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:PROG File Format Reference

Full path: PROG-FILE-FORMAT.md

A comprehensive description of the SINTRAN III :PROG (program) file format used by the Nord Relocating Loader (NRL), the SINTRAN @DUMP / @RECOVER commands, and (in extended form) by the ND-500 Loader Monitor (NLL) when running in COMPUTER-MODE 100.

Authoritative sources used to compile this document - Reference-Manuals/ND-60.066.04 ND Relocating Loader.md - sections 1.1.4, 1.1.6, 1.1.7, 1.4.2 and Appendix A - Reference-Manuals/ND-60.136.04A ND-500 Loader Monitor.md - section on COMPUTER-MODE 100 (:PROG produced by NLL) - Reference-Manuals/ND-60.096.01 MAC ... User's Guide.md - section 5.5 (the related :BPUN absolute-binary format that :PROG is contrasted with) - Reference-Manuals/SINTRAN-COMMANDS-REFERENCE.md - @DUMP, @RECOVER, @PLACE-BINARY, @DUMP-PROGRAM-REENTRANT - SINTRAN/OS/SEGMENTS-INTRO-AND-DEEP-DIVE.md - how @RECOVER maps a PROG file into a background segment

Anything not directly attested in those sources is marked UNVERIFIED or ASSUMPTION.

1. What a :PROG File Is

A :PROG file is a memory image of a loaded and linked program, stored on a SINTRAN III mass-storage file with default file type :PROG. Unlike :BRF (Binary Relocatable Format) it is not relocatable - all symbols have already been resolved by the NRL and the program occupies fixed virtual addresses inside a 64KW (one bank) or 2x64KW (two bank) ND-100/NORD-10 address space.

A :PROG file is "ready for execution": SINTRAN can bring it back into the caller's address space with a single @RECOVER command, set the program counter to the recorded start address, and the program runs.

Aspect :BRF :BPUN :PROG
Relocatable? Yes No No
Contains symbol info? Yes No No
How produced Compiler / assembler NRL *BPUN or MAC )BPUN NRL *DUMP / *PROG-FILE, or SINTRAN @DUMP
How loaded NRL *LOAD @PLACE-BINARY, hardware loader, MAC )9READ @RECOVER (or NLL $RECOVER for NLL-built ND-100 PROG files)
Bootstrap embedded? No Yes (44 octal locations) No
Direct execution No (must be linked) Yes after @PLACE-BINARY Yes
Default file type :BRF :BPUN :PROG

Source: ND-60.066.04 sections 1.1.4 and 1.1.7; SINTRAN/OS/SEGMENTS-INTRO-AND-DEEP-DIVE.md table at line 1185-1187.

2. How a :PROG File Is Produced

There are four documented production paths:

2.1 NRL *DUMP (basic / image-file mode)

*DUMP <destination file name>[<start address><restart address>]
  • The currently loaded program (whatever the loader has linked into its work area or into an IMAGE-FILE) is written to <destination file name>.
  • Default file type if none is supplied: :PROG.
  • The recorded start address is where execution begins under @RECOVER.
  • The recorded restart address is where execution resumes under @CONTINUE. If the user does not specify them, the program's main entry is used for both.
  • The dumped extent defaults to the lowest through the highest address touched by the loader since the last RECOVER. The user can override this with *BOUNDARIES <lower> <upper>.

Source: ND-60.066.04 lines 505-523 and Appendix A line 1657.

2.2 NRL *PROG-FILE (prog-file loading mode)

*PROG-FILE <file name>
... loading commands ...
*EXIT
  • Must be the first loader command after entering NRL.
  • All subsequent *LOAD commands write directly to the named file in absolute binary form rather than into the loader's in-memory work area.
  • The last command must be *EXIT. (*DUMP and *BPUN are not allowed in this mode.)
  • Default file type: :PROG.
  • Resulting file is only executable via SINTRAN @RECOVER.

Source: ND-60.066.04 section 1.1.7, lines 571-577.

