.BAT File Format – Dialects and versions

Windows batch file

There is no standard for the batch language. Each interpreter defines it, and they agree on a core that goes back to the first versions of DOS. The dates below are the well-known ones; features given without a version are not tied to a release because that was not checked against a primary source.

What each interpreter knows

FeatureCOMMAND.COM (DOS)cmd.exe4DOS / Take Command
rem, echo, pause, goto, labelsyesyesyes
%0–%9, shiftyesyesyes, with %# and more
if (string, exist, errorlevel), for in doyesyesyes
set, %name%yesyesyes
call of another batch fileyesyesyes
call :label, goto :eof, exit /bnoyes (extensions)GOSUB / RETURN
& && || between commandsnoyesyes, with ^ as the separator in 4DOS
if /i, if defined, EQU … GEQnoyes (extensions)own IFF and expressions
for /d /r /l /fnoyes (extensions)own FOR and DO
set /a, set /p, setlocal, endlocalnoyesyes
%var:~n,m%, %~dp0, !var!noyesfunctions such as %@LEN[...]
Long file names, spaces in namesonly through lfnfor and quotes on Windows 9xyesyes
Unicode textnono (code page); cmd /u output onlyyes in the Windows versions

MS-DOS and COMMAND.COM

Batch files exist from DOS 1.0 (1981), when a .BAT file already took %0 to %9. Later versions of DOS added the environment and %name%, if, for, shift, errorlevel, redirection and pipes, call, the @ prefix, choice as an external program, and, in MS-DOS 6, start-up menus in CONFIG.SYS; which release added which was not checked here. COMMAND.COM is a 16-bit program with a very short command line limit (127 characters is the figure usually given) and eight-character file names. The same interpreter ran under Windows 95, 98 and Me, with long file names and start added, and under the NTVDM of Windows NT for 16-bit programs.

AUTOEXEC.BAT and CONFIG.SYS are the start-up files. Only AUTOEXEC.BAT is a batch file; CONFIG.SYS has its own syntax.

Windows NT and cmd.exe

Windows NT replaced COMMAND.COM with cmd.exe, a 32-bit program, and added the .cmd extension. cmd.exe is still the Command shell of Windows 10 and 11 and Windows Server, run in the console host or Windows Terminal; Microsoft’s command reference notes that “users seeking more advanced capabilities are encouraged to explore PowerShell”.

  • Command extensions are the larger language: if /i, defined, the comparison operators, cmdextversion, for /d /r /l /f, set /a and /p, %var:~n,m%, the %~ modifiers, call :label, goto :eof, setlocal options, exit /b, the dynamic variables, pushd and popd, mkdir creating whole paths and start. They are on by default, and are switched with cmd /e:on|off, the EnableExtensions registry value or setlocal enableextensions|disableextensions. SS64 gives CMDEXTVERSION 1 for Windows NT and 2 from Windows 2000.
  • Delayed expansion (!var!), off by default, is switched with cmd /v:on|off, a registry value or setlocal enabledelayedexpansion.
  • File name completion with Ctrl+D and Ctrl+F is off unless set with cmd /f:on or the CompletionChar registry values; it is an interactive feature, not part of scripts.
  • AutoRun. Commands in the AutoRun registry value run when each cmd.exe starts unless /d is given. A script that must not depend on them is run as cmd /d /c.
  • 16-bit programs run under NTVDM on 32-bit Windows with AUTOEXEC.NT and CONFIG.NT; 64-bit Windows has no NTVDM.
  • .cmd against .bat: see Errorlevel and exit codes.

OS/2 CMD.EXE

OS/2 uses .CMD files for both its batch language, much like DOS’s, and REXX programs, which must begin with a /* */ comment. The first line extproc hands a .CMD file to another program. Windows NT adopted the .cmd extension from OS/2. A file with this extension that starts with a comment is a REXX program; the viewer tells them apart that way and shows REXX without colour.

4DOS, 4OS2, 4NT and Take Command

JP Software made replacement shells: 4DOS for DOS, 4OS2 for OS/2, 4NT for Windows NT and later Take Command, which adds a console and an editor. Their batch files use .bat, or .btm (“batch to memory”), which is loaded once and so runs faster and can change the file on disk while it runs. They are supersets of the language above. Features from JP Software’s documentation, summarised here and not checked on a running copy:

  • Structured IFF condition THEN … ELSEIFF … ELSE … ENDIFF, DO loops, SWITCH, and GOSUB with RETURN.
  • Variable functions written %@name[args] (string, file and date functions) and internal variables such as %_cwd.
  • Aliases, command groups with ^ or & separators, and extended wildcards and redirection.

Take Command is still sold and updated by JP Software. The viewer colours a .btm file with the same scanner as a .bat, so the 4DOS-only commands stay plain.

Other implementations

  • FreeDOS – its COMMAND.COM (FreeCOM) follows MS-DOS and adds a few extensions of its own.
  • ReactOS – has a free cmd.exe written to match the Windows one.
  • Wine – ships a cmd.exe of its own that runs batch files on Linux and macOS.
  • DOSBox – its built-in shell runs a subset: .bat files with goto, if, for, call, shift and echo.
  • PowerShell – the successor, with .ps1 scripts. It runs a .bat by starting cmd.exe.

Not described

Known, not yet covered

  • Reference: the complete 4DOS and Take Command command set and function list; JP Software publishes its help.
  • Reference: the FreeCOM and DOSBox shells’ exact feature lists.
  • Viewer: 4DOS and Take Command commands and %@function[] forms are not coloured.

Unknown

  • Reference: which DOS and Windows release added each feature, and the 127-character COMMAND.COM limit, were not checked against a primary source. Most rows of the table are from memory of the documented behaviour and were not run on each interpreter for this page.