLANC:

IMPORT ( ROUTINE STANDARD VOID, VOID (ftndesc) : hsub)
ftndesc : ed  
BYTES : arg (1:100)   % begins in left byte of word
INTEGER : i, j
% now transfer arg (i:j) to FORTRAN
ADDR(arg (i) ) FORCE ftnstring POINTER := fd.cstring
% first byte - the following 2 lines are for the ND-100 only
1-(iMOD 2) := fd.coddbyte % left/right byte
0 := fd.cunused
%

j-i+1 := fd.clength    % length of string
hsub (fd)              % invoke FORTRAN subprogram

In FORTRAN:

SUBROUTINE HSUB (FD)
CHARACTER FD* (*)
C
END

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Example 6 - Character Functions¶

Characters cannot be returned by FORTRAN to PLANC as out-values. The memory area for the returned string must be allocated before invoking the function and a special calling sequence is required.

In PLANC:¶

IMPORT { ROUTINE STANDARD VOID, VOID : hfunc }
ftndesc : fd
BYTES : val (0:19)      % value returned here
ftndesc POINTER : fdp

% ADDR(val [0] ) FORCE ftstring POINTER=:fd.cstring
% first byte - the following 2 lines are required for the ND-100 only
O =:fd.coddbyte
O =:fd.cunused

% MAXINDEX (val,1)-MININDEX (val,1)+1=:td.clength
ADDR (fd) =:fdp
% on the ND-100 use:
$* LDA fdp; COPY SA DD % return descriptor address

% on the ND-500 use:
$* R:=fdp          % return descriptor address

% hfunc            % put result in 'val'

In FORTRAN:¶

CHARACTER * (*) FUNCTION HFUNC
HFUNC
RETURN
END

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F.5 CALLING COBOL FROM FORTRAN¶

On both the ND-100 and the ND-500, a FORTRAN program may call a subprogram written in COBOL. Parameters are transferred by reference between FORTRAN and COBOL. The data types which correspond in FORTRAN and COBOL are as follows:

FORTRAN	COBOL
INTEGER*2, 16-bits	PIC S9(n) COMPUTATIONAL where 1≤n≤4
INTEGER*4, 32-bits	PIC S9(n) COMPUTATIONAL where 5≤n≤10
REAL	COMPUTATIONAL-2
HOLLERITH strings	PIC X(n) where n is the number of bytes

COMPUTATIONAL-2 variables may only be used as a parameter in a subroutine call to or from COBOL, or to convert to/from COMPUTATIONAL-3 variables.

For example:

In FORTRAN:

INTEGER*2 INT2
REAL RL
INTEGER*4 INT4
INT2=56
RL=54.12345
INT4=123456
C CALL A COBOL SUBROUTINE
CALL CBSUB (INT2,RL,INT4,'HOLL')

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In COBOL:¶

PROGRAM-ID. CBSUB.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 CB-REAL        PIC S9(3)V9(6) COMP-3.
LINKAGE SECTION.
01 FTN-INT2       PIC S9(4) COMP.
01 FTN-INT4       PIC S9(6) COMP.
01 FTN-REAL       COMP-2.
01 FTN-HOLLERITH  PIC X(4).
PROCEDURE DIVISION USING FTN-INT2
                           FTN-REAL
                           FTN-INT4
                           FTN-HOLLERITH.

PARA-1.
* CONVERT THE FORTRAN REAL VALUE TO THE INTERNAL COBOL FORM
  MOVE FTN-REAL         TO CB-REAL.

On ND-500 it is possible to transfer parameters of type CHARACTER and NUMERIC between FORTRAN and COBOL routines. The routine that calls the COBOL routine must be compiled with the command:

COBOL-INTERFACE <routine-name>

In FORTRAN:¶

NUMERIC (5,3) N
CHARACTER*4 CH
CALL CBROU (CH,N)

In COBOL:¶

PROGRAM-ID. CBROU.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 FTN-STRING     PIC X(4).
01 FTN-NUMERIC    PIC S9(3)V9(2) PACKED DECIMAL.
PROCEDURE DIVISION USING FTN-STRING, FTN-NUMERIC.

