Visual assets in the MIT CADR and LM-3 software

Conclusion

The preserved CADR software contains substantially more visual material than its ordinary text fonts, but almost none of it looks like a modern image file on disk. The complete public System 46 tree contains no PNG, GIF, JPEG, PBM, or XBM files. Instead, its visual assets occur as Lisp Machine font objects, serialized Lisp arrays, XGP scan records, source-defined bit patterns, SUDS drawings and plot streams, and textual coordinate data.

Two standalone System 46 pictures can be decoded deterministically. 10LEAF reconstructs its stored array exactly; SCANIN CWH3 is normalized to the occupied black-pixel crop:

• 10LEAF is a 255 by 255, eight-bit grayscale photograph of leafy branches, serialized as a QFASL array;
• SCANIN CWH3 is a one-bit scan of page 3 of an unidentified mathematics text, used as input to the SCAN display demo and emitted as a translated crop.

Both recovered images remain local research outputs. Their occurrence in the released source tree does not by itself establish the authorship or redistribution rights of the photograph or scanned page. This repository therefore tracks the non-evaluating decoder and its evidence, not either reconstructed PNG.

The maintained LM-3 System 303 tree contains several graphical font atlases absent from the public System 46 snapshot, including abacus pieces, an animated beetle, worm marks, tally marks, pane diagrams, and the MIT mens et manus figures. Because the inspected Fossil check-in has no repository-level license file, this repository does not copy or publish decoded LM-3 glyph data.

Scope and classification

This audit compared two public source snapshots:

• the complete src/ tree of mietek/mit-cadr-system-software at commit 8e978d7d1704096a63edd4386a3b8326a2e584af, representing System 46;
• the LM-3 Fossil repository's System 303 check-in 4df393c68d7f083ce42d5c377039d26043cc18a9031ace28258dc97f4137eb91.

The search combined a complete filename and extension inventory with binary-aware string searches, inert QFASL decoding, contemporary file-format documentation, and inspection of executable consumers. A file is called an asset here when it stores a reusable picture, symbol, pattern, or drawing. A program such as MUNCH which creates new imagery at runtime is instead classified as a visual program.

Standalone System 46 pictures

Reconstructing the pictures locally

extract-cadr-visual-assets.py verifies the exact System 46 source revision's license and input hashes before it decodes either picture. It shares the bounded QFASL object parser used by the font recovery pipeline, recognizes only the exact CVPTS named-array conversion form, and never evaluates Lisp. Its XGP path parses only the reviewed SCANIN record envelope.

From a checkout whose argument is the public repository's src/ directory:

python3 scripts/extract-cadr-visual-assets.py \
  /path/to/mit-cadr-system-software/src \
  --output build/visual-assets/mit-cadr

python3 scripts/extract-cadr-visual-assets.py \
  /path/to/mit-cadr-system-software/src \
  --output build/visual-assets/mit-cadr \
  --check

When the pinned public source checkout is available, the optional integration test exercises license and artifact verification, both real decoders, PNG/catalog output, and the CLI check path:

MIT_CADR_SYSTEM46_SRC=/path/to/mit-cadr-system-software/src \
  python3 -m unittest -v \
  tests.test_visual_assets.PinnedSystem46IntegrationTests

The output directory contains 10leaf.png, scanin-cwh3.png, and a deterministic catalog.json. The entire directory is ignored by Git. Do not move these outputs into docs/assets/ unless their content rights are established separately.

Graphical fonts as sprite and symbol stores

The CADR font representation is also a convenient indexed bitmap container. Several “fonts” are better understood as small sprite atlases:

• MOUSE stores mouse arrows, rectangle corners, scrolling marks, and meter indicators;
• ARROW stores visible representations of format effectors as well as old window system blinkers;
• TOG stores switch-register state glyphs used by the display hacks;
• SHIP stores a torpedo, a sun, and two sets of 32 rotated ship sprites for Spacewar;
• BUG stores four 33-row beetle drawings in character positions A through D. A contemporary EINE bug report instructs the user to fill continuation lines with those characters as a redisplay stress case. It does not establish that the four glyphs were animated in System 46;
• SEARCH stores ten visibly labeled extended-search operators. Later maintained LM-3 source establishes their exact editor functions, from opening and closing a nesting level through “any character.”

The tracked font sheets and compiled-font sheets show these public System 46 artifacts. Their application evidence is maintained in the font usage audit, rather than inferred from appearance alone.

LM-3-only graphical fonts

The following compiled names are present in maintained System 303 and absent from the complete public System 46 tree. “Absent” is a snapshot comparison, not a claim that the LM-3 restoration created them or that they never existed in another earlier MIT software set.

