Repository navigation
Home
JavaVCPU is an experimental Java virtual CPU with 31 opcodes, sixteen byte-sized general-purpose registers, 128 KiB RAM, a 256 by 256 palette display, keyboard/mouse input, synthesized audio, persistent disks and asynchronous TCP networking. JV-DOS 2.0 is its resident guest operating system. JCTRL adds a desktop whose windows, program interpreter and applications also run as guest bytecode.
Start with Getting started, then enter HELP at the DOS prompt or JCTRL to open the desktop. Startup manages JCTRL.COM, TEXTEDIT.COM and PAINT.COM on drive 0. Disk Workshop imports host files and converts images and MIDI without a server.
| Guide | Contents |
|---|---|
| Screenshots | Current shell, editor, desktop, Paint, TextEdit, WEB and setup captures |
| Getting started | JDK 26, build/run, boot installation and project map |
| JavaVCPU architecture | Registers, memory banks, display, input, audio and storage |
| Instruction set | All 31 opcodes and operand conventions |
| JV-DOS 2.0 | Commands, folders/drives, history, editing, media and startup scripts |
| JCTRL desktop | Windows, Files, resident DOS, application execution and shared services |
| JCTRL applications | Paint, TextEdit, WEB and Pong controls and limits |
| Installers and setup | Managed apps, external media, INSTALL/MV and JCTRLSET.COM |
| Tooling and Disk Workshop | Disk editing, asset generation, checks and wiki publishing |
| JVS programming | Source syntax, arithmetic, loops and limits |
| COM programming | Guest bytecode, resident DOS and JCTRL application ABI v7 |
| Disk and media formats | JVFS 1, transactional replacements, JI images and JM music |
| Peripheral buses | Storage addressing, mounted devices and TCP registers |
| Example programs | Bare-metal and DOS programs |
These pages describe the current working tree as of October 22, 2026. JVFS replaces the old experimental per-bank filesystem; incompatible disks are reformatted on startup. Back up older images before using this version. Valid JVFS files survive firmware updates; unchanged managed desktop apps can be upgraded while modified/manual copies are preserved.
COM files contain JavaVCPU instructions. JVS is a small guest line interpreter. Legacy names such as JVCPM and DEMO_OS remain in firmware headers and source.
Source: JavaVCPU repository. Editable documentation lives in docs/wiki/; wiki/ is a Git submodule connected to the GitHub wiki repository. See the publishing workflow.