2.3 NRL *IMAGE-FILE followed by *DUMP

*IMAGE-FILE <file name>      ! file type defaults to :IMAG
... *LOAD ... *LOAD ...
*DUMP <prog file>
*EXIT
  • Used for very large programs whose linked image will not fit in the loader's memory work area.
  • The :IMAG file is a transient memory-image work file; the user then produces the deliverable :PROG from it with *DUMP.
  • *SET-LOAD-ADDRESS may now address from 0 upwards.

Source: ND-60.066.04 section 1.1.6, lines 557-569.

2.4 SINTRAN @DUMP from a running address space

@DUMP <file name>, <start>, <restart>
  • Captures the caller's current memory contents between the limits previously set by @MEMORY (or default boundaries) into a :PROG file.
  • Used, for example, to save a hand-modified MON image: change a default with the operator commands, leave the monitor with EXIT, then @DUMP the result. The new :PROG file is functionally equivalent to the original monitor but with the modified defaults baked in.
  • Permitted only for user SYSTEM in modern SINTRAN versions.

Source: Reference-Manuals/SINTRAN-COMMANDS-REFERENCE.md line 8801 and entry ### DUMP at line 2387; ND-60.047.03 NORD PL User's Guide line 3615.

2.5 NLL (ND-500 Loader Monitor) producing an ND-100 :PROG

When NLL is set with COMPUTER-MODE 100:

  • Default object file type changes to :BRF.
  • Code, data and debug information are placed on the :PSEG file but in the same on-disk format as an ordinary ND-100 :PROG file.
  • The :DSEG file is not used.
  • The resulting file is executed via NLL's $RECOVER.

Source: Reference-Manuals/ND-60.136.04A ND-500 Loader Monitor.md line 3140.

3. Logical Structure of a :PROG File

The published Norsk Data manuals describe the :PROG file operationally - they tell you what it must contain and how @RECOVER consumes it - rather than giving a byte-by-byte field layout the way the BRF chapter (chapter 2 of ND-60.066.04) does for :BRF. The fields below are the ones that the manuals explicitly require to be present. Field offsets that are not documented in the sources are marked UNVERIFIED.

3.1 Required logical fields (all variants)

Field Width Purpose Source
Start address 1 word (16 bits) Address loaded into the program counter on @RECOVER. Defaults to the program's main entry if *DUMP was issued without an explicit value. ND-60.066.04 line 511
Restart address 1 word Address used when the program is resumed with @CONTINUE. Defaults to the same value as the start address. ND-60.066.04 line 511
Lower bound 1 word Lowest virtual address covered by the dump. Set by *BOUNDARIES or by the lowest address the loader touched since the last RECOVER. ND-60.066.04 lines 511, 523
Upper bound 1 word Highest virtual address covered by the dump. as above
Memory image (upper - lower + 1) words The actual contents of the program's address space, in word order, from lower through upper inclusive. implicit from @RECOVER behaviour described in SEGMENTS-INTRO-AND-DEEP-DIVE.md lines 1389-1392

ASSUMPTION: the four control words above appear in a small fixed-format header at the start of the file, followed by the raw image. The manuals do not publish the order of the header words, only that all four pieces of information are stored in the file.

3.2 Additional fields for two-bank :PROG files

When the program was built in two-bank mode (separate code/program bank and data bank), *PROG-FILE or *DUMP records additional information needed by @RECOVER to populate the alternate page table:

Field Purpose Source
Data-bank file name Until the two-bank RECOVER is fully implemented in SINTRAN, the data bank contents are read back from the PROG file itself; the file therefore stores the file name (and optionally the user name) as supplied to the original *PROG-FILE or *DUMP command, so that @RECOVER can locate the right file when the user environment differs. ND-60.066.04 line 1011
Data-bank image The full 64KW (or BOUNDARIES-restricted) image of the alternate (data) bank. Loaded into the alternate memory bank by @RECOVER. ND-60.066.04 lines 1009-1015
Code-bank image The image of the program (code) bank. as above
(Optional) duplicated data area If the combined code+data fit inside one 64KW bank, the user may issue *DATA-BANK-COPY before the dump. The data area is then duplicated into the PROG segment above the code so that @RECOVER can initialise the data bank from the in-memory copy instead of re-reading the PROG file. ND-60.066.04 lines 1013-1015 and Appendix A line 1639