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F.6 Calling FORTRAN From COBOL¶

On both the ND-100 and the ND-500, a COBOL program may call a subprogram written in FORTRAN. Parameters are transferred by reference between FORTRAN and COBOL. The data types which correspond in FORTRAN and COBOL are as follows:

FORTRAN	COBOL
INTEGER*2, 16-bits	PIC S9(n) COMPUTATIONAL where 1 ≤ n ≤ 4
INTEGER*4, 32-bits	PIC S9(n) COMPUTATIONAL where 5 ≤ n ≤ 10
REAL	COMPUTATIONAL-2
HOLLERITH strings	PIC X(n) where n is the number of bytes

COMPUTATIONAL-2 variables may only be used as a parameter in a subroutine call to or from COBOL, or to convert to/from COMPUTATIONAL-3 variables.

Parameters from COBOL must start on a word boundary, ND-100 only.

For example:

In COBOL:

DATA DIVISION  
WORKING-STORAGE SECTION.  
01 FTN-INT2        PIC S9(4) COMP  VALUE 123.  
01 FTN-INT4        PIC S9(6) COMP  VALUE 123456.  
01 CB-REAL         PIC S9(3)V9(6) CP-3 VALUE -2.71.  
01 FTN-REAL        COMP-2.  
01 FTN-HOLLERITH   PIC X(10)  VALUE 'A123456789'.  
01 FTN-HLENGTH-WDS PIC S9(4) COMP  VALUE 5.

* NUMBER OF CHARACTERS PER WORD IS DIFFERENT ON THE ND-500

PROCEDURE DIVISION.  
    PARA-1.  
    * CONVERT THE INTERNAL COBOL FROM THE FORTRAN REAL FORM  
        MOVE CB-REAL          TO FTN-REAL.  
    * CALL A FORTRAN SUBROUTINE  
        CALL 'FTNSUB' USING  
            FTN-INT2  
            FTN-REAL  
            FTN-INT4  
            FTN-HOLLERITH  
            FTN-HLENGTH-WDS.

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Appendix F

In FORTRAN:¶

SUBROUTINE FTNSUB (INT2, RL, INT4, HSTRING, HLENGTH)  
INTEGER*2 INT2, HLENGTH, HSTRING (HLENGTH)  
INTEGER*4 INT4  
C MAY NOW ACCESS VALUES PASSED FROM COBOL AND RETURN VALUES  
C TO COBOL IN THE NORMAL MANNER  
RETURN  
END

On ND-500 it is also possible to transfer parameters of type CHARACTER and NUMERIC between FORTRAN and COBOL routines. The FORTRAN routine that is called from COBOL must be compiled with the command:

COBOL-INTERFACE <routine-name>

In COBOL:¶

DATA DIVISION.  
WORKING-STORAGE SECTION.  
01 FTN-STRING    PIC X(4) VALUE 'TEST'.  
01 FTN-NUMERIC   PIC S9(3)V9(2) PACKED-DECIMAL VALUE 345.67.  
PROCEDURE DIVISION.  
P.1.  
CALL "FTNSUB" USING FTN-STRING, FTN-NUMERIC.

In FORTRAN:¶

SUBROUTINE FTNSUB (CH, N)  
CHARACTER*4 CH  
NUMERIC (5,2) N  
END

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F.7 MAC SUBROUTINES (ND-100 ONLY)¶

When writing subroutines or functions to be called from FORTRAN, the user should clearly understand the format of the run-time stack, and the use of registers in the calling sequence, see Section F.1.

There is a marked difference between reentrant and non-reentrant routines with regard to the available methods for acquiring local workspace.

F.7.1 NON-REENTRANT ROUTINES¶

In this case, there is no space available in the FORTRAN routine's local area (addressed by the B-register) which can be used by a called subroutine. It is the called subroutine's responsibility to acquire the local areas it needs on its own behalf.

An example of how to address parameters from a MAC routine is as follows:

)9BEG
)9ENT SUBR
SUBR,
    SWAP   SA DB   % if called as CALL SUBR (I,R)
    STA    SAVB    % save FORTRAN's B-reg.
    LDA    I 0,B   % first parameter (I)
    ......
    LDF    I 1,B   % second parameter (R) 1
    ......
    LDA    SAVB
    COPY   SA DB   % restore FORTRAN's B-reg.
    EXIT
SAVB,0
)9END

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Appendix F¶

In order to mix MAC routines with FORTRAN, it is recommended that the following calling sequence be used (see Sections F.7.4 and F.7.5.):

)9BEG
)9ENT SUBR
SUBR, COPY SL DX % return address
JPL I (5IN17 % create a stack unit
FRAME % size (in words) of the local frame
STACK % address of stack space
STS2 % total size of stack
0 % or 1 if two-bank operation
0 % for debug use

% routine starts here
..............
)9END JPL I (5LEAV % return to caller

This will also aid the Symbolic Debugger to identify the FORTRAN routines and trace the stack frames correctly.

