COMMAND.COM
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Template:Mono is the default command-line interpreter for MS-DOS, Windows 95, Windows 98 and Windows Me. In the case of DOS, it is the default user interface as well. It has an additional role as the usual first program run after boot (init process). As a shell, Template:Mono has two distinct modes of operation: interactive mode and batch mode. Internal commands are commands stored directly inside the Template:Mono binary; thus, they are always available, but can only be executed directly from the command interpreter.Template:Citation needed
Description
Template:Mono's successor on OS/2 and Windows NT systems is cmd.exe, although COMMAND.COM is available in virtual DOS machines on IA-32 versions of those operating systems as well. The Template:Mono filename was also used by Template:Ill (DCP), an MS-DOS derivative by the former East German VEB Robotron.<ref name="DCP_2016" />
Template:Mono is a DOS program. Programs launched from Template:Mono are DOS programs that use the DOS API to communicate with the disk operating system. The compatible command processor under FreeDOS is sometimes also called FreeCom.
Operating modes
As a shell, Template:Mono has two distinct modes of operation. The first is interactive mode, in which the user types commands which are then executed immediately. The second is batch mode, which executes a predefined sequence of commands stored as a text file with the .BAT extension.
Template:AnchorInternal commands
Internal commands are commands stored directly inside the Template:Mono binary. Thus, they are always available but can only be executed directly from the command interpreter.
All commands are executed after the Template:Keypress key is pressed at the end of the line. Template:Mono is not case-sensitive, meaning commands can be typed in any mixture of upper and lower case.
- [[BREAK (DOS command)|Template:Mono]]
- Controls the handling of program interruption with Template:Keypress or Template:Keypress.
- [[CHCP (command)|Template:Mono]]
- Displays or changes the current system code page.
- [[CHDIR|Template:Mono, Template:Mono]]
- Changes the current working directory or displays the current directory.
- [[CLS (DOS command)|Template:Mono]]
- Clears the screen.
- [[COPY (DOS command)|Template:Mono]]
- Copies one file to another (if the destination file already exists, MS-DOS asks whether to replace it). (See also XCOPY, an external command that could also copy directory trees).
- [[CTTY (DOS command)|Template:Mono]]
- Defines the device to use for input and output.
- [[DATE (command)|Template:Mono]]
- Display and set the date of the system.
- [[DEL (command)|Template:Mono, Template:Mono]]
- Deletes a file. When used on a directory, deletes all files inside the directory only. In comparison, the external command Template:Mono deletes all subdirectories and files inside a directory as well as the directory itself.
- [[DIR (command)|Template:Mono]]
- Lists the files in the specified directory.
- [[ECHO (command)|Template:Mono]]
- Toggles whether text is displayed (Template:Codett) or not (Template:Codett). Also displays text on the screen (Template:Codett).
- [[EXIT (command)|Template:Mono]]
- Exits from Template:Mono and returns to the program which launched it.
- Template:Mono
- Enables or disables the return of long filenames by the Template:Mono command. (Windows 9x).Template:Citation needed
- [[LOADHIGH|Template:Mono, Template:Mono]]
- Loads a program into upper memory (Template:Codett in DR DOS).
- [[LOCK (DOS command)|Template:Mono]]
- Enables external programs to perform low-level disk access to a volume. (MS-DOS 7.1 and Windows 9x only)Template:Citation needed
- [[MKDIR|Template:Mono, Template:Mono]]
- Creates a new directory.
- [[PATH (DOS command)|Template:Mono]]
- Displays or changes the value of the Template:Mono environment variable which controls the places where Template:Mono will search for executable files.
- [[PROMPT (DOS command)|Template:Mono]]
- Displays or change the value of the Template:Mono environment variable which controls the appearance of the prompt.
- [[REN (command)|Template:Mono, Template:Mono]]
- Renames a file or directory.
- [[RMDIR|Template:Mono, Template:Mono]]
- Removes an empty directory.
- [[SET (DOS command)|Template:Mono]]
- Sets the value of an environment variable; without arguments, shows all defined environment variables.
- [[TIME (command)|Template:Mono]]
- Display and set the time of the system.
- Template:Mono
- Display the fully expanded physical name of a file, resolving [[ASSIGN (DOS command)|Template:Mono]], [[JOIN (DOS command)|Template:Mono]] and SUBST logical filesystem mappings.<ref name="Paul_1997_NWDOSTIP"/>
- [[TYPE (DOS command)|Template:Mono]]
- Display the content of a file on the console.
- [[UNLOCK (DOS command)|Template:Mono]]
- Disables low-level disk access. (MS-DOS 7.1 and Windows 9x only)Template:Citation needed
- [[VER (command)|Template:Mono]]
- Displays the version of the operating system.
- [[VERIFY (DOS command)|Template:Mono]]
- Enable or disable verification of writing for files.
- [[VOL (command)|Template:Mono]]
- Shows information about a volume.
Batch file commands
Control structures are mostly used inside batch files, although they can also be used interactively.<ref name="Caldera_1998_USER_CH7" /><ref name="Paul_1997_NWDOSTIP" />
- Template:Monolabel
- Defines a target for Template:Mono.
