vc-linux

Preserving DOS software as source, not as an emulator image.

Most DOS software survives as a binary inside an emulator, and lives only as long as that emulator is maintained. vc-linux preserves programs a different way. Each one is kept as three things:

1. The original source, unedited. Volkov Commander's own assembly is in asm/ and asm405/. The other programs are in third_party/, each with its licence and the upstream commit it came from.
2. A reproducible build of that source, assembled or compiled the way it was originally.
3. A machine translation to C, made instruction by instruction and checked against a reference CPU (unicorn) from random states. The translated C is never edited by hand.

Only DOS and the PC hardware around the CPU are rewritten, by hand, in runtime/. The result is ordinary C that any C compiler can build. Today it runs as a native Linux program on your real files, and as WebAssembly in any browser. No emulator runs at run time.

Preserved so far	Author, year	Licence
Volkov Commander 4.99.09, the file manager	Vsevolod Volkov, 1991-2000	BSD-2 (released 2026)
Volkov Commander 4.05 and VCSETUP	Vsevolod Volkov, 1991-2000	BSD-2 (released 2026)
GW-BASIC	Microsoft, 1983	MIT (released 2020)
BASIC Computer Games, twelve of them	David H. Ahl, 1978	public domain (2022)
bootLogo, a Logo with turtle graphics	Oscar Toledo G., 2024	BSD-2
Rogue 5.4.4, the original roguelike	Michael Toy, Ken Arnold, Glenn Wichman, 1980-1985	BSD-3
Hack 1.0.3, between Rogue and NetHack	Jay Fenlason, Andries Brouwer, 1982-1985; maintained by NetBSD	BSD-3
VZ Editor 1.6	c.mos, Village Center, 1990s	BSD-3
MS-DOS Kermit 3.15	Columbia University, 1982-1997	BSD-3 (released 2011)
MS-DOS 2.0 COMMAND.COM, EDLIN, DEBUG, FIND, MORE, SORT and FC	Microsoft, 1983	MIT

Try it in your browser: notanemulator.com. VC starts at once, and runs MS-DOS's shell and utilities, VZ Editor, GW-BASIC, twelve classic BASIC games, bootLogo turtle graphics, Rogue and Hack from its H: drive, the way DOS did. It is the same translated code, compiled to WebAssembly.

How this differs from emulation and rewrites

	Keeps the original program	Runs without an emulator	Works on your real files
DOSBox, dosemu2, js-dos archives	yes	no	no: a fake drive, 8.3 names
Midnight Commander, far2l	no: different programs	yes	yes
vc-linux	yes: translated instruction by instruction	yes	yes, long and Cyrillic names

Quick start

curl -fLo vc https://github.com/evoleinik/vc-linux/releases/latest/download/vc-linux-x86_64
chmod +x vc && ./vc

That is one static binary for x86-64 Linux, with no dependencies. You need a terminal of at least 80×25. Set COLORTERM=truecolor for the exact VGA palette.

To build from source, you need gcc, make, uv, and an OpenWatcom 2.0 installation for the bundled 16-bit DOS C programs. Set WATCOM to that installation's root, or fetch the pinned version below (the 524 MB toolchain is not in this repository):

git clone https://github.com/evoleinik/vc-linux && cd vc-linux
tools/fetch-openwatcom.sh build/openwatcom && export WATCOM=$PWD/build/openwatcom
uv sync && make
build/vc

make rogue builds build/rogue/ROGUE.EXE and its verbose link map. Project-owned DOS shims adapt Rogue's Unix interfaces and 32-bit integer assumptions; the vendored Rogue and PDCurses sources are never edited.

make hack builds Hack 1.0.3 as build/hack/HACK.EXE with the same pinned OpenWatcom and compiled-C translation path. Its unedited NetBSD source is in third_party/hack; runtime/hack_dos supplies the DOS-specific startup, terminal and file handling in place of the Unix modules. IBM PC wall glyphs are drawn through the BIOS. The build supplies its data files beside the EXE.

build/vc [DIRECTORY] opens in that directory. Settings live in ~/.config/vc-linux/ and a log goes to ~/.cache/vc-linux/vc.log.

