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MON 256B (octal) - FullFileName (DEABF)

Returns a complete file name from an abbreviated one - the directory, the user, the file name, the file type, and the version are all returned. The caller passes the abbreviated name, a receive buffer, and a default file type (ND-100 only). The abbreviation must be unambiguous and the caller needs read access.

The NC disassembler labels MON 256B "FNAME"; the authoritative name is FullFileName, worker mnemonic DEABF ("de-abbreviate file"), which matches the FILSYS worker symbol.

Status: GOTAB dispatch head byte-proven (GOTAB[256B] = 066256B, the F1735 level-14 stub in 025-S3IRPIT); the DEABF worker body is real SINTRAN L bytes and de-abbreviates the name via the file-system primitives (FLPAR, USCPS, SUCPS, GFILN, MDEAB, CHDUO, CPTYP); the exact MON 256 -> worker link crosses an uncarved kernel bridge (see Honest caveats). All addresses/values are octal.

Dispatch path

flowchart LR
    A["User program<br/>MON 256B"] --> B["ENT14 level-14<br/>T = MON number"]
    B --> C["GOTAB[256B] = 066256B<br/>(byte-proven)"]
    C --> D["F1735 entry stub<br/>025-S3IRPIT :66256B"]
    D -.uncarved CALLPROC.-> E["DEABF de-abbreviate-file worker<br/>006-S3FS :111015B"]
    E --> F["FLPAR / USCPS / SUCPS / GFILN<br/>MDEAB / CHDUO / CPTYP"]
    class A blue
    class B,C,D teal
    class E,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

The dashed hop (D -> E) is the resident CALLPROC/segment-switch - it is not present in any carved segment, so it is the one link that cannot be followed statically.

Code location (dispatch path)

Every row is a real region you can open. The byte offset is the authoritative decimal byte offset from the segment .hex (the 025-S3IRPIT carve has an unmapped hole before the stub, so its offset is not the plain (addr - loadbase) x 2).

Role Segment (full disasm) Addr range (octal) Byte offset Symbol Verdict
GOTAB[256] dispatch word commoncode.asm - .hex 071511B (1 word) 59026 GOTAB+256 = 066256B VERIFIED
F1735 entry stub 025-S3IRPIT.asm - .hex 66256B-66261B (4w) 29020 F1735 VERIFIED
resident CALLPROC bridge - (uncarved) - - CALLPROC UNVERIFIED
DEABF worker body 006-S3FS.asm - .hex 111015B-111207B (code to 111165B) 52250 DEABF real bytes; link MISATTRIBUTED

Verify by hand: grep '^111015 ' ../../segments-ref/006-S3FS/006-S3FS.hex -> byte offset 52250; then dd if=../../../segments/006-S3FS.bin bs=1 skip=52250 count=8 | od -An -tx1 -> f8 10 22 68 cc 65 cc 59 (= octal 174020 021150 146145 146131 = BSET ZRO SSK / STD I 150 / RADD CLD SL DA / RADD CLD SB DD, the DEABF entry).

The GOTAB slot itself: dd if=../../../resident/SINTRAN-DATA_commoncode.bin bs=1 skip=59026 count=2 | od -An -tx1 -> 6c ae (big-endian word = 066256B).

The F1735 stub: grep '^66256 ' ../../segments-ref/025-S3IRPIT/025-S3IRPIT.hex -> byte offset 29020; then dd if=../../../segments/025-S3IRPIT.bin bs=1 skip=29020 count=2 | od -An -tx1 -> 0c fb (= 006373B, the F1735 entry).

Instruction walkthrough

Full listing: 256B-FullFileName.ASM. Two regions:

Region A - F1735 entry stub (66256-66261, 025-S3IRPIT) is the 4-word level-14 entry vectored from GOTAB[256], bounded strictly to the next symbol F1737 = 66262B. It runs a short prologue (66256 STA ,X -5, 66257 ION, 66260 LDA ,B 20) and ends in 66261 EXIT (return); it does not itself branch to the DEABF worker - that transfer is the uncarved resident CALLPROC hop.

Region B - DEABF worker (111015-111165, 006-S3FS; link cells 111166-111207) is the functional body. All calls to shared file-system workers are indirect (JPL I / JMP I) through the pointer table at 111166-111207; those words are data (link cells), not code, and their resolved worker addresses are annotated in the .ASM.

