Initial Commands and Automatic Startup in SINTRAN III¶

Scope: SINTRAN III VSX / VSX-500, ND-100/ND-110, versions K03 / L07 / M06 Purpose: Explain what SINTRAN runs automatically at start-up, where those commands live (MEMORY vs DISK), and exactly how to read/find them.

Notation: memory sizes in WORDS (1 word = 2 bytes). Octal written NNNNN₈. Every claim is tagged VERIFIED (from a manual, the symbol tables, the NPL source, or the actual system disk) or UNCERTAIN.

Cross-references (relative links): - 22-READING-RT-AND-SEGMENT-TABLES-FROM-MEMORY.md — live memory-read conventions - 19-MEMORY-MAP-REFERENCE.md — memory map - ../../Reference-Manuals/SINTRAN-COMMANDS-REFERENCE.md — command reference

0. Executive summary¶

There are two distinct startup mechanisms, and they work together:

Mechanism	Lives in	Set/edited by	Read by	Confidence
Initial-command buffer (a small list of commands, first must be `@ENTER-DIRECTORY`)	MEMORY — resident/segment-mapped buffer `INICO`; persisted inside the SINTRAN memory image on `SEGFIL0`	`@INITIAL-COMMAND`, `@NEXT-INITIAL-COMMAND`	`@LIST-INITIAL-COMMANDS`	VERIFIED
Mode / batch start-up files `HENT-MODE:MODE` (cold start) and `LOAD-MODE:MODE` / `LOAD-MODE:BATC` (warm start)	DISK — ordinary 7-bit command files on user `SYSTEM`	any editor (PED etc.)	`@LIST-FILES`, extract & read the file	VERIFIED

The in-memory initial-command buffer is tiny and runs first at restart. Its job is to enter the main directory and then hand off to the disk mode/batch files, which do the real work (start XMSG/COSMOS, TAD, spooling, set the system available, etc.).

The practical recipe: to see what runs automatically, look in both places — @LIST-INITIAL-COMMANDS (the memory buffer) and the HENT-MODE/LOAD-MODE files on disk (§4).

1. Terminology — what SINTRAN calls it¶

VERIFIED. SINTRAN III uses the term initial commands for the in-memory buffer, and mode files / batch files for the disk scripts.

Commands (all restricted to user SYSTEM):

Command	Function	Source
`@INITIAL-COMMAND <command string>`	Define the first initial command (must be `@ENTER-DIRECTORY`). Stored as the first entry of the initial-command buffer.	ND-60.128.5 Reference Manual, "@INITIAL-COMMAND"
`@NEXT-INITIAL-COMMAND <command string>`	Append a further command to the buffer.	ND-60.128.5, "@NEXT-INITIAL-COMMAND"
`@LIST-INITIAL-COMMANDS <output file>`	List the buffer contents (default output = terminal).	ND-60.128.5, "@LIST-INITIAL-COMMANDS"

"Specify the first command to be executed at next restart from memory image, @RESTART-SYSTEM, or pressing MASTER CLEAR and LOAD buttons. The command must be @ENTER-DIRECTORY. It is stored as the first command in the initial command buffer." — Reference-Manuals/ND-60.128.5 EN SINTRAN III Reference Manual.md:5340

"When @INITIAL-COMMAND has been issued, @RTENTER is automatically executed at subsequent restarts." — Reference-Manuals/ND-60.128.5 EN SINTRAN III Reference Manual.md:5355

So after @INITIAL-COMMAND is set once, @RTENTER no longer has to be issued by hand at every restart (also stated in Reference-Manuals/ND-60.050.06 SINTRAN III Users Guide.md:4799).

HENT is the Norwegian for "fetch/retrieve" — HENT-MODE is the "fetch/cold-start" mode file, LOAD-MODE the warm-start (load-from-image) file. VERIFIED by the consistent §1.6 "CHANGES TO THE HENT-MODE AND LOAD-MODE FILES" sections in the K/L/N release notes (e.g. SINTRAN/Release-Documentation/ND-860230-6-EN Sintran III - Release Information - L-Version.md:499).

