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MON 243B (octal) - GetDirNameIndex (FDINA)

Gets a directory index and a name index from a directory name string (1-16 characters, e.g. PACK-TWO). The name index identifies the device description of the disk that holds the directory. GetNameEntry (MON 245B) then reads the device's name entry from this name index.

Status: GOTAB dispatch head byte-proven as fall-through (GOTAB[243B] = 000000, no per-call stub); the FDINA worker body is real SINTRAN L bytes and resolves the directory via GDIRI (Get DIRectory Index) after parsing the name string with FLPAR; the exact MON 243 -> worker link crosses an uncarved kernel bridge (see Honest caveats). All addresses/values are octal.

Dispatch path

flowchart LR
    A["User program<br/>MON 243B"] --> B["ENT14 level-14<br/>T = MON number"]
    B --> C["GOTAB[243B] = 000000<br/>(byte-proven: fall-through)"]
    C -.uncarved MFELL / CALLPROC.-> E["FDINA get-dir-name-index worker<br/>006-S3FS :106734B"]
    E --> F["GDIRI get-directory-index<br/>006-S3FS :47402B"]
    E --> G["FLPAR name-string parse<br/>006-S3FS :46231B"]
    class A blue
    class B,C blue
    class E,F,G 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 GOTAB slot is zero, so there is no per-call entry stub. The dashed hop (C -> E) is the resident MFELL/CALLPROC fall-through second-level dispatch - 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. Byte offset = (addr - loadbase) in octal words x 2.

Role Segment (full disasm) Addr range (octal) Byte offset Symbol Verdict
GOTAB[243] dispatch word commoncode.asm - .hex 071476B (1 word) 59004 GOTAB+243 = 000000 VERIFIED (fall-through)
resident MFELL/CALLPROC bridge - (uncarved) - - CALLPROC UNVERIFIED
FDINA get-dir-name-index worker 006-S3FS.asm - .hex 106734B-107105B (to WDIEN) 50104 FDINA real bytes; link MISATTRIBUTED
GDIRI get-directory-index 006-S3FS.asm - .hex 47402B (call target) - GDIRI called by FDINA (link cell 107070) - VERIFIED
FLPAR name-string parse 006-S3FS.asm - .hex 46231B (call target) - FLPAR called by FDINA (link cell 107065) - VERIFIED

Verify by hand: grep '^106734 ' ../../segments-ref/006-S3FS/006-S3FS.hex -> byte offset 50104; then dd if=../../../segments/006-S3FS.bin bs=1 skip=50104 count=8 | od -An -tx1 -> f8 10 22 53 cc 65 cc 59 (= octal 174020 021123 146145 146131 = BSET ZRO SSK / STD I 123 / RADD CLD SL DA / RADD CLD SB DD, the FDINA entry).

The GOTAB slot itself: dd if=../../../resident/SINTRAN-DATA_commoncode.bin bs=1 skip=59004 count=2 | od -An -tx1 -> 00 00 (= 000000, fall-through).

The GDIRI link cell: dd if=../../../segments/006-S3FS.bin bs=1 skip=50288 count=2 | od -An -tx1 -> 4f 02 (= octal 047402, the word at 107070B = the resolved GDIRI worker address).

Instruction walkthrough

Full listing: 243B-GetDirNameIndex.ASM. The functional body is the FDINA worker; there is no F16xx stub because GOTAB[243] = 0. All calls to shared file-system workers are indirect (JPL I / JMP I) through the pointer table at 107060-107105. nd100-dis renders those pointer words as bogus instructions - they are data (link cells), not code; their contents are the real worker addresses (resolved in the .ASM).

