07 — Disk Layout & What CREATE-DIRECTORY Does¶
Status: SCAFFOLD. No assumptions. Facts below are transcribed from the SINTRAN-K/L archives (
FILE-INFO/BIGDISK0-K.txt,BIGDISK0-L.TXT). Anything not present in source is left as an explicit TODO, not inferred.
On-disk directory structure (verified header fields)¶
A SINTRAN directory dump reports these header fields (verbatim from BIGDISK0-K.txt):
| Field | Value (PACK-ONE, 75 MB, K) | Source |
|---|---|---|
| Directory name | PACK-ONE |
BIGDISK0-K.txt |
| Filesystem image size | 38400 pages | BIGDISK0-K.txt |
| Object file index pointer | 18684 (SI: 0x1, indexed) | BIGDISK0-K.txt |
| User file index pointer | 18686 (SI: 0x1, indexed) | BIGDISK0-K.txt |
| Bit file pointer | 18468 (SI: 0x0, contiguous) | BIGDISK0-K.txt |
| No. of unreserved pages | 18438 | BIGDISK0-K.txt |
These four pointers (object-file index, user-file index, bit file, plus the unreserved page count) are the structures a directory must contain. TODO: confirm from an ND manual that CREATE-DIRECTORY is what initialises exactly these — currently only observed in the resulting dump, not yet tied to the command in a primary source.
CREATE-DIRECTORY command form (verified)¶
From System initialisation.txt:
CREATE-DIRECTORY PACK-ONE DISC-75MB-1 0
| Argument | Value | Meaning (TODO: confirm against command reference) |
|---|---|---|
| 1 | PACK-ONE |
directory (volume) name |
| 2 | DISC-75MB-1 |
device + unit |
| 3 | 0 |
subunit |
Diagrams (TODO — to be authored, following MERMAID_COLOR_STANDARDS.md)¶
- [ ] Disk layout after install (directory header → object/user/bit files → reserved files).
- [ ] Flowchart: what executing CREATE-DIRECTORY does, step by step.
Diagrams will be added only once each step is verified against a primary source (ND manual or source-code), per the no-assumptions rule. The dump above gives the result; the mechanism must be confirmed before being drawn.
TODO¶
- Page ↔ block relationship for the device.
- Whether CREATE-DIRECTORY formats or assumes a formatted/sized image (scope note in 01).
- Cross-link command to OPCOM / System Supervisor reference.