2. The MEMORY structure — the initial-command buffer (`INICO`)¶

VERIFIED. The initial-command buffer is a named location in the SINTRAN file-system symbol space (FILSYS-SYMBOLS), symbol INICO:

Version	`INICO` address	Source
L07	`134620₈`	`SINTRAN/NPL-SOURCE/SYMBOLS/L07/FILSYS-SYMBOLS.SYMB.TXT:3525`
M06	`137255₈`	`SINTRAN/NPL-SOURCE/SYMBOLS/M06/FILSYS-SYMBOLS.SYMB.TXT:3634`

Neighboring symbols confirm this is command-line / command-buffer machinery:

L07: RCPOO=134516, INICO=134620, CLCOM=134657, ECLCO=134670, WNKER=134721
M06: CLHOM=137200, CLSND=137227, INICO=137255 (CL* = command-line handling)

(FILSYS-SYMBOLS.SYMB.TXT, sorted by address.)

2.1 Is it resident or segment-mapped?¶

VERIFIED (address range) / UNCERTAIN (exact segment): INICO sits at 134620₈/137255₈, i.e. inside the 26000₈–177777₈ segment-mapped region, not resident low core. In the VSX system-segment table this range is covered by the file-system and command segments:

Seg	Name	Range	Description
6	`S3FS`	`26000–177777`	File system segment (running)
3	`S3COM`	`30000–177777`	Command segment (running)
12	`S3FSV`	`26000–177777`	Initial file system segment (save image)
13	`S3OPCSV`	`26000–177777`	Initial command segment (save image)

— SINTRAN/Release-Documentation/ND-60230-5-EN SINTRAN III - Release Information - K-version.md:7882-7887

Because INICO is a FILSYS symbol, the live buffer is mapped in the file-system / command segment (S3FS/S3COM); its restart-surviving copy is held in the initial save segments (S3FSV / S3OPCSV, "Initial command segment"), which are written into the SINTRAN memory image on SEGFIL0 at @RESTART-SYSTEM / cold start. That is why the initial commands survive a restart even though they are a memory structure: the memory image is checkpointed to disk. This matches the manual: the commands run "at next restart from memory image". VERIFIED (mechanism), UNCERTAIN (whether INICO's home is segment 6 vs 3 precisely — both span the address).

2.2 CORRECTION (2026-07-10): the command text is at `INIBU`, not `INICO`¶

INICO is not the command-text buffer. It is a file-system symbol; the assumption that it held the buffer was an inference, now disproved. The initial-command text lives at the kernel symbol INIBU ("initial buffer") in the command segment:

Version	`INIBU`
K03	`067172`₈
L07	`074123`₈
M06	`102327`₈

Verified byte-exact against a live L07 system and two real SMD packs. The buffer can be read (and written) offline from a disk image, with no boot required: it sits inside the command segment's image in (SYSTEM)SEGFIL0:DATA, and its exact byte offset is derived from INIBU plus the segment table read off the same image.

Full specification, encoding, algorithm and golden test vectors: 26-INITIAL-COMMAND-BUFFER-ON-DISK.md

On a running system, @LIST-INITIAL-COMMANDS (§4.1) remains the easiest way to see them. The NPL command handler that fills INICO is not present in the NPL source subset in this repo (searching SINTRAN/NPL-SOURCE/NPL/ for INICO / INITIAL finds only unrelated matches); the symbol is known only from FILSYS-SYMBOLS. VERIFIED (absence in repo).

3. The DISK files — mode / batch start-up scripts¶

VERIFIED. The bulk of automatic startup is ordinary SINTRAN command files on user SYSTEM:

HENT-MODE:MODE — run after a cold start ()HENT, MACL+LOAD). Does one-time setup: @RTENTER, DUMP-REENTRANT, load ND-500 monitor, initialise XMSG, define memory config, etc. Referenced throughout the release notes' §1.6 and installation sections, e.g. SINTRAN/Release-Documentation/ND-860230-6-EN ... L-Version.md:503,781.
LOAD-MODE:MODE / LOAD-MODE:BATC — run after a warm start (restart from image). Re-applies things that do not survive a warm start (start batch processors, XMSG/COSMOS spooling, TAD administrator, set the system available). See §1.6 of the same release notes.