F.7.2 REENTRANT ROUTINES¶

Routines which can be shared among several programs can be called only from reentrant FORTRAN routines (see REENTRANT command, Section 12.8). They can use the standard FORTRAN stack, which has been initialised by a FORTRAN program. The MAC subroutines must not alter the length of the stack, nor interfere with the two words which follow it. The acquisition of the local stack area and return, can be done as follows:

)9BEG
)9ENT SUBR
SUBR, COPY SL DX % save routine return
JPL I (5ENTR % acquire next frame
SIZE % size of frame (in words)
COPY SA DX % B-reg addresses stack
......

% frame
JPL I (5LEAV % return up stack
)FILL
)9END

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F.7.3 ALTERNATE RETURNS¶

An alternate return is handled by setting the appropriate value (from 1 upwards) corresponding to the number of the asterisks in the parameter list of the CALL statement, into the return code slot of the calling routine. Zero must be set if there is no alternate return taken, but one was expected by the CALL.

The address of the caller's stack frame can be obtained by:

LDX  SAVB      % non-reentrant case
or
LDX  -177,B    % reentrant case

and then the return value is set by:

LDA  RETNV     % value for return
STA  -173,X    % store in caller's error code

F.7.4 CALLING FORTRAN SUBROUTINES¶

For non-reentrant FORTRAN routines, the parameter list must be built at its correct place in the called routine's stack frame. For example:

LDA  (PADR     % parameter list address
JPL  I (FSUB   % call FORTRAN subroutine

PADR,       % first parameter address
I           % second parameter address

I,54        % first parameter value
R, -3.141593 % second parameter value

LDX  -176,B   % free stack space
LDA  (I       % first parameter address
STA  6,X     % first parameter position
LDA  (R
STA  7,X     % second parameter position

JPL  I(FSUB

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Appendix F¶

F.7.5 INVOKING FORTRAN INTRINSIC FUNCTIONS¶

All FORTRAN library routines must be treated like reentrant FORTRAN subroutines, and space provided on the local stack for the library workspace. To set up a local stack (and/or stack frame) see Sections F.7.1 and F.7.2. The amount of space required by the library for its stack frame can generally be determined by the data type of the returned value. These values are subject to small changes without notice, therefore a certain margin should be allowed.

DATA TYPE	STACK SIZE
INTEGER*2	10
INTEGER*4	40
REAL	65
DOUBLE PRECISION	160

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ND FORTRAN Reference Manual¶

Appendix G¶

HOLLERITH¶

G.1 HOLLERITH CONSTANTS¶

The ANSI FORTRAN 77 Standard does not accept Hollerith constants. It merely gives recommendations as to their use in an appendix to retain some compatibility with previously existing programs.

ND FORTRAN implements these recommendations, with a few minor additions and changes, to retain compatibility with programs which run on the NORD-10 FORTRAN compiler. Details are as follows:

CONSTANTS

Hollerith constants may have one of two forms. The first is:

nHh h h...hn
1 2 3

where

n is a non-negative number.
h...hn are the n characters in the source program which immediately follow the H.

Blanks are significant among the h, but the h cannot contain a carriage return, line feed, or tab characters. The internal representation of a Hollerith constant is the sequence of h, as ASCII characters with the parity bit set to zero.

The second form is:

"h......h"

The double-quote characters ", octal 42, is the delimiter for the Hollerith string. The h characters inside the double-quotes may be replaced by any character except carriage return, line feed or tab characters. If the string is to contain a double-quote character, two of these should be written.

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Appendix G¶

They can be used as constants only in DATA statements, as actual arguments in subroutine or function invocations, as the right-hand side of an arithmetic assignment statement, or as the value given to a symbolic constant.

They may not appear in any other context; in particular, as values for output, or in expressions.

IN ASSIGNMENT STATEMENTS

A Hollerith constant as the right-hand side of an assignment statement may be moved to an arithmetic or logical variable or array element name without any form of conversion. The ASCII characters are assigned byte-by-byte to the storage of the left-hand side, starting at the leftmost byte. Padding with blanks or truncation occurs on the right to the length of the storage for the target. See Appendix E for the sizes of the variables. Character variables cannot receive Hollerith constants.