What works

Key	Action	Notes
F3	View	VC's own viewer
F4	Edit	opens $EDITOR on Linux; VZ Editor when unset/empty, and in the browser
F5, F6	Copy, rename or move	long and Cyrillic names kept
F7, F8	Make directory, delete	F8 on a symlink removes only the link
Alt-F10, Ctrl-Z	Directory tree	scans the whole drive, so use it on H:
Ctrl-Q, Ctrl-L	Quick view, info panel
Ins, Grey + − *	Select files	grey keys need application keypad mode, which vc turns on
Ctrl-[, Ctrl-]	Put the left or right panel's path on the command line	Ctrl-[ needs a terminal that reports keys
Ctrl-I, Ctrl-M	Put the selected names on the command line, then select them again	need a terminal that reports keys
Ctrl-H	Show or hide dotfiles	dotfiles carry the DOS hidden attribute
Ctrl-\	Go to the root of the drive
Alt-letter	Speed search	takes a * wildcard
Command line	Translated DOS programs; /bin/sh on Linux, COMMAND.COM in the browser	Searches the current DOS directory and DOS PATH for .COM/.EXE; Linux keeps its host shell
dos2 (Linux), command (browser)	Microsoft's original MS-DOS 2.0 shell	DIR, TYPE, COPY, ECHO and .BAT files; EXIT restores VC's panels
vc405 (Linux), Enter on H:\VC405\VC.COM (browser/door)	Volkov Commander 4.05 inside 4.99.09	F3 views a file; F10 returns to the newer VC
Enter on .BAS	GW-BASIC	SYSTEM returns to VC; Ctrl-Pause or Ctrl-Shift-B stops BASIC
kermit take bbs.tak, stay (Linux), or Enter on H:\BBS.TAK (browser)	Dial the BBS in MS-DOS Kermit	Ctrl-] then C returns to Kermit's prompt; HANGUP, then EXIT, returns to VC
bootlogo, or Enter on BOOTLOGO.COM	bootLogo turtle graphics	QUIT, then VC's Enter confirmation returns to the panels
rogue, or Enter on ROGUE.EXE	Original Rogue 5.4.4	h j k l or arrows move, ? gives help, Q then y quits, S saves
hack103 (Linux), hack or Enter on HACK.EXE (browser/door)	Hack 1.0.3	h j k l move, ? gives help, Q then y quits, S saves
Mouse	Click to move the cursor	SGR mouse reporting

Drives: C: is / and H: is your home directory. Names are shown in code page 866, so Cyrillic displays correctly.

Type dos2 on Linux, or command in the browser, for Microsoft's MS-DOS 2.0 prompt, then dir, echo hello, type FILE.TXT, or copy FILE.TXT COPY.TXT. exit returns to VC. The original EDLIN line editor, DEBUG, FIND, MORE, SORT and FC accompany it: for example, find "x" FILE.TXT, sort < FILE.TXT, and fc FILE.TXT COPY.TXT at its prompt. debug opens the - prompt; q quits. DEBUG can inspect files and memory, but newly assembled or modified code has no translation to execute.

In the browser VC's ordinary command line also uses H:\COMMAND.COM, including batch files. Utilities and DOS.TXT, a guide with three examples, live in H:\DOS on DOS PATH. On Linux, dos2 is the explicit DOS shell: ordinary VC commands still use /bin/sh, and Linux COMSPEC is unchanged. The seven DOS programs install in $XDG_CONFIG_HOME/vc-linux/DOS2 (default ~/.config/vc-linux/DOS2). Only COMMAND's own environment adds that directory to PATH: VC's find, sort, more, fc and command -v git retain their host-shell meanings. A byte-identical DOS2.COM alias sits beside the other installed programs, DOS.TXT and DOSLIC.TXT in the config directory. Exact unchanged copies from the old flat installation are retired; edited files and user-created symlinks stay untouched. No extra files are put directly in your home directory. Batch files on Linux run inside dos2. make msdos2 builds the unedited vendored source with JWasm and JWlink. third_party/msdos2/UPSTREAM records the Microsoft repository commit and MIT licence; the build's per-program comparison report third_party/msdos2/IDENTITY.md records where the sources postdate or differ from Microsoft's shipped binaries.

