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3B SetEcho

Validated   MON 3B (3 decimal) · Mnemonic ECHOM · Group: Input and Output Monitor Calls (manual section 2.5)

Available from: All programs (manual compatibility box)

Emulation source: src/handlers/mon_3B_SetEcho.c

Description

When you press a key on the terminal, a character is normally displayed. This is called echo. You modify a terminal's echo with this monitor call.

  • If 8-bit I/O is set (TerminalFunction, function number 112), you will get echo always if bit 7 in the echo table is set.

Parameters

Name Type Direction Description
DeviceNumber INTEGER2 In The terminal's logical device number. See appendix B. Only needed for RT programs. Background programs ignore this parameter. The user's terminal is assumed.
EchoStrategy INTEGER2 In Echo strategy: <0=No echo, 0=Echo all, 1=Echo except control chars, 2=MAC echo, 3-6=System defined, 7=User-defined table.
Table INTEGER2[8] In User-defined echo table (128 bits for ASCII chars). Only used when EchoStrategy=7. Bit 0 means echo that character.

Direction: In = the program supplies the value, Out = the call returns it, In/Out = both.

See also

SetBreak

Compatibility

Machines Users Programs
ND-100 and ND-500 All users All programs

The manual's compatibility box for this call, word for word.

Yes/no fields from the YAML extraction (not in the manual's words):

ND-100 ND-500 User programs RT programs System programs
No No Yes Yes No

Disagreement

The manual box says ND-100 and ND-500, but the yes/no fields say ND-100 = No, ND-500 = No. The manual box is the source.

Examples

From the manual (OCR text, not corrected).

INTEGER : DeviceNumber, EchoStrategy
INTEGER2ARRAY{0:7}
...
Monitor_Call('SetEcho', DeviceNumber, EchoStrategy, Table(0))

INTEGER DeviceNumber, EchoStrategy
INTEGER Table(8)
...
Monitor_Call('SetEcho', DeviceNumber, EchoStrategy, Table(1))

DeviceNumber, EchoStrategy : INTEGER2;
Table : RECORD...END;
...
SetEcho(DeviceNumber, EchoStrategy, Table);

01 DeviceNumber COMP.
01 EchoStrategy COMP.
01 Table.
  02 array COMP OCCURS 8 TIMES.
  ...
MONITOR-CALL "SetEcho" USING DeviceNumber, EchoStrategy, Table.

DeviceNumber : W BLOCK 1
EchoStrategy : W BLOCK 1
Table : H BLOCK 8
SetEcho : EQU 37B9 + 3B
...
CALLG SetEcho, 3, DeviceNumber, EchoStrategy, Table

LDT DEVNO  %Logical device number.
LDA STRAT  %Echo strategy.
LDX (TABLE %Eight word large bit map.
MON 3      %Monitor call SetEcho.
...
DEVNO, ...
STRAT, ...
TABLE, ...
*+10/ %Make a buffer of 8 words.

ndmonlib implementation

Validated Registered MON_STATUS_VALIDATED in src/core/mon_registry.c: implemented, tested and working.
Handler mon_3B_SetEcho
Code lines 38 (non-blank, non-comment lines in the file)

Emulation research

Source

This section comes from the emulation: block of the call's YAML file in the NDInsight repo. It records what was learned while implementing the call in nd500x; its status is nd500x's, not ndmonlib's.
Status (nd500x) implemented
nd500x handler nd500x/src/libmon/handlers/mon_3B_SetEcho.c
Last updated 2026-07-17

Echo strategies

  • Radix: decimal
  • Note: The strategy codes as nd500x implements them (mon_terminal_state.h / mon_503B_InputString.c should_echo_char_ex). Strategies 3-6 are a documented gap - see unverified.

  • Codes

    Code Name Description Status
    -1 ECHO_STRAT_NONE Negative = no echo; characters are not displayed. implemented
    0 ECHO_STRAT_ALL Echo all characters. implemented
    1 ECHO_STRAT_NO_CONTROL Echo except control characters. nd500x tests ch >= 32 && ch < 127. implemented
    2 ECHO_STRAT_MAC MAC echo strategy - printable characters plus CR and LF. implemented
    7 ECHO_STRAT_USER User-defined 128-bit table read from the Table parameter (4 x 32-bit words). implemented

Parameter notes

Name Note Verified
Table Read as 4 consecutive 32-bit words from arg_addresses[2] (128 bits) when strategy is 7. On ND-500 these are W, not H. Yes
EchoStrategy Read as a signed 32-bit word - the strategy is meaningfully negative. Yes

Verified

1. THE ECHO TABLE HAS INVERTED SEMANTICS FROM THE BREAK TABLE: bit = 0 means ECHO, bit = 1 means DO NOT echo. (The break table is the natural way round: bit = 1 means break.) This is a real trap - the two 128-bit tables look identical and are not.

Field Value
Evidence nd500x/src/libmon/handlers/mon_503B_InputString.c should_echo_char_ex(): "INVERTED: bit=0 means echo, bit=1 means don't echo" -> return !bit_table_test_bit(user_table, ch); versus is_break_char_ex() -> return bit_table_test_bit(user_table, ch).

2. The state 3B sets is REAL per-device state, consumed by the input calls: a later 503B DVINST / 511B DVIO with no per-call EchoStrat argument falls back to mon_get_echo_strategy(device).

Field Value
Evidence mon_503B_InputString.c mon_dvinst_read(): echo_strat = (ctx->arg_count > 5) ? read arg 5 : mon_get_echo_strategy(device_no).

Unverified

  • STRATEGIES 3-6 (the manual's "system-defined tables") ARE NOT IMPLEMENTED. nd500x silently falls through to a PLACEHOLDER (echo all except control characters). The actual system tables are not in the scanned pages and no traced program selects 3-6.
  • Strategy 8 ("last user-defined table") is handled for BREAK (4B/503B) but there is no ECHO_STRAT_LAST_USER path proven by any caller.
  • The manual's note "If 8-bit I/O is set (TerminalFunction, function number 112), you will get echo always if bit 7 in the echo table is set" IS modelled in the 503B input path (should_echo_char_ex, eight_bit_io && ch >= 128 -> test bit 7), but the 8-bit I/O flag itself is never set by any traced program, so that path has never executed.
  • NO OBSERVED CALLER. No traced program (NC, CAT-500, ND linker) issues 3B. Echo behaviour reaches the emulator instead through the per-call EchoStrat argument of 503B/511B.

Sources

Doc Note
SINTRAN III Monitor Calls (ND-860228.2 EN) The manual body of this YAML.

Source

SINTRAN III Monitor Calls (ND-860228.2 EN), page 441.