IN DATA STATEMENTS

An arithmetic or logical variable may take a Hollerith constant from the constant list as its initial value in a DATA statement. The assignment is as for the assignment statement. The correspondence of data list and constant list is preserved. Character variables cannot receive Hollerith values.

AS ACTUAL ARGUMENTS

Hollerith constants used as actual arguments must match their corresponding dummy arguments for storage length. No padding will occur; but if the actual argument is longer, only the first characters are used in the dummy argument. The dummy argument cannot be of type CHARACTER.

AS A SYMBOLIC CONSTANT VALUE

The Hollerith constant is assigned to the symbolic constant as if it were being assigned to a variable of the type of the symbolic constant on the target machine of the compilation. The resulting arithmetic value is then the value of the symbolic constant. The allowable data types are only INTEGER2 and INTEGER4.

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ND FORTRAN Reference Manual¶

Appendix G¶

IN A RELATIONAL COMPARISON

Variables can be compared with Hollerith data in an IF statement, or general logical expression. The Hollerith data is treated as though it were assigned to a variable of the same data type as the other operand of the comparison, and the comparison is performed as for that other data type. Character strings cannot be compared with Hollerith data.

A-FORMAT FOR HOLLERITH DATA

If the format Aw is used when the corresponding I/O list item is arithmetic or logical, then the data transfer is done without conversion, except for parity bits being cleared on input (unless the parity option has been coded on the OPEN statement for the file, see Section 8.3.1).

On input, the w input characters are treated like a Hollerith constant and assigned as in the assignment statement. On output, w output characters are written from the storage of the arithmetic or logical item.

RESTRICTIONS

If a logical variable has been assigned a Hollerith value, then its use as a logical value will be unpredictable.

Real, double precision and complex variables containing Hollerith values may be moved, but any form of arithmetic operation may give unpredictable results due to hidden optimisations or conversions.

It is recommended that Hollerith constants be avoided wherever possible. Character variables may be equivalenced as an alternative. If Hollerith constants must be used, it is recommended that the exact length be specified to prevent the implied padding and truncation. This should ease the transport and maintenance of these non-standard features.

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ND FORTRAN Reference Manual¶

INDEX¶

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ND FORTRAN Reference Manual¶

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INDEX LIST¶

Index term	Reference
A format descriptor	207
actual
arguments	239
declarator	37
adjustable
arrays	36
dimensions	44
ALIGNMENT-ND500 command	297
arithmetic
array expression	103
constant	27
expression	79
operand	79
operator	79
Arithmetic IF statement	129
array
adjustable	36
assumed-size	36
declarator	37
definition	34
element name	35
expressions	103
size of	34
storage, order of elements in	35
subscript	35
Array Processing Function Library	299
ARRAY-INDEX-CHECK command	278
ASSEMBLY statement	69
Assigned GO TO statement	127
assignment statements
arithmetic	115
character	119
conversion in	116
logical	117
statement label	118
asterisk
as a dummy argument	221
BACKSPACE statement	178
BCD-ROUNDING command	284
Blank COMMON
difference between named COMMON and	50
storage sequence of	50

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Index¶

Index term	Reference
Block COMMON
definition	49
storage sequence of	50
BLOCK DATA statement	257
BLOCK DATA subprogram restrictions	257
Block IF statement	131
BN and BZ format descriptors	204
character
alphanumeric	4
constant	31
data type	25
expression	86
operands	86
operator	86
special	4
substrings	38
Type statement	56
CHARACTER Alignment	316
CHARACTER and Hollerith	316
character set, FORTRAN	4
CHECK-NUMBER-OF-PARAMETERS command	279
CLOSE statement	177
COBOL-INTERFACE command	283
collating sequence	5
columns	7
combined compile and execution	270
comment line	7
COMMON-BLOCK-CHECK command	309
COMMON block storage sequence	50
COMMON statement	49
compilation of source programs	264
COMPILE command	264
compiler
command syntax	262
defaults	293
invocation command	261
sample program	13
COMPLEX
constant	30
data type	25
expression	79
Type statement	54
Computed GO TO statement	125
conditional compilation	285
CONDITIONAL-COMPILING command	286
CONSTANT command	288