Type vc405 on Linux to open Volkov Commander 4.05 inside the newer VC. Its unedited COM installs as VC405.COM in the config directory; no other command name changes meaning. In the browser and BBS doors, open H:\VC405\VC.COM. F3 uses 4.05's own viewer, and F10 returns to 4.99.09. Its companion setup program lives in VC405/VCSETUP.COM. Both older programs receive their own VC= directory ($XDG_CONFIG_HOME/vc-linux/VC405 on Linux, H:\VC405 in the browser and doors), so their VC.INI cannot replace 4.99.09's settings. Renamed byte-identical copies still select the same translations. make vc405 builds both from the unedited asm405/ sources with an isolated JWasm TASM-compatibility mode; provenance and build comparison are in asm405/UPSTREAM.

Type gwbasic to run the original 1983 interpreter, translated ahead of time just like VC. Try PRINT 2+2, then SYSTEM. The installed GWBASIC.EXE is a real DOS file: EXEC reads it and selects a translation by its complete bytes, not its name. Renamed copies work. Direct DOS EXEC rejects changed or untranslated executables; typed commands fall back to the Linux shell. The shipped association's gwbasic command never falls back, so a BASIC file name cannot become shell syntax when the interpreter is missing or changed. The installed 4.99.09 VC.COM and VC.OVL paths always use their built-in translations, independently of those files. Other paths, including 4.05's VC.COM, select their translations by complete bytes. Linux installs the interpreter in the config directory; bring your own .bas files. Linux sound stays silent. A CALL or USR into code without a translation stops that BASIC session with a short message and returns to VC.

F4 opens the selected file in VZ Editor 1.6 (US), another translated DOS program. On Linux, a nonempty $EDITOR still takes precedence and receives the resolved host path as one argument. Otherwise VZ receives an absolute DOS short name, pinned to the selected pathname until the editor exits even if neighboring names change or another program replaces the file. VZ refuses file paths longer than its 63-byte absolute-path limit and current directories whose short path plus 13 bytes reaches 64; each VZ child gets a private short temporary directory for its swap files. Type vz NEW.TXT to create a file. Use the arrows to move, Alt-S (or Esc then S) to save, Enter to accept the name, and Alt-Q (or Esc then Q), then Y, to quit. F1 opens the English file menu; F12 shows help. The defaults write DOS CRLF lines and a final Ctrl-Z byte. The installed VZ.DEF enables backups (Eb+): saving keeps the previous contents in .BAK, including when a write fails partway. Restore that backup if a save fails. An unchanged earlier Eb- default is upgraded; customized definitions and symlinks are preserved, so check their Backup File option. make vz reproduces the shipped 55,856-byte VZUS.COM exactly without changing vendor sources. VZ.COM and its English .DEF files install beside GW-BASIC; EXEC still matches complete bytes.

Type bootlogo for Oscar Toledo G.'s original bootLogo. Try REPEAT 4 [REPEAT 4 [FD 20 RT 90] RT 90] or REPEAT 36 [FD 60 RT 170]. QUIT exits; VC's own DOS code then asks for Enter and restores its text panels. BOOTLOGO.COM is a real, 503-byte NASM-built COM file installed next to GW-BASIC. Renamed copies run by the same byte-matching EXEC rule. The logo command remains available for a host program such as UCBLogo.

Type rogue for the original dungeon game, compiled with OpenWatcom to a real large-model 8086 DOS EXE and then translated ahead of time. There is no native Rogue port running behind that command. y u b n move diagonally, i shows inventory, , picks up an item, and ? explains the other keys. S, then y, saves to rogue.sav; the next plain rogue restores it. Saves and rogue.scr scores live in the current DOS directory, not beside the installed executable. If automatic restore rejects a save, it is renamed to rogue.bad and a new game starts with a notice. An existing rogue.bad is never overwritten. The player name is fixed to Rogue, shell escape and Unix signals are disabled, and successful restore consumes the save, as in the original game.

