JV DOS

JV-DOS 2.0

JV-DOS runs as guest bytecode. It provides a shell, persistent named files, an editor, JVS interpretation, COM loading and small media viewers. Commands and filenames should be uppercase. Click the VM window before typing.

Startup uses a short banner and silent keyboard input. SOUND ON enables clicks. The prompt shows the drive and directory (0:\DOCS\>). HELP lists everyday commands; programming syntax lives in the JVS guide. CODEHELP and bank selection have been removed from the shell.

Programs can launch directly: enter HI.COM, DEMO.JVS, or a bare name such as HI. DOS first checks built-in commands, then searches the current folder for the exact filename, then a .COM suffix, then .JVS. Only executable/source file types launch this way; directories and media require their usual commands. Direct launches accept no arguments and do not extend the COM ABI. JVS source retains its existing restricted statement set.

Command help (HELP)	Directory (DIR)

Command	Purpose / example
HELP	Everyday shell commands
DRIVE, DRIVE N	Show the current device; selecting mounted N (0-255) resets to its volume root
INSTALL FILE.COM	Copy a binary program from the current folder to drive 0 root; preserve the source and refuse collisions
MV FILE.COM 0:	Move a binary program to drive 0 root; delete the source only after successful commit
DIR	List the current folder; folders show <DIR>
MKDIR NAME, MD NAME	Create a folder
CD NAME, CHDIR NAME	Enter a child folder
CD .., CD /, CD \	Go to the parent or volume root
RMDIR NAME, RD NAME	Remove an empty child folder
TYPE NAME, CAT NAME	Print file contents directly
VIEW NAME, MORE NAME	Read a document with navigation
WRITE NAME TEXT	Create or replace text
APPEND NAME TEXT	Append text to an existing file
EDIT NAME	Create/open a file in the editor
COPY OLD NEW	Copy to a new name
REN OLD NEW, RENAME OLD NEW	Rename a file to an unused name
MOVE NAME DEST	Move a file/folder into a sibling folder, or rename it to an unused name
MOVE NAME .., MOVE NAME /	Move a file/folder to its parent or volume root
DEL NAME, ERASE NAME, DELETE NAME	Delete a file
SAVE NAME HEX	Create binary content from uppercase hex byte pairs
JCTRL	Launch the bundled desktop on system disk 0
RUN NAME	Interpret text, load bytecode, or open image/music by type
IMAGE NAME, SHOW NAME	Display a palette image
PLAY NAME	Play a MIDI-note stream
BROWSE HOST/PATH	Basic HTTP text reader; optional port, e.g. BROWSE http://localhost:8000/index.html
PRINT TEXT, ECHO TEXT	Print literal text
CLS, CLEAR	Clear display
VER, MEM	Version and memory/file limits
SOUND ON, SOUND OFF	Enable/disable keyboard clicks
BEEP	Short tone
REBOOT	Restart the resident guest boot routine
EXIT	Halt the CPU

Each drive has one JVFS volume. Names use up to 12 uppercase letters, digits, dots, underscores or hyphens; names cannot begin with a dot. Directories grow across 1 KiB clusters and can contain more than 255 entries. Files have 24-bit lengths and share the full disk. TYPE/VIEW, COPY/APPEND and PLAY stream files rather than loading them entirely into RAM. COPY needs a new name; replacement writes and APPEND need enough temporary space for the replacement chain.

Commands accept a single name in the current folder. Navigate with CD rather than multi-component paths. CD . stays put; CD .. goes to the parent; CD / selects root. MOVE accepts a sibling folder, parent/root, or an unused new name, and rejects cycles and collisions. DEL rejects folders; RD removes empty folders. CLI and JVS source lines remain limited to 100 characters.

Editor and viewers

EDIT DEMO.JVS opens the guest source editor. Arrow keys move; Home/End navigate the line; Backspace and Delete remove characters; Enter inserts a newline; Tab indents. Esc saves and leaves. It is not a cancel operation. The editor highlights source text.

The document pager uses Down, Page Down or Space/Enter for the next page, Up/Page Up for the previous page, and Home for the beginning; Esc closes it. It retains the last 85 page starts. Image viewing closes with Esc, Enter or Q. Esc stops music and silences its voices. A running JVS program checks for Esc between statements.