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Index¶

Index Term	Reference
constant expression
arithmetic	82
character	88
logical	95
constants
arithmetic	27
character	31
complex	30
double precision	29
integer	27
logical	31
real	28
CONTINUE statement	141
control statements	123
creating FORTRAN libraries	284
CROSS-REFERENCE command	272
DATA statement	73
data types	25
debugging	285
DEBUG-MODE command	285
DEFAULT command	293
DEFINE command	269
DELETE-INTRINSIC command	298
digit, definition	4
dimension
bounds	43
declarator	34
DIMENSION statement	43
DO
FOR-ENDDO statements	139
loop	135
loop, range of	135
statement	135
statement, execution	137
WHILE-ENDDO statements	139
documentation commands	307
DOCUMENT-SYSTEM command	307
DOUBLE PRECISION
constant	29
data type	25
expression	79
Type statement	54
dummy
argument	214
array declarator	37
procedure	219

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Index¶

Index Term	Reference
E and D format descriptors	201
editing, use of format descriptors for	196
EJECT command	275
ELSE statement	132
ELSEIF statement	131
END statement	144
ENDFILE statement	179
ENDIF statement	132
END-OF-FILE command	267
End-of-File Specifier	153
ENTRY statement	244
EQUIVALENCE statement	46
Error specifier	154
executable statement	9
EXIT command	305
exponent
double precision	29
real	29
expression
arithmetic	79
arithmetic array	103
array	103
character	86
constant	95
definition of	79
evaluation	96
logical	92
relational	89
subscript	35
substring	38
external
functions	239
procedure	10
statement	65

| F format descriptor | 198 | | file | | | definition | 148 | | File Accessing | 317 | | FIXED-DATA-AREA command | 300 | | FLOATING command | 296 | | Format | | | descriptors | 192 | | specifications | 191 | | specifier and identifier | 152 |

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Index¶

Term	Reference
formatted
data transfer	158
records, printing of	165
FORTRAN
character set	4
statement	9
FORTRAN and COBOL routines	283
FORTRAN-100 command	271
FORTRAN-500 command	271
functions
definition	213
G format descriptor	232
global item	6
GLOBAL-CHECK-ALL command	309
GLOBAL-MODE command	304
GO TO statement
Assigned	127
Computed	125
Unconditional	124
H format descriptor	205
HEADING-TEXT command	276
HELP command	263, 305
I and J format descriptors	197
IF statement
Arithmetic	129
Logical	130
IMPLICIT
statement	61
IMPLICIT command	295
implied
DO lists	157
type rules for identifiers	25
INCLUDE command	266
INPUT statement	167
input, list-directed	159
Input-Output
Buffer Allocation	317
file access	150
file format	149
list-directed	158
lists	156
statements	147

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Index Term¶

Index Term	Reference
Input-Output
status specifier	154
terms and concepts	147
INQUIRE statement	181
INSTRUCTION command	290
INTEGER
constant	27
data type	25
expression	79
Type statement	54
Interprocedural Error Diagnostic	309
INTRINSIC
statement	66
INTRINSIC functions	222
INTRINSIC functions, removing of	298

| keyword | 6 |

| L format descriptor | 206 | | letter definition | 4 | | LIBRARY-MODE command | 284 | | line | | | comment | 7 | | continuation | 7 | | initial | 7 | | LINK-SEGMENT command | 269 | | LIST command | 275 | | listing information | 272 | | LOAD command | 268 | | local item | 6 | | LOCAL-STACK-SIZE command | 302 | | LOGICAL | | | array expressions | 108 | | constant | 31 | | data type | 25 | | expression | 92 | | operand | 92 | | operator | 92 | | Type statement | 54 | | Logical IF statement | 130 | | loop | | | control variable | 314 | | definition | 313 |

| main program | 253 |

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Index¶

Index term	Reference
MAIN-STACK-SIZE command	301
MOVE-INSTRUCTIONS command	296
ND100-EXTENDED command	297
nonexecutable statement	9
numeric editing	196
O format descriptor	208
octal values	27
OPEN statement	168
operands
arithmetic	80
character	86
logical	92
operators
arithmetic	80
character	86
logical	92
precedence order of	92
relational	89
optimization of program execution-time	288
OPTIMIZE command	288
OUTPUT statement	167
output, list-directed	160
OUTPUT-FILE command	306
P format descriptor	199
packed decimal	284
PAGE-SIZE command	274, 306
PARAMETER
statement	63
PARAMETER-CHECK command	309
parentheses	96
PAUSE statement	143
precedence of arithmetic operators	80
PRINT statement	166
PRINT-CALL-HIERARCHY command	308
PRINT-COMMON-BLOCK-INFORMATION command	308
PRINT-INVERSE-HIERARCHY command	308
procedure
definition	10
external	10
main	10
PROG-FILE command	267

