HDD Image Findings — Working Research Notes (TEMPORARY)¶

Status: TEMPORARY WORKING NOTES — not final documentation. Aggregated from automated analysis of a local collection of ND HDD disk images using ndtool (the NDFS disk-image tool, read-only -i/-t/-x). Generated 2026-05-25. Purpose: a queryable knowledge base on MODE files, disk layout, BPUN/PROG homes, and RT/reentrant init, to feed the real install guides.

Provenance: "[obs]" = directly observed in extracted file contents. "[inf]/UNVERIFIED" = inference by the analyzing agent, not yet confirmed against a primary manual or source. Cross-check anything load-bearing before promoting it into a published guide.

1. Image inventory & validity¶

Image	Volume	Pages (tot/used)	Class	Notes
BIGDISK0-H.IMG	PACK-ONE	38400 / 5233	H, bare	minimal pack; only SYSTEM has files; no MODE files
BDH.IMG	PACK-ONE	38400 / 6741	H, bare	SINTRAN:DATA populated; mailbox welcome msg; no MODE files
BIGDISK0-K.IMG	PACK-ONE	38400 / 10334	K, skeleton	subsystem files are 0-byte stubs; no MODE
BIGDISK0-K2.IMG	PACK-UNO	38400 / 10334	K, skeleton	same as K, different volume name
BIGDISK0-SCSI.IMG	PACK-ONE	38400 / 10793	K, base	only `XMSG-STARTEX:MODE` (example); XMSG + FILE-MANAGER installed
scsi-k.img	PACK-ONE	64656 / 37477	K, production	full NOTIS/COSMOS office system; SCSI boot; rich MODE files
c3-k-bd.img	PACK-ONE	38400 / 16936	K, Compact C3	dev + process-control; TCP/IP; compilers; `-C3` MODE files
c3-k-bd-files.img	PACK-ONE	38400 / 16974	K, Compact C3	MODE files byte-identical to c3-k-bd
c3-k-bd-clean.img	PACK-ONE	38400 / 10691	K, base	symbol/patch base, no MODE (pre-config starting point)
c3-k.img	—	—	INVALID	not a valid NDFS image
BIGDISK0-L.IMG	PACK-ONE	38400 / 14861	L, populated	XMSG L03, COSMOS E, NOTIS-WP, compilers; no LOAD/HENT-MODE but many COSMOS load modes
BIGDISK0-L-TEST.IMG	—	—	INVALID	header all zeros
WD-L.IMG	—	—	INVALID	not parseable as NDFS
WD0-L.img	—	—	INVALID	shares boot header w/ BIGDISK0-L but body not NDFS-parseable
WD0-M.IMG	PACK-ONE	38400 / 12862	M, live pack	XMSG, ND500-MONITOR, DMAC, config; init via `PATCHES:OUT`
BIGDISK0-M.IMG	PACK-TWO	38400 / 12273	M, tool/library pack	BPUN-FILES languages, PED editor; SYSTEM progs are stubs
WD0.img	—	—	INVALID	not parseable as NDFS
BIGDISK0.IMG / a.IMG / RAND.IMG	—	—	INVALID	not valid NDFS images
BIGDISK1.IMG	PACK-TWO	38400 / 9	not a system disk	only NEW-SYSTEM:PROG + TEST1:SYMB
WD.IMG	PACK-ONE	38400 / 8209	tooling	MAC/FMAC/NPL assembler disk; no MODE
HD0.IMG	PACK-ONE	38400 / 12862	ND-100/500 service	only stock XMSG-STARTEX; ND500-MONITOR present
1325.img	PACK-ONE	36864 / 21709	OTS/COSMOS app	related to c3 site; no top-level LOAD/HENT-MODE-C3
c3_2024_1/2/5/6/7.img	PACK-ONE/UNO/TWO	36864 / ~30020	Compact C3 production	one filesystem ("Compact C3, Sys 16505"); full OTS/SCOPS + ND-500

Foreign/non-ND images (Sun/SunOS/BSD/Mac/IDE) were excluded by design.