Note from the Loader manual: "One-bank and two-bank programs may not be mixed. The BPUN command does not apply to two-bank systems." (line 1007)

3.3 Optional fields produced by NLL in COMPUTER-MODE 100

When the file is produced by NLL with COMPUTER-MODE 100, the :PROG file may additionally contain debug information (sufficient for the ND-500 Symbolic Debugger's source-level facilities), in the same on-disk format as the :PROG produced by NRL but with the debug section appended on the :PSEG file. Sources do not document the layout of this debug section in field form.

Source: ND-60.136.04A line 3140. Layout details UNVERIFIED.

3.4 Reentrant program variant (@DUMP-PROGRAM-REENTRANT)

@DUMP-PROGRAM-REENTRANT <program_name> writes a reentrant program image to a :PROG file usable for rebuilding reentrant subsystems after a cold restart (typically driven from the HENT-MODE mode file together with DUMP-REENTRANT and DUMP-PROGRAM-REENTRANT commands).

Aspect Value
Permitted for User SYSTEM only
File type :PROG
Header fields Same as section 3.1
Additional payload Reentrant subsystem image (image-area + run segments). The image is consumed by @RECOVER style restoration during cold-start sequencing.

Source: Reference-Manuals/SINTRAN-COMMANDS-REFERENCE.md lines 1354 and 2538-2563.

4. How a :PROG File Is Consumed (@RECOVER)

@RECOVER <file> performs the following sequence (paraphrased from SINTRAN/OS/SEGMENTS-INTRO-AND-DEEP-DIVE.md lines 1389-1392 and ND-60.066.04 section 1.4.2):

  1. The PROG file's logical header is read; SINTRAN extracts the lower/upper bounds, start address and restart address.
  2. A background segment is allocated (or reused) for the calling RT description.
  3. The pages spanning [lower .. upper] of the segment are mapped into the user's PIT (Page Index Table).
  4. The memory image portion of the file is read directly into the mapped pages (the code bank).
  5. Two-bank only: the data-bank image is read either from the same PROG file, or from the file recorded inside the PROG header (see 3.2), into the alternate page table. If *DATA-BANK-COPY was used at dump time, @RECOVER instead initialises the data bank by copying from the duplicated area above the code in the PROG segment.
  6. The program counter is set to the start address and execution begins.
  7. A subsequent @CONTINUE will (re)start execution at the restart address instead.

@CONTINUE and @ABORT operate on the same in-memory image; the PROG file itself is not modified by execution.

5. Format Variants Summary

Variant Producer Banks Extra fields Consumer
Standard one-bank NRL *DUMP / *PROG-FILE, SINTRAN @DUMP 1 x 64KW none @RECOVER
Two-bank (split code/data) NRL two-bank mode + *PROG-FILE or *DUMP 2 x 64KW data-bank file name, alternate-bank image @RECOVER (with two-bank support)
Two-bank with DATA-BANK-COPY NRL two-bank mode + *DATA-BANK-COPY then *DUMP 2 x 64KW logically, single image physically data area duplicated above code @RECOVER (initialises data bank from in-segment copy)
Image-file derived *IMAGE-FILE then *DUMP 1 or 2 identical to the corresponding above variant @RECOVER
Reentrant program @DUMP-PROGRAM-REENTRANT 1 reentrant subsystem image payload Cold-start restore via HENT-MODE, then @RECOVER for use
NLL ND-100 mode NLL COMPUTER-MODE 100 1 optional ND-100 source-level debug section NLL $RECOVER
Hand-modified monitor Operator changes default, EXITs monitor, @DUMP 1 none @RECOVER

6. Relationship to :BPUN (for contrast)

:BPUN is the related but distinct absolute binary format produced by *BPUN (NRL) and )BPUN (MAC). It is not the same as :PROG:

  • A :BPUN file carries a 44 (octal) word bootstrap loader prefixed to the program image, so it can be loaded by the ND-100 hardware loader on a stand-alone machine, by the operating system, or by MAC's )9READ.
  • It carries an explicit start address (the program's main entry, in symbolic or octal form) and a bootstrap address (where the 44-word bootstrap will reside when loaded into a stand-alone NORD-10/ND-100).
  • A checksum is generated by )BPUN and verified by the loader.
  • It is loaded into a SINTRAN address space with @PLACE-BINARY, not @RECOVER.
  • :BPUN does not apply to two-bank systems.