Type hack103 on Linux for the BSD-licensed game that grew into NetHack. Its original experience and character-choice prompts remain; hack103 -C selects a Caveman directly. h j k l move, y u b n move diagonally, and ? opens help. S saves to HACK.SAV; the next plain hack103 restores it. Q, then y, quits back to VC (Space acknowledges any --More-- prompt). Unlike Rogue, Hack keeps data, help, hh, rumors, record, perm, saves and bones beside HACK.EXE: in $XDG_CONFIG_HOME/vc-linux/HACK on Linux (default ~/.config/vc-linux/HACK), never directly in your home or working directory. Scores, saves and bones are not reset on startup; saves and bones from another build are reported as out of date and deleted, as upstream did. The default player name is Hacker. Concurrent native VC processes lock separate playgrounds: the first uses HACK, and others use persistent PLAY0001 through PLAY0064 subdirectories with their own data, saves, levels, bones and scores. Each uses a read-write VCPLAY.LCK file with a kernel OFD lock, including on NFS homes. Secondary slots refresh their executable and static data under the lock when the installed files change; live games and scores are preserved. The same VC process keeps its playground when you save and relaunch. Locks are released when VC exits, including after a crash; saved files remain. To resume a secondary save later when the main playground is free, open that PLAYnnnn directory and type dos2 /c HACK.EXE. Existing directories and saves are not erased. Only the typed word hack103 launches the installed DOS game on Linux; its directory is not on native DOS PATH. Debian and Ubuntu's bsdgames installs /usr/games/hack, so hack must retain its /bin/sh meaning. Other typed names, including hack.exe, also keep their host meaning. Native Enter on an EXE uses this same shell-command path. An explicit launch from dos2 still matches complete DOS bytes, including renamed copies. Browser and door commands remain hack or Enter on H:\GAMES\HACK\HACK.EXE.

CGA modes 4/5 (320×200, four colours) and 6 (640×200, two colours) use real interlaced B800h video memory. GW-BASIC's SCREEN 1, PSET, LINE, CIRCLE and DRAW work; SCREEN 0 returns BASIC to text. Terminals display an 80×25 coloured braille reduction; a browser shows the exact pixels on a crisp canvas. The original BASIC has only 31 bytes of typeahead, so type long statements normally rather than pasting a whole line at once. bootLogo is deliberately tiny: always close brackets, keep procedure definitions under 120 characters, and avoid zero distances or repeat counts (which mean 65536).

In the browser, select H:\BBS.TAK and press Enter to dial the notanemulator BBS with the original MS-DOS Kermit 3.15. Its own script sets COM1 to 57600 baud and selects ANSI-BBS, Kermit's terminal mode with PC colours, transparent eight-bit characters and CP437. The association runs kermit stay, take BBS.TAK: Kermit's command-line STAY keeps its prompt open after you leave the terminal. The selected filename is passed as a pinned DOS short path, so commas cannot become Kermit commands. The virtual Hayes modem answers ATDT555-1992 with CONNECT 14400 and carries telnet data at about 14400 bits per second. Telnet negotiation is handled by the modem, not by a modified Kermit. The browser connects on dial to wss://axis.tail85247.ts.net:8443/; the page remains a static site.

Linux deliberately has no default TCP endpoint. Start it with VC_MODEM_555_1992=host:port build/vc to connect to a telnet BBS you can reach. Then type kermit take bbs.tak, stay on VC's command line, from any directory. Kermit's own TAKE searches the current directory and then DOS PATH; STAY keeps its prompt open after you leave the terminal. No init-file workaround or Kermit source change is needed. An unset endpoint, an unknown number, or an unavailable server produces NO ANSWER. BBS.TAK and KERMIT.TXT install beside KERMIT.EXE and the other files in $XDG_CONFIG_HOME/vc-linux (default ~/.config/vc-linux), on DOS PATH. Existing scripts and guides in that config directory are preserved. VC does not create, update, move or delete copies directly in your real home directory; any files left there by an earlier version remain untouched. make kermit rebuilds the pure-assembly executable with no_network defined on the assembler command line; vendor sources remain unedited. The source and licensing provenance, including both archive hashes, are in third_party/mskermit/UPSTREAM.

In Kermit's terminal, Ctrl-] followed by C returns to MS-Kermit> without hanging up. CONNECT resumes; HANGUP drops DTR; EXIT or QUIT returns to VC's panels. To use Hayes commands directly, leave a one-second typing gap, type +++, then wait another second for OK. Type ATH and Enter for NO CARRIER; ATO instead resumes the existing call. A disconnected server also produces NO CARRIER. KERMIT.TXT keeps these instructions beside the script: in the config directory on Linux, and at H:\KERMIT.TXT in the browser.