  • Entry prologue (111015-111022) - 111015 BSET ZRO SSK clears the skip flag; 111016 STD I 150 stashes the caller's double-word; 111021 SAB 165 builds the large local frame B; 111022 JPL I 145 -> 003752 is the resident prologue worker.
  • Default-type branch (111023-111051) - 111023 BSKP ONE SSK selects whether a default file type was supplied. The no-default path sets the user context (111034 JPL I 136 -> USCPS, 31075), parses the abbreviated name (111041 JPL I 133 -> FLPAR, 46231), and copies the type (111051 JPL I 125 -> CPTYP, 30205).
  • Match / directory-user resolve (111052-111145) - 111064 JPL I 114 -> MDEAB (61044, match-de-abbreviated); the alternate path re-parses via USCPS/FLPAR, then checks the directory-user with 111133 JPL I 51 -> CHDUO (101303) and fetches the resolved name with 111137 JPL I 46 -> GFILN (60600, get-file-name); 111145 JPL I 41 -> SUCPS (31072) restores the user context.
  • Exit (111147-111165) - the normal path takes 111150 SAA -165 and returns through 111151 JMP I 36 -> 003776 (resident return). The ambiguity path (111152-111163) loads error number 113 (SAA 113). 111164 STA ,B 2 stores the status word into the caller's status slot B+2, and 111165 funnels into the resident return.

The calls to FLPAR, USCPS/SUCPS, MDEAB, CHDUO, GFILN and CPTYP are the byte-level reason DEABF is the FullFileName worker - it de-abbreviates a file name into directory / user / name / type / version exactly as the manual describes.

Parameter / register contract

Reg / field Dir Meaning Verdict
entry point (stub) in 66256B = F1735, the GOTAB[256] level-14 stub VERIFIED (bytes)
entry point (worker) in 111015B = DEABF worker entry VERIFIED (bytes)
SSK internal default-type selector; cleared at entry 111015, tested at 111023 VERIFIED (bytes)
D (double) in caller parameter, saved first (STD I 150) VERIFIED (copy); layout inferred
local frame B internal SAB 165 = 165B-word working frame VERIFIED (bytes)
X (manual) in address of the abbreviated file-name string (64 chars) inferred (manual MAC example)
A (manual) in/out in: address of the receive buffer; out: error number inferred (manual)
T (manual) in address of the default file type string (ND-100 only) inferred (manual)
error 113 out ambiguity / not-found literal (SAA 113 at 111163) VERIFIED (bytes); mapping inferred
B+2 out returned status word (STA ,B 2 at 111164) VERIFIED (bytes)

The user-visible X/A/T register convention lives in the caller-side MON 256 wrapper and the uncarved CALLPROC frame, so the precise user-register-to-field assignment is inferred from the manual, not byte-proven here. The error literal 113 is VERIFIED in the code; its mapping to the SINTRAN error-code table is UNVERIFIED.

Pseudo-code (for an emulator)

See 256B-FullFileName.pseudo.c - a pseudo-C model of the handler for emulator authors. Control flow + the calls to the file-system primitives are byte-verified; the parse/match semantics and error meaning are inferred from the call structure and the manual. Every instruction is translated per the canonical ND100-INSTRUCTION-SEMANTICS.md.

Honest caveats

What is byte-proven: GOTAB[256B] = 066256B (level-14 dispatch); the F1735 stub at 66256B in 025-S3IRPIT is real code (4 words, ending in EXIT); the DEABF worker body at 111015B in 006-S3FS is real code (entry bytes 174020 021150 146145 146131 match the disassembly); and it belongs to the file-name family - it calls FLPAR, USCPS/SUCPS, MDEAB, CHDUO, GFILN and CPTYP.

What is NOT proven: the link from the F1735 stub (in 025-S3IRPIT) to the DEABF worker (in 006-S3FS). The value 111015 occurs nowhere the stub dereferences; the stub returns via EXIT, and the stub->worker transfer is the resident CALLPROC/segment switch in an uncarved overlay. So the MON 256 -> DEABF attribution rests on the DEABF symbol name + its de-abbreviation calls + the matching behaviour, not a followed pointer - hence MISATTRIBUTED in the strict sense. Confirming it needs a live trace: break at 66256B on a real MON 256, single-step the segment switch, and confirm P lands on DEABF = 111015.

Region-B bound: the DEABF worker is bounded strictly to the next FILSYS symbol FOBJN = 111210B. Code runs 111015-111165; 111166-111207 are the pointer table (link cells). Every direct branch lands inside 111015-111165.

The link-cell content 020274 and 003752 / 003776 match no FILSYS-SYMBOLS entry; their low addresses suggest resident-monitor / save-restore routines outside the file-system segment and are not resolved here.

Method: ../../../../../EXTRACTING-RESIDENT-CODE.md - dispatch reality: ../../TASK-05-mismatches.md - master map: ../../MON-CALL-INDEX.md.