2. The cold-start spine — HENT-MODE structure [obs]¶

The richest examples are scsi-k.img (SUPERVISOR), c3-k-bd.img and c3_2024_* (HENT-MODE-C3:MODE, SYSTEM). The canonical cold-start sequence observed:

@INITIAL-COMMAND ENTER-DIRECTORY,,<disk-device> 0      ; e.g. DISC-SCSI-1, DISC-74MB-1
@NEXT-INITIAL-COMMAND CONNECT SYS-OUT-1 105 R
@NEXT-INITIAL-COMMAND CLOSE 105
@NEXT-INITIAL-COMMAND BATCH
@NEXT-INITIAL-COMMAND APPEND-BATCH 1 LOAD-MODE:MODE SYS-OUT-1   ; queue warm-start
@RTENTER
@INITIALIZE-BACKGROUND-PROGRAMS                          ; = the "INIT-BACKGROUND" step
@RT-LOADER
YES
READ-BINARY DMAC 7                                       ; DMAC driver → segment 7
YES
READ-BINARY COS-TADADM 36                                ; COSMOS TAD admin → segment 36 (when COSMOS)
YES
EXIT
@BATCH
@MODE (RT)DEFINE-SEGMENTS:MODE,,,                         ; define RT segment names
@SINTRAN-SERVICE / @DEFINE-RTCOMMON-SIZE 2,,Y Y / @EXIT
@MAIL / @INIT 10 / @RUN-MAIL / @EXIT
@BATCH
... subsystem load-mode calls (reentrant dumps, COSMOS/XMSG/TCP loaders) ...
@APPEND-BATCH 1 LOAD-MODE:MODE SYS-OUT-1                  ; hand off to warm-start

Key facts learned: - INITIAL-COMMAND / NEXT-INITIAL-COMMAND build the boot command chain; the last one typically does APPEND-BATCH 1 LOAD-MODE:MODE to run LOAD-MODE as a batch job. This confirms the automatic-boot mechanism for 08-AUTOMATIC-BOOT-INITIAL-COMMANDS.md. [obs] - ENTER-DIRECTORY,,<device> 0 is where the boot disk device is named — varies by hardware: DISC-SCSI-1 (SCSI), DISC-74MB-1 (74 MB Winchester). [obs] - RT/background bring-up order is fixed: RTENTER → INITIALIZE-BACKGROUND-PROGRAMS → RT-LOADER READ-BINARY DMAC 7 → MAIL init. [obs] - The M-version live pack (WD0-M) uses a different mechanism: a (SYSTEM)PATCHES:OUT script does DEFINE-SEGMENT-FILE + RT-LOADER READ-BINARY DMAC 7 + DMAC S3PATCH + READ-BINARY ND500-MONITOR 62, rather than a HENT-MODE file. [obs]

3. The warm-start — LOAD-MODE structure [obs]¶

From scsi-k.img and c3* (LOAD-MODE:MODE / LOAD-MODE-C3:MODE):

@ENTER SYSTEM,<pwd>,,99
@SINTRAN-SERVICE / @CHANGE-DATAFIELD ... (terminal/printer types) / @EXIT
@SET-TERMINAL-TYPE 36..51 -5067
@DEFINE-MASS-STORAGE-UNIT FLOPPY-DISC-1 0   (and STREAMER-1 / FL-DISC-1)
@BATCH
@MODE (UTILITY)XMSG-START...:MODE,,         ; start XMSG
@START-TADADM                               ; COSMOS TAD admin
@MODE (COSMOS-BASIC)COS-START...:MODE,,      ; start COSMOS
@START-SPOOLING COSMOS-SPOOLING
@MODE (COSMOS-BASIC)COS-DEF-PRI...:MODE,,    ; define spool printers
@MODE (TCP-IP)TCP-START:MODE,,,              ; start TCP/IP (later systems)
@GIVE-SPOOL-PAGES <n>
@SINTRAN-SERVICE / @DEF-HDLC 1362B..1365B Y 4 / @EXIT   ; HDLC links
@SET-AVAILABLE
@OPERATOR === SYSTEM IS AVAILABLE ===

Learned: warm-start = start subsystems already loaded by cold-start, configure terminals/printers/HDLC, give spool pages, then SET-AVAILABLE. The first command in a SYSTEM batch job must be ENTER SYSTEM (<password>).... [obs]

4. How MODE files reference other MODE files [obs]¶

The chaining idiom is @MODE (<user>)<file>:MODE,,, (trailing commas = default params), and @CC <file>:MODE to comment-out. Top-level files orchestrate a tree:

HENT-MODE (cold)                          LOAD-MODE (warm)
├── (RT)DEFINE-SEGMENTS:MODE              ├── (UTILITY)XMSG-START*:MODE
├── XON-XOFF-ENAB:MODE / SPEED:MODE       ├── (COSMOS-BASIC)COS-START*:MODE
├── (SYSTEM)BACKUP-LOAD*:MODE             │     └── COS-DEF-PRIN*:MODE (spool printers)
├── (COSMOS-BASIC)COS-HENT*:MODE          └── (TCP-IP)TCP-START:MODE
│     ├── COS-XFTRA*:MODE  (XFTRAD daemon)
│     ├── COS-COSP-VS*:MODE (COSPO spooling)
│     ├── COS-FAU-VS*:MODE  (remote file access)
│     ├── COS-FA-SERV*:MODE (FS server / TADADM)
│     └── COS-FSART*:MODE   (FSART admin)
├── FM-DUMP:MODE             (file manager reentrant)
├── (TCP-IP)TCP-IP-LO*:MODE  (load TCP/IP stack)
└── OTS-HENT-C3:MODE → LOAD-IDB-SEG:MODE  (process-control IDB segment)

On the big production disk (scsi-k.img), a master dispatcher LOAD-SUBSYS:MODE calls ~19 sub-loaders (BACKUP-LOAD, XMSG-LOAD, COSMOS-HENT, ENCOS-LOAD, UE-LOAD, OE-LOAD, SPRINT-LOAD, DS-LOAD, ID-LOAD, etc.), and DUMP-REENTRANT:MODE dumps editor/backup/SNA reentrant code. [obs]

5. Software subsystems seen, and what each needs [obs]¶

Subsystem	Started/loaded by	Binaries (typical home)
XMSG (messaging)	`XMSG-LOAD*:MODE` + `START-XMSG` (SINTRAN-SERVICE)	XMSG-KERNEL/XROUT `:BPUN`, XMSG-COMMAND `:PROG` (UTILITY); versions K and L03 seen
COSMOS (network/file-transfer/spool)	`COS-HENT` (cold) + `COS-START` (warm); needs XMSG+TADADM first	COS-* `:PROG/:BPUN` (UTILITY / COSMOS-BASIC); COS-TADADM `:BPUN` (SYSTEM)
TCP/IP (COSMOS TCP gateway, ~1992)	`TCP-IP-LO*` (load) + `TCP-START`	TCPP/FTPRT, TELNET/FTP/RSH clients (TCP-IP user)
MAIL	`@MAIL / @INIT 10 / @RUN-MAIL` in HENT-MODE	—
RT-LOADER	core; used by every load mode	—
SINTRAN-SERVICE-PROG	config (RTCOMMON, HDLC, datafields, segment write-protect)	—
Spooling	`START-SPOOLING`, `GIVE-SPOOL-PAGES`	SSY-SPOOL (ND-SPOOL-AREA on big systems)
BACKUP-SYSTEM	`BACKUP-LOAD*:MODE` → DMA server to DMASEG	BACKUP-SERV/SYS `:BPUN/:PROG` (UTILITY)
NOTIS (WP/DS/ID/NCALC/DRAW/IR)	DS-LOAD/ID-LOAD/WP-DUMP modes	NOTIS user
User/Operator Environment (UE/OE)	UE-LOAD/OE-LOAD modes	USER-ENVIRONMENT / ND-OPERATIONS users
ENCOS	`ENCOS-LOAD*:MODE`	ENCOS servers (UTILITY)
ND-500	`RT-LOADER READ-BINARY ND500-MONITOR 62`	ND500-MONITOR `:BPUN` (SYSTEM), N500-SYMBOLS
Compilers/editors (FORTRAN, PLANC, PED, MAC, FMAC, NPL, QED, BRF, GPM, CC)	`DUMP-REENTRANT:MODE` / `DUMP-PROGRAM-REENTRANT`	`:BPUN` in BPUN-FILES; `:PROG` in SYSTEM
Process control / OTS-SCOPS (Compact C3)	`OTS-HENT*`/`LOAD-OTS`/`LOAD-IDB-SEG`	PICDISP/TREND/MELD/STATUP/PROBAS (OTS-* and RT users)

6. BPUN vs PROG file "home" convention [obs]¶

Strong, consistent pattern across disks:

File type	Home user/directory	Examples
Bootstrap `:BPUN`	(SYSTEM)	DMAC-191x, COS-TADADM, ND500-MONITOR
Subsystem `:BPUN` (loaded reentrant)	(UTILITY)	XMSG-KERNEL/XROUT, COSMOS, ENCOS, TCP servers, BACKUP
Language/tool `:BPUN` library	(BPUN-FILES)	FMAC, MAC, QED, NPL, DITAP, PED, FTN, ASSEMBLER-500, DEBUGGER
Floppy/util `:BPUN`	(FLOPPY-USER)	FLOPPY-MON, COP-VERIFY, FILSYS-INV, MCOPY
Ready-to-run `:PROG` (system tools/compilers)	(SYSTEM)	FMAC-1920C, S3-CONFIGURATION, compilers, PED
Feature `:PROG`	feature-specific user	XMSG (UTILITY), COSMOS (COSMOS-BASIC), TCP (TCP-IP), NOTIS (NOTIS), UE (USER-ENVIRONMENT)