In a plain terminal, Ctrl-[ sends the same byte as Esc. Ctrl-I sends the same byte as Tab, and Ctrl-M the same as Enter. VC gives each of them a different job, so vc asks the terminal to report keys in full. kitty, foot, Ghostty, Alacritty and iTerm2 do it through the kitty keyboard protocol. WezTerm does too once enable_kitty_keyboard is on. xterm does it through modifyOtherKeys.

In your browser

The same translated C also compiles to WebAssembly with Emscripten. The page opens VC at once on a small in-memory H: drive holding a README, VC's history, its own assembly sources, VZ Editor, GW-BASIC, bootLogo, Rogue, Hack, Microsoft's DOS shell and utilities, and twelve of David Ahl's public-domain BASIC Computer Games. xterm.js shows the screen in the IBM VGA font. The page reports keys in full, so Ctrl-[, Ctrl-I and Ctrl-M work, and holding Shift, Ctrl or Alt swaps the key bar. Files vanish on reload. The command line runs Microsoft's COMMAND.COM, including dir, type, copy, echo and .BAT files. command opens its prompt and exit returns to VC. F4 edits with VZ. Open GAMES and press Enter on a .BAS file to play. BEEP, SOUND and PLAY use a Web Audio square wave after the first key press. Use Ctrl-Pause or Ctrl-Shift-B to stop a game, then SYSTEM to return to VC. BOOTLOGO.TXT explains bootLogo with a square, a star and the original README's flower. The original GAMES\SPIRAL.BAS example uses BASIC's SCREEN 1 and DRAW; press a key when it finishes to return to text. The CGA canvas occupies the same screen area as xterm and keeps its keyboard input active. H:\GAMES\ROGUE.EXE is also on the DOS PATH: type rogue from either panel directory, or press Enter on that EXE. Its saves, like all browser files, vanish on reload. Hack lives at H:\GAMES\HACK\HACK.EXE, also on DOS PATH. Its executable and data files are listed immediately and each loads on its first DOS open; its translated code loads on first execution. Enter starts it, and quitting returns to VC. Saves, bones and scores stay in that H: directory and vanish on reload. The BBS door files include a direct HACK door as well as Hack on the VC door's private H: drive.

The Source button, or Ctrl-Shift-F12, shows the original assembly behind the running code. It shows the line the CPU is on, with Volkov's comments and the lines around it. Below that are the callers that led there, found from real return addresses on the stack, and the last 32 lines that ran. It works for both VC versions, VCSETUP, GW-BASIC, bootLogo and VZ. For Rogue and Hack, compiled from C, it names the function. The sources load the first time the panel opens.

The page first downloads VC and its startup settings. H: immediately lists all files with their full names, sizes and dates; contents download on the first DOS open and stay cached for the session. Each translated program is still a separate wasm module, fetched the first time DOS runs it and kept for the session. On a phone held upright, a key pad appears under the screen with F1 to F10, arrows, Esc, Tab, Ins, Enter, sticky Ctrl, Alt and Shift, and a button that opens the phone's keyboard. The page text follows the browser's language in English, Russian or Ukrainian, and H:\ПРОЧТИ.TXT is the README in Russian.

The page counts visits with GoatCounter: no cookies and no personal data, and its count.js (ISC) is served from this site, so the only outside request is the count itself. Local builds on localhost are never counted.

To build it, put Emscripten on your PATH (source emsdk_env.sh), then:

make web          # build/web/: index.html, vc.mjs, vc.wasm and one wasm per program
make test-web     # Node checks VC, DOS shell/utilities, editors, games, Kermit, graphics and sound

Serve build/web/ over HTTPS, or HTTP on localhost, to open it. Lazy-file SHA-256 verification uses WebCrypto when available and a portable fallback otherwise. The design is in docs/plans/2026-10-01-browser-build.md.

Why shouldn't I use it?

• It is VC 4.99.09, an alpha from 2000. Its own editor is switched off in the source. Some menus point at DOS things that do not exist here, such as EMS memory and archivers.
• DOS limits stay. A command line holds 126 bytes, and vc refuses a longer one rather than run a truncated command. Characters with no code page 866 form, the characters DOS forbids in names (\ / : * ? " < > |) and trailing spaces or dots cannot be spelled in DOS. Those names show as name■~1A2B.txt, with a stable suffix that always reaches the right file.
• The screen is 80×25. It does not resize with your terminal.
• Ctrl-O shows VC's own screen. It does not show what your last shell command printed.
• Holding Shift, Ctrl or Alt changes the key bar only on terminals that speak the kitty keyboard protocol. Elsewhere, Ctrl-[, Ctrl-I and Ctrl-M act as Esc, Tab and Enter.
• Only Linux on x86-64 is tested.

