Open tools/disk-workshop/index.html from a local checkout in a modern browser. Keep disk.js and desktop.js beside it. GitHub displays the HTML source rather than running the tool. No server or upload is needed; the original disk is never overwritten directly.
- Start the updated VM once to create/format JVFS, then stop it. Back up older images first: incompatible experimental formats are reformatted on startup.
- Use Open storage.img for a complete 16 MiB disk. Click folder rows to enter; Parent folder returns.
- Import files, create text/folders, or edit the selected file's Name, Format and Contents.
- Click Apply to disk to commit editor changes to the browser's working copy.
- Download updated disk saves
storage-updated.img. Replace the intended disk file with that download while the VM is stopped, then restart.
Download file exports the selected file's last applied bytes. Downloads omit pending editor edits. Reloading/closing loses changes not downloaded.
Names allow twelve uppercase JVFS characters; imported names normalize to an eight-character base and three-character extension. Ordinary imports replace same-name files in the current folder. Multi-file imports stage a whole clone, so a failed batch leaves the working disk intact.
Text imports (.txt/.jvs/.bat/.asm/.md) decode UTF-8, require ASCII, normalize CRLF/CR to LF, and expand tabs to four spaces. Other files use hex in the editor. COM import preserves raw bytes; it does not assemble source or validate instructions. Build commented hex listings before importing their generated COM files.
PNG/JPEG/GIF/WebP/BMP imports become JI images up to 240x240 with aspect ratio preserved. Alpha composites against black. Native .img files with JI headers are recognized as images. Paint's .jvi extension currently defaults to binary: select the imported file, set Format to Palette image, then Apply to disk.
MIDI format 0/1, at most 64 tracks, and PPQN timing become eight-voice JM events. Tempo changes and running status are supported; SMPTE timing is not. Pitched channels use triangle waves, percussion uses noise, and a ninth overlapping note steals the oldest voice. Instruments and velocity dynamics are not reproduced.
The composer accepts MIDI_NOTE FRAME_DURATION: note 0-127 and duration 1-255 roughly 33 ms frames. Compositions automatically use JM v2 when more than 255 events are required. Compositions can exceed 64 KiB; disk space and browser memory determine the practical size.
JVFS provides one volume per disk, 1 KiB clusters, 24-bit file lengths and growing directories. Firmware bytes are preserved and whole-volume ownership is validated. Replacement files need temporary space for the complete new chain. The file capacity differs from execution RAM:
| Consumer | Limit |
|---|---|
| Fullscreen DOS EDIT / COM / JVS loading | 61,200 bytes |
| JCTRL DOS window / small graphics app workspace | 8,192 bytes |
| Larger document COM workspace | 91 pages / 23,296 bytes |
| TextEdit document | 4,096 bytes |
| Streaming files/music and Workshop editing | Available disk space |
Add sample files creates/replaces WELCOME.TXT, SMILE.IMG and THEME.JMT. Add JCTRL bundle installs JCTRL.COM, TEXTEDIT.COM and PAINT.COM together. Identical copies are accepted; a different existing file, directory conflict or full disk rejects the whole bundle without partial changes. Startup manages these three apps in drive 0's root; Workshop copies are manual.
Import examples/jctrl/JCTRLSET.COM to prepare guest installation media. Build it with gradlew.bat desktopInstaller; it is a self-contained fullscreen DOS setup wizard. See installers.
Workshop has file renaming through Name + Apply and folder creation/navigation, but no folder move/rename or drag-and-drop interface. DOS/JCTRL provides those operations.
Open test.html beside the tool to run browser checks for large files/directories, moves, cycles, transaction failures, image/MIDI conversion and bundle installation. The same runDiskTests() function can run in a JavaScript engine with typed arrays and atob, without a browser DOM.
See the full guide and troubleshooting and disk/media formats.