The standard empty user set on a fresh install (SYSTEM, FLOPPY-USER, UTILITY, BPUN-FILES, SCRATCH, RT) is created in System initialisation.txt — see 03-FILESYSTEM-INIT.md. The "home" convention shows what each user directory is for. [obs]

7. Load-reentrant & RT subsystem init patterns [obs]¶

A. Driver/monitor load into a fixed segment (in HENT-MODE / PATCHES:OUT):

@RT-LOADER
YES
READ-BINARY DMAC 7              ; binary → segment number
YES
READ-BINARY ND500-MONITOR 62
YES
EXIT

B. Dump a reentrant program (editors, compilers, backup):

@DUMP-REENTRANT      <name> <lower> <upper> (<user>)<bpun-file>
@DUMP-PROGRAM-REENTRANT <name> (<user>)<prog-file> [<segname>]
@LOAD-REENTRANT-SEGMENT (<user>)<2nd-part-file> <segname>   ; for 2-segment progs (e.g. PLANC)
@DEFINE-REENTRANT-PROGRAM <name> <lower> <upper> <segname>  ; alias another reentrant prog

C. Full RT-server load pattern (COSMOS/TCP/NOTIS daemons):

@ABORT <prog> / @SCHEDULE 503
@RT-LOADER
CLEAR-SEGMENT <seg> / NEW-(BACKGROUND-)SEGMENT <seg>,<type>,... / SET-PAGE-TABLE <n>
READ-PROGFILE | READ-BINARY (<user>)<file>,<seg>,...
DECLARE-PROGRAM <prog>
CHANGE-RT-DESCRIPTION <prog> <prio> <seg> ...
WRITE-SEGMENT <seg>
END-LOAD | EXIT

D. RT segment-name definitions — (RT)DEFINE-SEGMENTS:MODE uses RT-LOADER DEF-SEG-NAME <name> <octal> [<owner>] to name system + application segments (S3IMAGE 2, S3COM 3, S3RTL 4, S3DMAC 7, S3XMSGP/D/R 33–35, S3TAD 36, IDB_0 250, etc.). [obs]

E. IDB in-memory database segment (process control):

@UNFIX IDB_0
@RT-LOADER / CLEAR-SEGMENT IDB_0 / SET-PAGE-TABLE 2
NEW-SEG IDB_0,2,... / ALLOCATE-AREA IDB_0,177777,0 / END / EXIT
@FIXC IDB_0 600          ; fix segment in memory at page 600

Not observed as literal commands in any MODE file: CHA-BACK-SEG-SI and a standalone DEFINE-SEGMENT-FILE inside HENT/LOAD-MODE (the latter appears in M's PATCHES:OUT and in System initialisation.txt). Background-segment sizing (CHA-BACK-SEG-SI) was only seen in the earlier SINTRAN-M archive Admin/HENT-MODE.txt, not in these disk images. UNVERIFIED whether it is version-specific.

8. Open questions / to validate before publishing¶

[ ] CHA-BACK-SEG-SI usage and when it's needed (seen in SINTRAN-M archive HENT-MODE.txt, not in images).
[ ] Exact semantics of READ-BINARY <name> <seg> segment numbering vs DEF-SEG-NAME.
[ ] Difference between DUMP-REENTRANT, DUMP-PROGRAM-REENTRANT, LOAD-REENTRANT-SEGMENT, DEFINE-REENTRANT-PROGRAM — validate against System Supervisor / RT-Loader manuals.
[ ] Why bare/skeleton packs (H, K) have 0-byte stub files — fresh-install placeholder? (UNVERIFIED)
[ ] SINTRAN version of WD.IMG / HD0.IMG / 1325.img (no version banner observed).
[ ] Confirm the boot device tokens (DISC-SCSI-1, DISC-74MB-1) against the CREATE-DIRECTORY device list in 01-DISK-DEVICES.md.

9. Source agents¶

Five parallel agents analyzed image groups H / K / L / M / generic. All used read-only ndtool ops and removed their temp extraction dirs. Raw per-image detail is summarized above; re-run a targeted ndtool -x on a specific image to recover any file's full contents.