Source: ND-60.066.04 lines 515-519 and Appendix A line 1637; ND-60.096.01 MAC ... User's Guide.md lines 2212-2216.

7. Known Gaps in the Public Documentation

Gaps 1 and 2 below are answered in the companion document prog-fileformat.md, from the NPL source of @RECOVER (RP-P2-MONCALLS.NPL, which reads exactly 7 words from block 0) and four real :PROG files: the header is 7 big-endian 16-bit words at file offset 0 - start, restart, bank 1 first/last, bank 2 first/last, data-bank-copy last - and there is no magic number or version word. The list is kept as written because it is still true of the MANUALS; gaps 3, 4 and 5 are still open, and the companion's own section 6 lists what it could not settle.

The following details are not published in the manuals in the repository and would require disassembly of NRL or of the SINTRAN @RECOVER / @DUMP command processors to verify:

  1. The exact byte/word offsets of the start, restart, lower-bound and upper-bound fields in the file header.
  2. Whether the header carries any magic number or version word (the manuals never refer to one).
  3. The on-disk encoding of the data-bank file name field used by two-bank PROG files (presumed packed in standard SINTRAN file-name form, but UNVERIFIED).
  4. The exact layout of the optional debug section appended by NLL in COMPUTER-MODE 100.
  5. Whether reentrant-program PROG files have additional descriptor words compared to ordinary one-bank PROG files.

If a definitive layout is required, the candidate sources to inspect inside this repository are:

  • SINTRAN/NPL-SOURCE/NPL/RP-P2-MONCALLS.NPL (RECOVER monitor call paths)
  • SINTRAN/NPL-SOURCE/NPL/PH-P2-OPPSTART.NPL (cold-start, image loading)
  • SINTRAN/NPL-SOURCE/NPL/5P-P2-MON60.NPL (MON 60 image handling)

These are listed in the file index SINTRAN/NPL-SOURCE/README.md.

8. Quick Reference Card

Produce
-------
NRL  *DUMP <file>[ <start> <restart>]            -> :PROG  (one or two bank)
NRL  *PROG-FILE <file> ; *LOAD ... ; *EXIT        -> :PROG  (direct, must be first cmd)
NRL  *IMAGE-FILE <file> ; ... ; *DUMP <prog>      -> :PROG  (large programs)
NRL  *DATA-BANK-COPY (two-bank, before *DUMP)     -> :PROG  (data area duplicated above code)
SIN  @DUMP <file>,<start>,<restart>               -> :PROG  (from current address space)
SIN  @DUMP-PROGRAM-REENTRANT <name>               -> :PROG  (reentrant variant, SYSTEM only)
NLL  COMPUTER-MODE 100 ; ... ; (writes :PSEG)     -> :PROG-format on :PSEG

Consume
-------
SIN  @RECOVER <file>          ! load and start at start address
SIN  @CONTINUE                ! resume at restart address
NLL  $RECOVER <file>          ! ND-100 mode, NLL-built PROG file

Boundaries / addresses
----------------------
NRL  *BOUNDARIES <lower> <upper>          ! override default dump extent
NRL  *SET-LOAD-ADDRESS <addr>             ! where subsequent code is placed
NRL  *SET-DATA-LOAD-ADDRESS <addr>        ! one-bank build of two-bank prog
NRL  *SET-MODE PROG | DATA                ! select bank for subsequent commands
SIN  @MEMORY <lower> <upper>              ! defines @DUMP extent

Last updated: 2026-04-09 Status: Phase 1 - operational reference complete. The byte-level header layout is NOT in this document; it was established from the NPL source and real files in prog-fileformat.md. (Status line corrected 2026-09-18; the body above is unchanged since 2026-04-09.)