A local row-major comparison found the four TVBGAR arrays bit-for-bit identical to the first 32 raster rows of System 46 BUG.KST glyphs A through D. That 733-byte public input has SHA-256 ad3ed4d542d5058d44d77dc2102410fbc6b1169403f75f1840e4e94fc68b52b8. TVBUG.QFASL uses the same motif but changes or adds internal markings. This cross-check establishes lineage between the public beetle source and the later animation data without assuming that every artifact is byte-identical.

PAINT fills, brushes, and window-system patterns

System 46 PAINT embeds nine repeating four-row paint patterns and eight sixteen-row brush masks in Lisp source. INIT-PAINTS tiles the paint patterns into 32 by 32 selectors and the brush masks into 16 by 16 selectors; the source also identifies the erasing paint, initial paint, and initial brush by list position. The individual shape names are TODO because the source supplies none. The values and selector roles are explicit in paint.7.

Two other source-defined display textures have exact UI roles:

• LABELS-HALFTONE is a 50 percent alternating checker tile NORed over old-window labels when HALFTONE-LABELS-FLAG is active;
• the font editor's GRAY-ARRAY is a generated 40 by 4 checker tile XORed over a selected grid point.

These are patterns, not hidden picture files. The separate color inks and raster patterns article explains the indexed color maps and named monochrome stipples in their display context.

SUDS drawings and plot streams

The System 46 tree contains a large hardware-design corpus:

The README records that one SUDS file for the Chaosnet board may have been lost from a damaged tape and later says that the surviving SUDS files appear to be CADR4 schematics. The DPLT reader explicitly describes .PLT as 36-bit files from SUDS and decodes vector, text, and diamond items for Dover output.

Eight particularly useful lmdoc drawings survive as CHOD1, CHODAM, CHODI, CHODTM, FIG1, FIG2, FIG3, and FIG5. Their labels and placement in the CADR documentation identify data paths, microinstruction fields, timing, memory/PDL/VMAP structure, and system or network topology. System 46 has companion .PLT exports for all of those names except FIG5; System 303 has the eight .DRW revisions but no companion .PLT files. These are structured technical drawings, not runtime screen assets.

Other bounded candidates

• lispm1/figs.texsq1 is a 9,179-byte ASCII file containing two named coordinate sets, LH24 and RH24, with 382 and 385 points. Its consumer and intended visual role remain TODO. SHA-256: 4906646490f0d6776b43e2723aeb096d6f6a36994bdbfcc6ff713fd2fd655d01.
• lmwind/flavor.pictur is a 726-byte spatial ASCII diagram of window flavor relationships, not a bitmap. SHA-256: 1f804bb67f631fc384c3ff0b7b6bec16092059f26b01db75ca4547002f1d999c.
• an archived Color-Ad source payload constructs a 10 by 10 diagonal color cursor at load time. It is a procedural archive fragment rather than stored raster data.
• the System 46 lmwind/ directory contains ten formatted .xgp document bodies: baswin, choice, frame, operat, sheet, stream, tscrol, typout, window, and winman, totaling 382,258 bytes. They preserve visual/document output and even supply font-use evidence, but they are not reusable runtime image assets;
• window/menu.press in System 303 is likewise a formatted Press document rather than a runtime screen image.

Procedural imagery is a separate category

Several visually important CADR programs contain no recoverable final picture:

• MUNCH generates its XOR pattern from arithmetic and an interactive switch register;
• LEXIPHAGE animates jaws erasing text rendered in 43VXMS;
• PICT survives in System 46 only as the 9,773-byte compiled artifact lmdemo/pict.qfasl, SHA-256 441432ea110f2e14a646053f62611976a79c55e30647278feb43d6a013527dbc. Non-evaluating symbol and string inspection exposes RANDOM-POINT-VECTOR, DRAW-LINE, CIRCLE, HYPERBOLA, CYCLE, POLY-CYCLE, and WARP; that is enough to classify it as procedural, but not to claim recovery of its original source;
• the GEB/GODEL/ESCHER/KUPFER material, QIX, Spacewar, and many display hacks similarly generate frames from code and state.

Preserving these requires source, runtime behavior, and interaction semantics rather than merely exporting an image. A screenshot can illustrate one run, but it is not a substitute for the program.

Open questions

• Identify the book, edition, and rights status of the SCANIN CWH3 page.
• Establish the photographer and publication rights of 10LEAF.
• Find a consumer or documentation for figs.texsq1 and determine what its two coordinate fields represent.
• Decode the SUDS .DRW editor format and the .PATXY, .RAY, and .AUGAT manufacturing formats without treating all of them as image formats by default.
• Find an executable consumer for the LM-3 PANES font and establish whether the full ICONS atlas had a standard system role.
• Locate authoritative license or provenance metadata for the maintained LM-3 Fossil corpus before tracking derived glyph sheets from its LM-3-only artifacts.

Last verified: 2026-07-17.