Links: The Challenge of Golf (Tandy VIS, 1992) — a documentation pass

A measured description of the Tandy Video Information System pressing of Links: The Challenge of Golf (Access Software, 1992): a 3.9 MB CD-ROM image whose thirteen files include nine archives in an undocumented container that nobody in this collection had ever opened.

No bytes of the product are published here. Hashes, formats, measurements and four new tools; no assets, no image, no executable.

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The short card

object	Links - The Challenge of Golf (USA).bin + .cue, MODE1/2352
raw image	3,939,600 B = 1,675 sectors × 2,352, exact
user data	3,430,400 B; declared 1,671 blocks, residue 4 of run-out
volume	LINKSVIS, publisher TANDY, preparer MERIDIAN_DATA_CD_PUBLISHER
mastered	1992-10-23 20:42:28; the program was linked at 16:46 the day before
filesystem	13 files, 0 directories, 2,284,337 file bytes, no Joliet
how full	0.5030 % of a 74-minute CD-ROM; 545 sectors are all zero
the container	MDmd — 9 files, 1,855,971 B, 81.2477 % of the file bytes
opened	327 nodes, 320 members, residue 0 on 9 of 9, expanding to 3,069,433 B
the codec	variable-width LZW, LSB-first, clear 256, ceiling 13 bits — 320 of 320 members decode to their declared length
the pictures	GIFM is a GIF whose image data is raw indices, because the archive above it already applies GIF's LZW
the sound	97 RIFF WAVE, 96 at 11,025 Hz, 89.134 s of a golf commentator; 19 stored uncompressed
the program	GOLF.EXE, 157,780 B, real-mode DOS MZ, ne.py and pe.py both refuse it
the bridge	GOLF.EXE names 263 of 318 member names — 82.7 % — verbatim or by template
against the MS-DOS release	197 of 197 shared archive members are byte-identical
thesis	43.2720 % of file bytes is recorded PCM; 41.0391 % distinct; 25.0908 % of the raw image
the game test	4 of 4 on the amendment proposed here; 3 of 4 on the original wording
protection	0 hits on 11 markers, over 15 files and again over 320 members
score	inherited 13.00 / 13.00; open 19.25 / 24.50

What this session found that was not known

• The container is a recursive node tree, not "an archive with a directory": a 122-byte header at every depth, and a tiling check whose two numbers come from two places and agree 320 times.
• The codec is LZW and the file extension had nothing to do with finding it. Nineteen members are stored uncompressed and every one is a RIFF header — a known-plaintext attack the format hands over for free.
• GIFM is a GIF with the compression hoisted one level up, into the archive, so a picture and a .WAV get the same treatment and a picture is never compressed twice.
• The two files dated 1990 and 1991 really are the MS-DOS original's, not by inference from a date but because they are byte-identical to it — as is every one of the 197 archive members the two releases share.
• The VIS port rebuilt the interface and replaced the sound entirely, and kept the course, the lie tables and the top view unchanged.
• One member of one archive was picked up from C:\WIN31\, and it is the Windows 3.1 chime — confirmed three independent ways.
• The disc's own interface asks the player to swap in another Course CD, on a platter with room for 866 more courses.
• TITLE.SCR is a 640 x 400 picture plus a separate 640 x 22 strip reading Press BUTTON (A) to Continue, and it carries (C) 1992 ACCESS SOFTWARE INC drawn into the artwork — the only year anywhere on the disc outside a date field. Its bytes are not palette indices: index 0 forms 45 pure blocks whose true colours run from orange through black to blue and magenta, and every byte in an even column has bit 7 clear, 128,000 of 128,000.
• Sector 1667 is the only sector in the image whose reserved field is non-zero and whose P and Q parity both fail, and it is still unexplained.

Chapters

00 — predictions	written before the disc was opened, 46 clauses, wrong ones left standing
01 — the object	what it is, four denominators, what it keeps and loses
02 — datasheet	every figure with the command that makes it again
03 — the medium	a chapter about emptiness, and one sector nobody can explain
04 — the container	MDmd: a tree of identical nodes, tiling with residue 0
05 — the codec	LZW, found by known plaintext, 320 of 320
06 — the pictures	GIFM is a GIF, and the colour table is ten bytes from where it looks
07 — the sound	89 seconds of a commentator, and one chime from C:\WIN31\
08 — the executable	a DOS program that names 82.7 % of the disc's members
09 — the game test	a criterion that only works on one binary format is a criterion about binary formats
10 — against the collection	zero at the file level, 197 of 197 one level down
11 — the thesis	the first VIS entry outside the nineties
12 — privacy	three corporate names, one first name in a filename, no user state
13 — leftovers	what is described and not explained
14 — corrections and the score	fourteen corrections, eight of them mine

Tools

Four written here, in tools/:

• mdmd.py — reader for the container. --validate before --census, --verify decodes every member against its declared length, and it refuses four negative controls that ship on the disc.
• mldpng.py — renders the GIFM pictures to PNG using only zlib.
• palscore.py — decides which reading of a palette is right, against controls. The method is vis-sherlockholmes-doc's and the citation is the point.
• predcount.py — counts prediction clauses and sums the two score columns by command, and fails loudly on a missing tag or a gap in the numbering.

414 more are inherited. toolscan.py reports 0 findings over 418 .py files plus every .md and .txt this session wrote, with all three positive controls firing.

Reproducing

python tools/iso9660.py "Links - The Challenge of Golf (USA).bin" --extract _work/iso
python tools/mdmd.py _work/iso/LINKS.CFG --validate          # must refuse
python tools/mdmd.py _work/iso/*.LZ _work/iso/TORREY_P.CRS --validate
python tools/mdmd.py _work/iso/*.LZ _work/iso/TORREY_P.CRS --verify
python tools/mdmd.py _work/iso/GRAPHICS.LZ --extract _work/members/GRAPHICS.LZ
python tools/mldpng.py --dir _work/members/GRAPHICS.LZ _work/png

The image, the cue sheet and everything derived from them stay in _work\ and are not published.

Related

• vis-platformnotes-doc — the platform checklist. This disc adds a sixth CONTROL.TAT row and makes fdiv at 0x0B0 3 of 3.
• vis-gamelist-doc — the index and the G1–G4 test. Chapter 09 proposes an amendment to it.
• vis-sherlockholmes-doc — the first VIS disc, and the source of the palette method used here.
• vis-racetheclock-doc — the second, and the source of the multi-denominator thesis figure.
• pc-linksthechallengeofgolf-doc — the MS-DOS release of the same title, used here as a measuring instrument and documented elsewhere.