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MON 143B (octal) - RSIO (ExecutionInfo)

Returns information about how the calling program is executing: the execution mode (0 = interactive, 1 = batch, 2 = mode job, 3 = RT), the command-input device, the command-output device, and the owner's directory + user index. ND-100 monitor call.

Status: byte-verified (dispatch + worker body). The worker is real carved code in 003-S3CP, alongside its siblings GBGSZ / MBECH. All addresses/values are octal.

CORRECTED 2026-07-13. The previous version of this folder located the worker via a fictional level-14 GOTAB/F1670 compiler stub and read RSIO from SINTRAN-DATA_commoncode. MON calls are not dispatched through that GOTAB (it is MFELL for 224 of 256 calls); they go through MCTAB @ 005620B (segment 044-S3IDPIT). MCTAB[143B] = 051430B = RSIO, and that worker is carved in 003-S3CP. See ../317B-ExecuteCommand/README.md and SINTRAN/CARVING-HANDOFF.md section 3a.

Dispatch path

flowchart LR
    A["User program<br/>MON 143B"] --> B["ENT14 level-14<br/>026-S3IMPIT :072167B"]
    B --> C["GOTAB[143B] = MFELL<br/>:071376B"]
    C --> D["MFELL level switch<br/>:072114B -> CALLP 032201B"]
    D --> E["MCTAB[143B] = RSIO<br/>044-S3IDPIT :005763B = 051430B"]
    E --> F["RSIO worker<br/>003-S3CP :051430B"]
    class A blue
    class B,C,D,E teal
    class F green
    classDef blue fill:#E3F2FD,stroke:#0D47A1,color:#0D47A1
    classDef teal fill:#E0F7FA,stroke:#00838F,color:#00838F
    classDef green fill:#E8F5E9,stroke:#2E7D32,color:#2E7D32

Code location (dispatch path)

Byte offset = (addr - loadbase) in octal words x 2 (decimal). Offsets reproduced with dd.

Role Segment Addr (octal) Byte offset Symbol Verdict
MCTAB[143B] slot 044-S3IDPIT.asm 005763B = 051430B 2022 -> RSIO VERIFIED
RSIO worker body 003-S3CP.asm 051430B-051451B 17968 RSIO VERIFIED

Verify by hand (from tools/sintran-segment-carver/versions/L-VSX-500/segments/): 

dd if=044-S3IDPIT.bin bs=1 skip=2022  count=2 | od -An -tx1   ->  53 18   (= 051430B = RSIO)
dd if=003-S3CP.bin    bs=1 skip=17968 count=2 | od -An -tx1   ->  cc 59   (= 146131B, RSIO entry)

Instruction walkthrough

Full listing: 143B-ExecutionInfo.ASM.

RSIO saves the frame/param base (D := B), switches B to a work base (B := A), then selects one of two info sources based on a flag (JAF on ,B -103): either a direct field (,B -147) or an alternate value chased through a per-program table (LDX ,B -146 then mem[x+12], mem[x+23]). It restores the param base (B := D) and returns the result through EXIT (051451B). Control flow and the base/table access are byte-proven; the mapping of each field to mode / cmd-device / dir+user is inferred.

Parameter / register contract

Reg / field Dir Meaning Verdict
B (param base) in frame/parameter base, saved into D on entry VERIFIED (bytes)
A in work base loaded into B VERIFIED (bytes)
mem[,B -103] flag in selects direct vs table-chased info source VERIFIED (bytes)
result (A/D) out packed execution info (mode / cmd-in / cmd-out / dir+user) VERIFIED (returned); field layout inferred
execution mode / devices / dir+user index out the documented four values inferred (manual)

Pseudo-code (for an emulator)

See 143B-ExecutionInfo.pseudo.c - the base swap, the two-way source select and the EXIT are byte-verified; the field meanings are inferred from the manual.

Honest caveats

What is byte-proven: MCTAB[143B] = 051430B = RSIO; the RSIO entry bytes at 051430B in 003-S3CP match the disassembly; the routine reads one of two execution-info sources (a direct frame field or a table-chased value) and returns it via EXIT.

What is NOT proven: exactly which of mode / command-input device / command-output device / directory+user index maps to ,B -103, ,B -147, ,B -146 and the chased offsets 26/12/23. The old "F1670 stub + commoncode worker" model was the wrong dispatch table/overlay and is withdrawn.

Method: ../../../../../EXTRACTING-RESIDENT-CODE.md · master map: ../../MON-CALL-INDEX.md.