How it works

flowchart LR
  ASM[VC.ASM, VCOVL.ASM] -->|JWasm| IMG[VC.COM, VC.OVL + listings]
  IMG -->|translator: listing + capstone| GEN[C, one function per procedure]
  GEN --> BIN[build/vc]
  RT[runtime: memory, dispatcher, MCBs, PSPs, EXEC] --> BIN
  FS[DOS file layer on Linux] --> BIN
  TERM[BIOS video, keyboard, mouse on a terminal] --> BIN

Loading

• The translator (translator/) reads JWasm or NASM instruction boundaries from the assembler listing and decodes the linked bytes with capstone. It emits C for each instruction, flags included. It also decodes bytes the CPU runs that the listing calls data. VC starts by executing the text RESIDENT. bootLogo's single mutable pen-colour operand is read from live memory. VZ's macro interrupt slot has two source-proved forms, selected and checked against live bytes. Four indirect DRAW entries are emitted in a separate, source-proved supplement; VC's and GW-BASIC's original generated C stay byte-identical. For compiled C, it reads the verbose Watcom link map, checks every linked object's initialized bytes and relocations (C library members included), and checks WDIS instruction boundaries against Capstone before emitting C. JWasm cannot preserve all Watcom instruction encodings when reassembling symbolic disassembly; the verified map-driven path avoids changing the DOS executable.
• The runtime (runtime/rt.c, runtime/dos_core.c) keeps the machine faithful: a 1 MB memory array, a real stack, a real interrupt vector table, MCB chain and PSPs. VC's tricks run as written. It runs VC.OVL as a child process, splits its own memory block, and copies its resident code elsewhere. The dispatcher finds that copied code by its bytes.
• The DOS file layer (runtime/dos_fs.c) maps INT 21h file calls, including the 71xxh long-name family, to Linux.
• The BIOS layer (runtime/bios.c, runtime/term.c) draws video memory to the terminal as ANSI output, and feeds terminal input into the BIOS keyboard buffer.

The full design and every decision are in docs/plans/2026-09-30-native-port.md.

Tests

make test

Suite	What it proves
test-translator	Every distinct instruction in both VCs, VCSETUP, GW-BASIC, bootLogo, Rogue, Hack, VZ, Kermit and MS-DOS matches Unicorn from 32 random states each. All 17 earlier generated C files stay byte-identical. One whole routine matches the original on all 131,072 inputs.
test-vc405-build	Unedited licensed 4.05 sources and reproducible VC.COM/VCSETUP.COM bytes identical to the TASM builds.
test-rogue-build	The original Rogue/PDCurses DOS build, linked runtime licence and reproducible EXE bytes.
test-hack-build	Unedited NetBSD Hack source, DOS shims and data files, a reproducible EXE and its pinned SHA-256.
test-vz-build	Exact shipped US COM bytes, reproducible map/listings, and the build-time MASM compatibility layer.
test-fs	The DOS file layer, DOS 1.x FCB calls, and per-process short-path leases: over 4,400 checks against a temporary tree.
test-exec	Byte-identical EXEC, DOS search order, command tails, safe F4/associations, VZ path/temp limits and child cleanup.
test-machine	Timer interrupts, IF, HLT, Ctrl-Break, PIT speaker frequencies and declared mutable operands.
test-kermit-build	Unedited, licensed Kermit sources, a reproducible pure-assembly EXE and complete linked listings.
test-msdos2-build	Unedited Microsoft sources, reproducible COMMAND.COM and six utilities, and per-program shipped-binary comparisons.
test-modem, test-serial-machine	UART registers, DLAB, real IRQ 4/8259 EOI, INT 14h, Hayes commands, guard timing, 14400-bps pacing and exact telnet replies to the captured BBS.
test-modem-transport	Real nonblocking TCP on loopback, including failure and disconnect behavior.
test-embed	Exact native/web DOS-file round trips, VC image deduplication, native-only lazy-asset exclusion, and bounded startup decompression with corruption checks.
test-process	Child fault recovery, parent interrupt/device state, and fatal no-translation faults in VC itself.
test-term	Key parsing, the screen renderer, and BIOS video, keyboard and mouse: about 5,600 checks.
test-cga	Every CGA mode and pixel address, palette, XOR/readback, graphics glyphs, cursor and scrolling: over 823,000 checks.
test-ini	The shipped VC.INI passes VC's own checksum and suits Linux.
test-web	The WebAssembly build under Node: VC, COMMAND.COM DIR/batch commands and all seven lazy DOS utilities, VZ F4/edit/save/quit with MEMFS readback, Rogue play/save/restore, lazy Hack startup/status, GW-BASIC, bootLogo, Kermit BBS dial/type/hangup/EXIT, exact CGA pixels, canvas transitions and sound. Needs Emscripten.
test-e2e	VC in a pseudo-terminal: file operations and keys, real DOS launches, identity/injection checks, VZ editing and backups, Rogue and Hack play/save/restore, Kermit's full BBS workflow, Ctrl-Break, every shipped BASIC game's first prompt, Logo drawings and BASIC graphics.