3.1 Actual `LOAD-MODE:MODE` from the system disk¶

VERIFIED by extraction from the live SINTRAN III VSX/500-L disk image (~/repos/nd100x/SMD0.IMG), file (SYSTEM)LOAD-MODE:MODE (entry [0037], 410 bytes, dated 1996-04-01). Extracted with ndtool -x -F 'SYSTEM/LOAD-MODE:MODE' and decoded from SINTRAN 7-bit (high-bit-set) text:

@ENTER SYSTEM,xxxxxx,,3200,,,

@CC Start all batch processors
@BATCH
@BATCH

@CC Start XMSG and COSMOS Spooling
@MODE XMSG-START:MODE,,,

@CC Start the TAD ADMinistrator
@START-TADADM

@CC Set the system available
@SET-AVAILABLE

@MAIL
@DIRECT-BROADCAST
SYSTEM IS AVAILABLE
@EXIT

@CC List routing to initialize all systems:
@(UTIL)XMSG-COMMAND
LIST-ROUTING,,,,,,
EXIT
@CC END OF FILE

This is the concrete "automatic startup command list" for this machine: it starts two batch processors, runs the XMSG-START:MODE sub-mode file (which brings up XMSG and COSMOS spooling), starts the TAD administrator, marks the system available, and broadcasts availability.

Note there is no plain-text file that stores the initial-command buffer; the buffer's persisted form lives inside the binary (SYSTEM)SEGFIL0:DATA memory image (entry [0002] on the same disk), not as a readable file. The readable startup scripts are the HENT-MODE / LOAD-MODE mode files above.

4. HOW-TO — see what is set up to run automatically¶

4.1 On a running system (the buffer)¶

From user SYSTEM:

@LIST-INITIAL-COMMANDS,,

Example real output (from ND-60.128.5:5814):

ENTER-DIRECTORY,,DISC-2-75MB,0
CONN SYS-OUT-1 105 R
CLOSE 105
BATCH
APPEND-BATCH 1 LOAD-MODE SYS-OUT-1

Here the buffer enters the directory and then chains into the disk LOAD-MODE file via APPEND-BATCH — showing the memory→disk hand-off directly.

4.2 On a running system (the mode files)¶

@LIST-FILES HENT-MODE:MODE,
@LIST-FILES LOAD-MODE,
@PLACE-BINARY ...   (or just open in PED / TYPE the file)

4.3 Offline, from the disk image (no boot required)¶

List and extract with the NDFS tool:

# list SYSTEM user files
~/repos/norskdata-ndfs/ndfs-c/build/ndtool -t -u SYSTEM ~/repos/nd100x/SMD0.IMG

# extract the warm-start mode file
~/repos/norskdata-ndfs/ndfs-c/build/ndtool -x -F 'SYSTEM/LOAD-MODE:MODE' -o /tmp/out ~/repos/nd100x/SMD0.IMG
# (also try HENT-MODE:MODE if present on the pack)

The extracted file is 7-bit with the high bit set — mask each byte with 0x7F to read it as ASCII (see §3.1).

4.4 The initial-command buffer from raw memory (rarely needed)¶

INICO = 134620₈ (L07) / 137255₈ (M06), in the file-system/command segment. Prefer §4.1; only decode INICO directly if @LIST-INITIAL-COMMANDS is unavailable and the file-system segment is mapped.

5. Sources¶

Reference-Manuals/ND-60.128.5 EN SINTRAN III Reference Manual.md — @INITIAL-COMMAND (5337-5360), @LIST-INITIAL-COMMANDS (5794-5823), @NEXT-INITIAL-COMMAND (6837+), "initial command buffer"
Reference-Manuals/ND-60.050.06 SINTRAN III Users Guide.md:4799,5436,5448-5454 — @INITIAL-COMMAND and @RTENTER behavior
Reference-Manuals/SINTRAN-COMMANDS-REFERENCE.md:3212,3568 — INITIAL-COMMAND / LIST-INITIAL-COMMANDS
SINTRAN/NPL-SOURCE/SYMBOLS/L07/FILSYS-SYMBOLS.SYMB.TXT:3525 — INICO=134620
SINTRAN/NPL-SOURCE/SYMBOLS/M06/FILSYS-SYMBOLS.SYMB.TXT:3634 — INICO=137255
SINTRAN/Release-Documentation/ND-60230-5-EN ... K-version.md:7882-7887 — system-segment table incl. S3OPCSV "Initial command segment"
SINTRAN/Release-Documentation/ND-860230-6-EN ... L-Version.md:499-513,781 — §1.6 HENT-MODE / LOAD-MODE, cold vs warm
System disk ~/repos/nd100x/SMD0.IMG, (SYSTEM)LOAD-MODE:MODE extracted via ndtool (§3.1)

Last updated: 2026-07-09 Status: VERIFIED where tagged; two UNCERTAIN points noted (exact home segment of INICO; NPL handler not in repo subset)