Virtual Filesystem

Virtual Filesystem

The simulated C: drive lives in prompt/javascript/fs.js as a JS object tree. Every directory and file the user can dir is defined there. It's editable: change the file, hard-refresh, the prompt sees the new tree.

Top-level layout

C:\
├── AUTOEXEC.BAT          runs on boot — calls `menu`
├── menu.bat              `cd systems\nmenu` (drops straight into the EMULATOR LAUNCHER)
└── SYSTEMS\              EMULATOR LAUNCHER: 1 HOMECOMP / 2 CONSOLE / 3 HANDHELD / 4 WIKI / 0 Exit
    ├── HOMECOMP\         ACORN (BBC / ELECTRON / MASTER) / AMSTRAD (CPC) /
    │                     APPLE (APPLE1 / APPLEII) / ATARI (400 / 800XL) /
    │                     COMMODRE (PET / VIC20 / MAX / C64 / C16 / PLUS4 / C128) /
    │                     MSX (MSX1 / MSX2) / SINCLAIR (SPECTRUM / ZX81) /
    │                     TANDY (TRS80 / COCO) / TI99
    ├── CONSOLE\          ATARI (2600 / 7800) / CVISION / INTV / NES /
    │                     ODYSSEY2 / VECTREX
    └── HANDHELD\         GAMEBOY (Game Boy / Color) / LYNX / GAMEGEAR

Which menus map to which emulators

All 32 bundled sub-systems run their games locally — every byte of game data is on the same origin.

Menu path	Backing emulator	Notes
CONSOLE → NES	EmulatorJS + FCEUmm	dir name is jsnes/ for legacy reasons
CONSOLE → ATARI → 2600	EmulatorJS + Stella
CONSOLE → ATARI → 7800	EmulatorJS + ProSystem	dir name is js7800/ for legacy reasons
CONSOLE → VECTREX	DrSnuggles/jsvecx	built-in Mine Storm as #11
CONSOLE → CVISION	EmulatorJS + gearcoleco	colecovision.rom BIOS bundled
CONSOLE → INTV	jzIntv WASM	exec.bin + grom.bin BIOS bundled
CONSOLE → ODYSSEY2	libretro-o2em → WASM + custom SDL2 frontend	o2rom.bin BIOS bundled
HANDHELD → GAMEBOY	EmulatorJS + gambatte (nightly)	Game Boy + Game Boy Color, one gbc/ menu
HANDHELD → LYNX	EmulatorJS + handy	lynxboot.img bundled
HANDHELD → GAMEGEAR	EmulatorJS + genesis_plus_gx
HOMECOMP → ACORN → BBC	jsbeeb
HOMECOMP → ACORN → ELECTRON	ElkJS	UEF snapshots
HOMECOMP → ACORN → MASTER	jsbeeb (?model=Master)	Elite uses DSD for drive 2
HOMECOMP → AMSTRAD → CPC	floooh tiny8bit CPC WASM	sokol_args URL params
HOMECOMP → APPLE → APPLE1	apple1js	tapes + Woz Monitor
HOMECOMP → APPLE → APPLEII	apple2js	.dsk images converted to JSON
HOMECOMP → ATARI → 400	atari800 (?machine=atari → OS-B / AltirraOS-800)
HOMECOMP → ATARI → 800XL	atari800 (default → AltirraOS-XL)	shares build with 400
HOMECOMP → COMMODRE → PET	Thomas Skibo's pet2001 (vanilla JS)	PET 2001 / BASIC 2 / 32 K
HOMECOMP → COMMODRE → VIC20	EmulatorJS + VICE xvic	memory_expansions='all'
HOMECOMP → COMMODRE → MAX	EmulatorJS + VICE x64 (Ultimax mode)	Japan-only 1982 console
HOMECOMP → COMMODRE → C64	EmulatorJS + VICE x64	real-time IEC loading
HOMECOMP → COMMODRE → C16	EmulatorJS + VICE xplus4 (C16 mode)
HOMECOMP → COMMODRE → PLUS4	EmulatorJS + VICE xplus4
HOMECOMP → COMMODRE → C128	EmulatorJS + VICE x128 (native mode)	per-game VICII/VDC switch
HOMECOMP → MSX → MSX1 / MSX2	WebMSX	shared core, ?M=MSX1 flag
HOMECOMP → SINCLAIR → SPECTRUM	JSSpeccy 3
HOMECOMP → SINCLAIR → ZX81	JtyOne
HOMECOMP → TANDY → TRS80	sdltrs (our own WASM build)	Model I; Level II BASIC ROM embedded
HOMECOMP → TANDY → COCO	XRoar	Tandy Color Computer
HOMECOMP → TI99	js99er (vanilla JS build)

Each system menu lists 10 games. Command-line machines add an 11th entry that boots a clean PROMPT / BASIC; the Vectrex lists built-in Mine Storm as #11. MSX has 10 + 10 (MSX1 + MSX2 sub-menus).

For the integration stories per emulator, see Emulators.

The per-system menu pattern

A typical <SYSTEM>\GAMES\ directory looks like:

GAMES\
├── menu.bat              numbered title list (45-char wide box-drawn menu)
├── 0.bat                 cd .. / cd .. / menu (back two levels)
├── 1.bat .. N.bat        each runs a named .bat
└── <key>.bat             one per title, with link: → emulator URL

How a user gets from the prompt to a game (NES example):

1   → cd systems / menu        (EMULATOR LAUNCHER → CONSOLE / HOMECOMP)
2   → cd console / menu          (CONSOLE SYSTEMS)
2   → cd nes / menu              (NES GAMES — auto-cd into games)
3   → contra                     (opens systems/jsnes/play.html?game=contra)
0   → cd .. / cd .. / menu       (back to CONSOLE menu)

The file-object schema

A node in fs.js is { name, directories?, files? } for directories, or one of these for files:

Field on a file	Meaning
data: '<batch>'	Treats the "file" as a batch script — each \n-separated line is dispatched as a command
link: '<url>'	Treats the file as a launcher — window.open(link, "_blank")
hidden: true	Hidden from dir output (still navigable via cd)

Game .bat files use link:. menu.bat and numbered launchers use data:.

The no-.html-files rule

The virtual filesystem only lists .bat files — game launchers, menu scripts, and the numbered shortcuts that route between them. Auxiliary HTML pages (each emulator's controls.html, future bezels, etc.) live on disk under systems/<name>/ but are reached from inside the emulator's entry HTML via a corner link, not from the DOS prompt.

This is period-correct: a DOS user typing dir shouldn't see .html.

See Customising the Filesystem for worked examples of adding entries.