Every finding from the three code reviews was fixed with a test that failed on the old code first.

The Kermit e2e tests replay tests/fixtures/enigma-connect-2026-10-02.bin using a local TCP BBS and an injected binary WebSocket in Node; neither contacts the live server. Restricted environments that deny socket() cannot run the TCP gate. Supplemental native syscall and pipe-transport tests exercise the same modem and translated Kermit without network access, but do not count as the TCP gate.

The browser keeps the same 1.3 MB first-load limit, with a gate requiring at least 150 KB less than the previous 1,299,288 gzip bytes. Startup reconstructs the newer VC's files from its linked image bytes and keeps VC.INI, VC.EXT and VCEDIT.EXT inside main. Other contents use immutable hashed filenames and the same bounded asynchronous fetch as program modules. A failed fetch returns a DOS error without ending VC. EXEC compares complete file bytes against a private original reference, never mutable guest data or a filename guess. Native Linux and door files remain fully embedded and need no downloads.

Debugging

• VC_TRACE=1 build/vc logs every INT 21h call with its string argument and result.
• kill -USR1 <pid> logs the registers and the last 256 addresses the dispatcher ran.
• VC_SCREEN_DUMP=file writes video memory as text after every render. In CGA modes it writes the 80×25 braille drawing.
• VC_FRAME_DUMP=file writes exact pixels as a binary P5 PGM: 320×200 with maximum 3 (modes 4/5), or 640×200 with maximum 1 (mode 6). Bytes are raw CGA palette indices, not converted brightness. Returning to text leaves the last graphics frame available for inspection.

Layout

• asm/ VC 4.99.09 sources by Vsevolod V. Volkov, BSD-2, from the ddanila/vc build branch.
• asm405/ unedited VC 4.05 and VCSETUP sources, with their BSD-2 licence and pinned provenance.
• translator/ Python: JWasm/NASM listing plus linked image to C.
• runtime/ C: machine state, dispatcher, loader, DOS and BIOS services, terminal.
• data/ default VC.INI (written by VC itself), VCEDIT.EXT, VC.HLP.
• web/ the browser page, its H: README, and vendored xterm.js and IBM VGA font with their licences.
• tools/ JWasm, vcini.py (edit VC.INI safely), snapshot.py (screen to HTML), social_preview.py.
• tests/ all suites. tests/spike_puttime/ is the first proof that translation works.
• docs/ the plan and the work briefs that built this.

History

Vsevolod Volkov wrote VC as a student at Kyiv Polytechnic, where he studied electronics. It first appeared in the Softpanorama Bulletin, a monthly magazine on floppy disks, in December 1992. It came as a New Year gift to readers. A stable beta had circulated for about six months before that. In May 2026 Volkov told Danila Sukharev how it began:

Initially, the program was conceived simply as a joke: a tiny assembler program that looked like NC 3.0, whose only function was to list directory contents. Then, in my spare time, I added individual functions: copying, viewing, and so on. After a while, I had something usable. Moreover, on those PC/XT-class computers, the program ran significantly faster and took up less precious RAM. I began developing it for my own use. Other users noticed the program, and it began to spread around the world. Back then, it didn't have its own name. Users came up with the name Volkov Commander.