  • Entry prologue (106734-106741) - 106734 BSET ZRO SSK clears the mode flag; 106735 STD I 123 stashes the caller's double-word parameter; 106740 SAB 75 builds the 75-word local frame B; 106741 JPL I 120 -> 003752 is the shared resident prologue worker.
  • Parse the directory name (106750-106762) - 106755 JPL I 106 -> 031075 (USCPS) and 106762 JPL I 103 -> 046231 (FLPAR, parameter parse) parse and validate the directory name string.
  • Resolve directory + name index (106764-107032) - 106770 JPL I 77 -> 010500 is a resident helper; 106773 JPL I 75 -> 047402 (GDIRI, Get DIRectory Index) yields the directory index; 107001 JPL I 72 -> 050124 (GDIRT, directory table) and 107010 JPL I 66 -> 061451 (REMCH, remote-char) resolve the remote/name case; 107030 JPL I 52 -> 054527 (GMUSI), 107032 JPL I 51 -> 054341 (GDFKN) and 107045 JPL I 40 -> 055263 (GDEFD) reach the name/device tables.
  • Return the indices (107034-107057) - the directory index goes to B+1 (107034 STT ,B 1) or B+2 (107050 STX ,B 2); 107036 MIN ,B 4 is the success return-link bump; the store-status point 107035/107052/107056 STA ,B 2 writes the result word into the caller's status slot B+2; every path funnels into the resident return 107040 JMP I 44 -> 003776.

The JPL I 75 call to GDIRI (link cell 107070 = 047402) plus the JPL I 103 call to FLPAR (link cell 107065 = 046231) are the byte-level proof that FDINA is the GetDirNameIndex worker: it parses a directory name and resolves the directory index (and the name/device index alongside it). FDINA (Find-DIrectory-NAme) is also the 243B short name in the manual.

Parameter / register contract

Manual-side names/types are from 243B_GetDirNameIndex.yaml.

Reg / field Dir Meaning Verdict
entry point (worker) in 106734B = FDINA worker entry VERIFIED (bytes)
SSK (skip flag) internal 0 at entry; latched to B+74 VERIFIED (bytes)
D (double) in caller parameter block, saved first (STD I 123) VERIFIED (copy); layout inferred
local frame B internal SAB 75 = 75B-word working frame VERIFIED (bytes)
X (manual) in address of the directory name string (1-16 chars) inferred (manual MAC example)
T (manual) out directory index (STT DIRIX) inferred (manual)
A (manual) out name index (STA NAMIX); error number on error return inferred (manual)
B+1 internal directory index result (STT ,B 1 at 107034) VERIFIED (bytes)
B+2 out returned status / index word (STA ,B 2 / STX ,B 2) VERIFIED (bytes)

The user-visible X in / T+A out register convention lives in the caller-side MON 243 wrapper and the uncarved MFELL/CALLPROC frame, so the precise user-register-to-field assignment is inferred from the manual, not byte-proven here.

Pseudo-code (for an emulator)

See 243B-GetDirNameIndex.pseudo.c - a pseudo-C model of the handler for emulator authors. Control flow + the calls to GDIRI / FLPAR / GDIRT are byte-verified; the parameter-field semantics and error-number meanings are inferred from the call structure and the manual. Every instruction is translated per the canonical ND100-INSTRUCTION-SEMANTICS.md (bare LDA disp = mem[P+disp]; RADD CLD SD DA = A = D; MIN ,B 4 success bump).

Honest caveats

What is byte-proven: GOTAB[243B] = 000000 (level-14 fall-through, no per-call vector); the FDINA worker body at 106734B in 006-S3FS is real code (entry bytes 174020 021123 146145 146131 match the disassembly, bounded by the next FILSYS symbol WDIEN = 107106B); and it resolves the indices - it calls FLPAR (046231B, link cell 107065) to parse the name and GDIRI (047402B, link cell 107070) to get the directory index.

What is NOT proven: the link from the zero GOTAB slot to the FDINA worker. Because the vector is zero there is no stub to disassemble and no pointer to dereference; dispatch drops into the resident MFELL/CALLPROC second-level path, which lives in an uncarved overlay. So the MON 243 -> FDINA attribution rests on the FDINA symbol name (the 243B short name) + its FLPAR/GDIRI calls + the matching resolve-directory-name behaviour, not a followed pointer - hence MISATTRIBUTED in the strict sense. Confirming the link needs a live trace: issue a real MON 243, single-step the level-14 fall-through into the resident CALLPROC dispatch, and confirm P lands on FDINA = 106734.

Region bound: the FDINA worker is bounded strictly to the next FILSYS symbol WDIEN = 107106B (the MON 311B WriteDirEntry entry). The name index (the device description of the disk) is resolved from the directory table alongside the directory index; the exact word that maps to the manual's NAMIX is not isolated here beyond the B+1/B+2 result slots. Several link-cell targets (003752, 010500, 010506, 020274, 003776) sit below the 26000B segment load base; they are 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.