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MON 321B (octal) - UEADM (UEAdministrator)

Handle User Environment (administrator) - manual section 2.14, short name UEADM. A companion to MON 320B UELogin (UELOG) and MON 317B ExecuteCommand (UECOM), all in the same User-Environment code cluster.

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

CORRECTED 2026-07-13. The previous version of this folder said the worker was not-carved / name-only, "zero-filled", with GOTAB[321B]=112376B vectoring to a diagnostic region DIA6. All of that was an artefact of the wrong dispatch model. MON calls are not dispatched through that GOTAB (it is MFELL for 224 of 256 calls); they go through MCTAB @ 005620B. MCTAB[321B] = 065453B = UEADM, and that worker IS carved - in 003-S3CP, the same segment as its siblings UECOM/UELOG/SETOL. The old analysis read 065453B in SINTRAN-DATA_commoncode (zeros there - wrong overlay) and wrongly concluded "absent". See ../317B-ExecuteCommand/README.md and SINTRAN/CARVING-HANDOFF.md section 3a.

Dispatch path

flowchart LR
    A["User program<br/>MON 321B"] --> B["ENT14 level-14<br/>026-S3IMPIT :072167B"]
    B --> C["GOTAB[321B] = MFELL<br/>:071554B"]
    C --> D["MFELL level switch<br/>:072114B -> CALLP 032201B"]
    D --> E["MCTAB[321B] = UEADM<br/>044-S3IDPIT :006141B = 065453B"]
    E --> F["UEADM worker<br/>003-S3CP :065453B"]
    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[321B] slot 044-S3IDPIT.asm 006141B = 065453B 2242 -> UEADM VERIFIED
UEADM worker body 003-S3CP.asm 065453B-065642B 30294 UEADM VERIFIED

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

dd if=044-S3IDPIT.bin bs=1 skip=2242  count=2 | od -An -tx1   ->  6b 2b   (= 065453B = UEADM)
dd if=003-S3CP.bin    bs=1 skip=30294 count=2 | od -An -tx1   ->  cc 5f   (= 146137B, UEADM entry)

Instruction walkthrough

Full listing: 321B-UEAdministrator.ASM.

Prologue (065453B-065460B). Saves the parameter/frame base (X := B, stored at ,B -166) and the return link (L, stored at ,B -167).

Sub-function decode (065461B-065474B). Loads a selector from param[12] (LDA ,X 12) and range-checks it against [1..8] (SAT 1 / SKP IF DA GRE ST ... SAT 10 / SKP IF DT LST SA). Out of range -> stores error code 124B into param[12] and takes the error/return path.

User-table access (065475B-065534B). Stages the in-range operands, calls a helper via JPL I 111 (pointer @065620B), then computes an index (MPY 74 / ADD I 74) and does a physical read of a user-table entry (LDT I 73 / LDATX).

Bit-field extraction (065515B-065524B). Pulls two fields out of param[17] (SHA ZIN SHR 7 / AND 103 and SHA ZIN SHR 13 / AND 77) into frame slots.

Selector jump table (065600B-065612B). RADD SA DP computes P := P + selector, i.e. a computed dispatch into a small vector of JMP/JMP I per sub-function, using the pointer table at 065615B-065640B. The common tail reloads the saved registers at 065641B and returns.

The exact semantics of each of the 8 sub-functions are inferred from structure; only the control flow and the physical user-table read are byte-proven.

Parameter / register contract

Reg / field Dir Meaning Verdict
B / param base in frame/parameter block base (saved X := B, STX ,B -166) VERIFIED (bytes)
param[12] in/out sub-function selector, range-checked [1..8]; on error set to 124B VERIFIED (bytes)
param[17] in packed bit-fields extracted at 065515B-065524B VERIFIED (bytes); field meaning inferred
param[10],param[32],param[44] in staged operands for the selected sub-function VERIFIED (bytes); meaning inferred
return out via saved link ,B -167; common tail at 065641B VERIFIED (bytes)
caller class in system programs (manual: administer per-user User Environment) inferred (manual)

Pseudo-code (for an emulator)

See 321B-UEAdministrator.pseudo.c - the prologue, the selector range-check, the physical user-table read and the computed jump table are byte-verified; the per-sub-function semantics are inferred.

Honest caveats

What is byte-proven: MCTAB[321B] = 065453B = UEADM; the UEADM entry bytes at 065453B in 003-S3CP match the disassembly; the routine is a real ~100-word handler that decodes an 8-way sub-function selector from param[12], reads a per-user table by physical address (LDATX), and dispatches through a computed jump table.

What is NOT proven: the meaning of each of the 8 sub-functions, the exact layout of the user table it reads, and the manual's claim that 321B is "no longer supported" (section 2.16) - the carved bytes show a live, complete handler, which does not obviously match a retired call. That tension is noted, not resolved.

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