Source editor	Document pager

Palette image	Music command during playback

The screenshot gallery also shows startup, desktop applications and program execution.

RUN dispatches image/music from their file type, interprets type-1 text, and otherwise validates and loads raw bytecode. It also heuristically treats binary content starting with printable bytes 32-90 as source. The supplied COM starts with opcode 2 to avoid that ambiguity. Filename extensions alone do not define the execution format.

See JVS programming, COM programming, and Tooling and Disk Workshop.

JCTRL launches the managed desktop from the root of system disk 0. Startup installs and updates an unchanged managed copy. Manual and modified copies are preserved. See the desktop guide.

Storage and RAM limits

JVFS replaces the old per-bank format. System revision 24 reformats old experimental test disks on startup; no migration is included. The CPU and storage instructions are unchanged. See the byte format and service ABI.

EDIT and fullscreen executable/source loading still use a bounded 61,200-byte RAM buffer. Inside JCTRL the DOS window and small graphics apps have an 8 KiB workspace; larger document COMs can use up to 91 pages. TextEdit has its own 4 KiB document limit. Oversized loads report an error. A failed editor save keeps the old disk file and retains the buffer for shortening and retrying. These RAM limits do not restrict streaming commands or file moves.

Shell history and completion

At the DOS prompt, Up recalls older commands and Down moves toward newer commands. The last 16 submitted, nonempty interactive lines are kept until reboot. Moving Down past the newest entry restores the line you were drafting, including its cursor position. Recalled commands can be edited and submitted again. JVS statements and editor text are not added to history.

Tab completes the word at the cursor. Repeated Tab cycles matching command names, or names in the current folder of the selected drive for file-command arguments (including both COPY/REN filenames). The rest of the input line is preserved. A completed final word receives a trailing space. Unmatched prefixes and replacements that exceed the 100-character line limit leave the line unchanged. Typing or moving the cursor starts a new completion search. In EDIT, Up/Down still navigate the document and Tab inserts four spaces.

Reading the kernel source

src/main/java/xyz/ignite4inferneo/jvdos/JvDosImage.java describes guest instructions with named OPCode values, one emitted instruction per line. Asm.emit checks operand counts before encoding bytes. Labels and the get/put, call/ret and file-buffer helpers hide address fixups and state layout.

A-D hold working values, E/F support existing addressing sequences, and G/H implement far branches and the COM entry stubs. I/J handle indirect RAM reads without overwriting A-H. K/L hold glyph pixel coordinates, avoiding temporary RAM writes during rendering. M supplies glyph ink and N-P carry far-service return addresses in the resident glyph/filesystem conventions. Helpers can overwrite their documented scratch registers; guest JVS variables A-P live separately at bank 0, page 252, offsets 224-239.

The kernel emits ordinary VCPU instructions. GuestFileSystem.java provides the shared driver; DosFileSystem.java and DesktopFileSystem.java are guest clients. Installation and Workshop implement the same disk format independently. The compact command dictionary, trimmed HELP and resident glyph renderer remain shared.

JCTRL desktop

Enter JCTRL to start the managed desktop. Startup also bundles TextEdit and Paint. For a manual copy, use Workshop Add JCTRL bundle, then RUN JCTRL.COM from its folder. The desktop guide covers mouse windows, the guest program runner, image/music playback, and installation.

Startup script

After DOS initializes, it runs AUTOEXEC.JVS from the volume root on system disk 0, if present. This also runs on REBOOT. Create it with EDIT AUTOEXEC.JVS while in the system root; Esc saves. It uses the normal JVS language and returns to the prompt when finished. Esc between statements stops it. Delete or rename the file to disable it.

For an automatic desktop launch, use WRITE AUTOEXEC.JVS JCTRL. JCTRL ends the current script and launches the bundled desktop; closing the desktop returns to DOS.

Basic HTTP reader

BROWSE is a fullscreen plain-HTTP text reader. It accepts a host/path or http://host[:port]/path, strips response headers and HTML tags, and retains up to 60,000 bytes in RAM. Up/Down scrolls, Home returns to the top, and Esc exits or cancels. HTTPS, redirects, JavaScript, CSS layout, entity decoding, clickable links and chunked responses are unsupported; the server must close the connection. Script/style contents can appear as text. For links, GET forms, redirects, chunked HTTP and the optional HTTPS gateway, use WEB.COM under JCTRL.