SETBLK

MON 60 subfunction SETBLK = 141B (octal) = 0x61 = 97 decimal. NPL purpose (authoritative, 5P-P2-MON60.NPL, via SINTRAN/ND500/nd-500-mon/mon60-callers/SUBFUNCTION-TABLE.md): (set block size of a file) (dispatch 5NOPAR; no verbatim FUNCTION= prose). Operator command SET-BLOCK-SIZE (mon60-callers/INDEX.md sec 2.2).

All addresses are OCTAL ND-100 word addresses, BANK 1, base 0. Source: SINTRAN/ND500/nd-500-mon/nd-500-mon-j04.prog.asm

Handler location

Item	Value	Status
Enclosing ENTER-routine	002662 (framesize 000331) - the command interpreter	PROVEN
This command's case	005131 .. 005156	PROVEN
MON 60 call site	005154 JPL I 64 -> ptr 005240, bank1[005240]=146742 = thunk SAA 141	PROVEN
Error path	005155 (callsite+1) -> ptr 005017 = routine 002673 (interpreter error reporter)	PROVEN
Success path	005156 (callsite+2) -> ptr 005232 = 010613 (command loop)	PROVEN

Thunk verification (PROVEN, read from bytes)

146742 170541 SAA 141 ; 146743 125001 JMP I 1 ; 146744 146244 (gateway).

MON 60 subfunction used

Subfn	Octal / Hex / Dec	Thunk	Parameter-block layout	Skip/Error
SETBLK	141B / 0x61 / 97	146742	,X 6 = &local(B+105) = operand1; ,X 7 = &local(B+107) = operand2	err=005155->002673; ok=005156->010613

Slots 6 and 7 are stored (005135 STA ,X 6, 005153 STA ,X 7). Note the frame top B-176 is advanced +7 (005140) and restored -7 (005146) around the nested helper call at 005142.

What it does

1. Stores operand1 (already in D) into local B+105 and points param slot 1 at it. (005131-005135)
2. Evaluates operand2 via nested helper 005021 (selector SAA 1) and stores it into local B+107, pointing param slot 2 at it. (005136-005153)
3. Issues MON 60 SETBLK. (005154)
4. On error -> interpreter error reporter 002673; on success -> command loop 010613.

Unknown / inferred

• PROVEN: subfunction identity, thunk bytes, the two param stores, the frame- top adjust/restore, and the error/success targets.
• INFERRED: operand1/operand2 map to (file number, block size) in some order; the order was not traced. Helper 005021 is the command-line numeric-argument evaluator (same idiom as helper 002003 in LOAD-CONTROL-STORE). Handler 5NOPAR = generic forward path.