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Index¶

Index term	Reference
program
addresses	274
stack	300
unit	10
PROGRAM statement	253
PROGRAM-MAP command	274
Programming Techniques	313

READ statement	161
REAL
constant	28
data type	25
expression	79
Type statement	54
REAL-TIME-MODE command	283
record
definition	147
record specifier	155
REENTRANT-MODE command	282
relational
array expressions	106
expression	89
operand	89
operator	89
RESERVE-WORK-SPACE command	298
results for arithmetic array expressions	105
RETURN statement	248
REWIND statement	179
RUN command	269
RUN TIME MODES	281

S, SP and SS format descriptors	203
SAVE statement	67
SEGMENT-FILE command	268
SEPARATE-DATA command	281
slash format descriptor	206
special characters	4
special names in INTRINSIC functions	222
STANDARD-CHECK command	277
statement
executable	9
FORTRAN	9
functions	236
label	9
nonexecutable	9
STOP statement	142

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Index¶

Index term	Reference
subroutine
definition	242
in-line	289
referencing to a	242
subprogram restrictions	243
subscript
array	35
expression	35
substring
character	38
expression	38
SUBSTRING-EXPRESSION-CHECK command	280
symbolic name	6
SYMBOLIC-NAME-LENGTH command	278
syntactic item	6
SYSTEM-NAME command	307
T, TL, TR and rX format descriptors	205
tab positions	8
TEST-MODE command	280
text format descriptor	204
Type statements	54
UNASSIGNED-VARIABLE-CHECK command	279
Unconditional GO TO statement	124
unformatted
data transfer	158
UNIT command	295
Units	151
USE-APF-LIBRARY command	299
variable
as dummy argument	217
variables
definition	33
WRITE statement	163
Z format descriptor	209

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Function	Definition
sin (z)	sin (x) cosh (y) + i cos (x) sinh (y)
cos (z)	cos (x) cosh (y) - i sin (x) sinh (y)

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ND FORTRAN¶

Reference Manual¶

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ND FORTRAN Reference Manual¶

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NOTICE¶

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PRINTING RECORD¶

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Manuals Update¶

Documentation Department¶

Graphic Center¶

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PREFACE¶

THE PRODUCT¶

THE READER¶

PREREQUISITE KNOWLEDGE¶

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RELATED MANUALS¶

HOW TO USE THE MANUAL¶

RESTRICTIONS, DEVIATIONS, AND INCOMPATIBILITIES¶

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ND FORTRAN Reference Manual¶

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ND FORTRAN Reference Manual¶

Page 10¶

TABLE OF CONTENTS¶

Page 11¶

Table of Contents¶

4 THE DATA STATEMENT¶

5 EXPRESSIONS¶

6 ARRAY EXPRESSIONS¶

7 ASSIGNMENT STATEMENTS¶

Page 12¶

Section¶

8 CONTROL STATEMENTS¶

9 INPUT/OUTPUT STATEMENTS¶

Page 13¶

Section¶

10 FORMAT SPECIFICATIONS¶

11 FUNCTIONS AND SUBROUTINES¶

Page 14¶

Section¶

12 MAIN PROGRAM¶

13 BLOCK DATA SUBPROGRAM¶

14 COMPILER COMMANDS¶

Page 15¶

Section¶

15 ADVANCED FORTRAN PROGRAMMING¶

Page 16¶

Section¶

Page 17¶

Page 18¶

Chapter 1¶

Introduction¶

Page 19¶

ND FORTRAN Reference Manual¶

Page 20¶

ND FORTRAN Reference Manual¶

INTRODUCTION¶

1.1 THE NOTATION¶

Page 21¶

1.2 FORTRAN CHARACTER SET¶

Page 22¶

ND FORTRAN Reference Manual¶

INTRODUCTION¶

Page 23¶

1.3 FORTRAN TERMS AND CONCEPTS¶

Page 24¶

ND FORTRAN Reference Manual¶

INTRODUCTION¶

1.3.1 Lines¶

Page 25¶

ND FORTRAN Reference Manual¶

INTRODUCTION¶

For example:¶

Page 26¶

1.3.2 Statements¶

Page 27¶