VC 4 fits in one COM file under 64 KB. It added keys that later file managers copied. Ctrl-[ and Ctrl-] put a panel's path on the command line. Ctrl-I puts the selected names there. Nikolai Bezroukov, who ran Softpanorama, tells the story in Volkov Commander: a masterpiece of assembler programming.

The preserved 4.05 main source is dated 16 June 2000, and its separate VCSETUP source 14 June. It builds one tiny-model VC.COM with its internal editor included. The 4.99.09 alpha sources are dated 16 July 2000: the main program is split between a resident VC.COM and a medium-model VC.OVL, its file layer handles long names, and the internal editor code is commented out. These are differences visible in the two source trees, not inferred release notes.

Citing and archives

Each release is archived on Zenodo. The DOI 10.5281/zenodo.23085585 always resolves to the latest release. CITATION.cff gives the full citation, and GitHub's "Cite this repository" button reads it. Software Heritage also keeps the full git history, at archive.softwareheritage.org.

Credits and license

Volkov Commander is by Vsevolod V. Volkov, who released the sources under the BSD 2-Clause license in 2026 (asm/LICENSE.TXT). Danila Sukharev preserved them and made them build with JWasm in ddanila/vc. JWasm is by Andreas Grech and others, under the Sybase Open Watcom Public License (tools/jwasm/README.md).

GW-BASIC is Microsoft's MIT-licensed 1983 source with the OEM work from TK Chia's fork (third_party/gwbasic). Its pinned version is in UPSTREAM. David Ahl placed his works in the public domain in 2022; the game listings are vendored from coding-horror/basic-computer-games. Build-time conversion changes DOS names and line endings; Star Trek additionally gets spaces around compact TO/STEP keywords for this interpreter's tokenizer. Vendored listings stay unchanged. The first-prompt gate is not a claim that every later branch of a game was tested.

bootLogo is Oscar Toledo G.'s BSD-2-CLAUSE Logo (third_party/bootlogo); NASM 3.02 builds its unchanged COM source (tools/nasm). Graphics text uses Daniel Hepper's public-domain 8×8 fonts (third_party/font8x8). The shared CP437/866 box and block characters have glyphs; other unsupported non-ASCII graphics characters remain blank. web/GAMES/SPIRAL.BAS is an original example under this repository's BSD-2 license, separate from Ahl's public-domain games.

Rogue 5.4.4 is by Michael Toy, Ken Arnold and Glenn Wichman, with Nicholas Kisseberth's portable save and platform code (BSD-3-Clause; third_party/rogue). PDCurses is public domain (third_party/pdcurses). OpenWatcom's linked C runtime uses the Sybase Open Watcom Public License. ROGUELIC.TXT, PDCLIC.TXT, and OWLIC.TXT accompany the installed game and its browser copy.

Hack 1.0.3 descends from Jay Fenlason's 1982 Hack and Andries Brouwer's 1985 release, maintained in NetBSD's games/hack. The unedited vendored snapshot is NetBSD commit f037b5fcaa6db302271bbb445039a3a513b2e28c (2026-08-14), with the CWI Amsterdam and Jay Fenlason BSD-3-Clause notices in third_party/hack. HACKLIC.TXT, FENLIC.TXT and OpenWatcom's OWLIC.TXT accompany every installed copy. DOS adaptations live separately under runtime/hack_dos.

VZ Editor 1.6 is by c.mos (Village Center), BSD-3-Clause (third_party/vzeditor/LICENSE). The pinned US executable is reproduced byte-for-byte, with its original English definitions installed alongside it except for the backup-enabled VZ.DEF default described above. The browser drive includes its licence as VZLIC.TXT.

MS-DOS 2.0's COMMAND.COM, EDLIN, DEBUG, FIND, MORE, SORT and FC are Microsoft source releases under the MIT licence (third_party/msdos2/LICENSE). Their source-built DOS files are translated independently and lazily loaded in the browser; H:\DOS\DOSLIC.TXT carries the licence there. A program-specific SETVER table reports DOS 2.0 to these seven images without changing other programs.

The translator, runtime and tests are BSD 2-Clause (LICENSE). They were built with Claude Code and OpenAI Codex.