- [[CALL (DOS command)|Template:Mono]]
- Executes another batch file and returns to the old one and continues.
- [[FOR (DOS command)|Template:Mono]]
- Iteration: repeats a command for each out of a specified set of files.
- Template:Mono
- Moves execution to a specified label. Labels are specified at the beginning of a line, with a colon (Template:Codett).
- [[IF (DOS command)|Template:Mono]]
- Conditional statement, allows branching of the program execution.
- [[PAUSE (DOS command)|Template:Mono]]
- Halts execution of the program and displays a message asking the user to press any key to continue.
- [[REM (DOS command)|Template:Mono]]
- comment: any text following this command is ignored.
- [[SHIFT (DOS command)|Template:Mono]]
- Replaces each of the replacement parameters with the subsequent one (e.g. Template:Codett with Template:Codett, Template:Codett with Template:Codett, etc.).
IF command
On exit, all external commands submit a return code (a value between Template:Mono and Template:Mono) to the calling program. Most programs have a certain convention for their return codes (for instance, 0 for a successful execution).<ref name="Paul_1997_BATTIPS"/><ref name="FD_2003_Errorlevel"/><ref name="Paul_2003_Exitcodes"/><ref name="Allen_2005"/>
If a program was invoked by Template:Mono, the internal IF command with its Template:Mono conditional can be used to test on error conditions of the last invoked external program.Template:Citation needed
Under Template:Mono, internal commands do not establish a new value.Template:Citation needed
Variables
Batch files for Template:Mono can have four kinds of variables:
- Environment variables: These have the Template:Mono form and are associated with values with the SET statement. Before DOS 3 Template:Mono will only expand environment variables in batch mode; that is, not interactively at the command prompt.Template:Citation needed
- Replacement parameters: These have the form Template:Mono, Template:Mono...Template:Mono, and initially contain the command name and the first nine command-line parameters passed to the script (e.g., if the invoking command was Template:Kbd, then Template:Mono is Template:Mono, Template:Mono is Template:Mono and Template:Mono is Template:Mono). The parameters to the right of the ninth can be mapped into range by using the SHIFT statement.Template:Citation needed
- Loop variables: Used in loops, they have the Template:Mono format when run in batch files. These variables are defined solely within a specific FOR statement, and iterate over a certain set of values defined in that FOR statement.Template:Citation needed
- Under Novell DOS 7, OpenDOS 7.01, DR-DOS 7.02 and higher, Template:Mono also supports a number of system information variables,<ref name="Caldera_1998_USER_CH7"/><ref name="Caldera_1998_USER"/><ref name="Paul_1997_NWDOSTIP"/> a feature earlier found in 4DOS 3.00 and higher<ref name="4DOS_8.00_HELP"/> as well as in Multiuser DOS,<ref name="Paul_1997_NWDOSTIP"/> although most of the supported variable names differ.
Redirection, piping, and chaining
Because DOS is a single-tasking operating system, piping is achieved by running commands sequentially, redirecting to and from a temporary file.Template:Citation needed Template:Mono makes no provision for redirecting the standard error channel.Template:Citation needed
command < filename- Redirect standard input from a file or device
command > filename- Redirect standard output, overwriting target file if it exists.
command >> filename- Redirect standard output, appending to target file if it exists.
command1 | command2- Pipe standard output from command1 to standard input of command2
command1 ¶ command2- Commands separated by ASCII-20 (¶, invoked by Template:Keypress) are executed in sequence (chaining of commands).<ref name="Paul_1997_NWDOSTIP"/> In other words, first command1 is executed until termination, then command2.<ref name="Paul_1997_NWDOSTIP"/> This is an undocumented feature in Template:Mono of MS-DOS/PC DOS 5.0 and higher.<ref name="Paul_1997_NWDOSTIP"/> It is also supported by Template:Mono of the Windows NT family as well as by DR-DOS 7.07. All versions of DR-DOS Template:Mono already supported a similar internal function utilizing an exclamation mark (!) instead (a feature originally derived from Concurrent DOS and Multiuser DOS) - in the single-user line this feature was only available internally (in built-in startup scripts like "!DATE!TIME") and indirectly through DOSKEY's $T parameter to avoid problems with ! as a valid filename character.<ref name="Paul_1997_NWDOSTIP"/> 4DOS supports a configurable command line separator (4DOS.INI CommandSep= or SETDOS /C), which defaults to ^.<ref name="4DOS_8.00_HELP"/> Template:Mono in newer versions of Windows NT also supports an <syntaxhighlight lang="text" class="" style="" inline="1">&</syntaxhighlight> separator for compatibility with the cmd syntax in OS/2 and the Windows NT family.<ref name="4DOS_8.00_HELP"/> (cmd does not support the ¶ separator.)
Limitations
Generally, the command line length in interactive mode is limited to 126 characters.<ref name="Paul_1997_MSDOS"/><ref name="Paul_1997_4DOSTIP"/><ref name="Schulman_1994_Undocumented-DOS"/> In MS-DOS 6.22, the command line length in interactive mode is limited to 127 characters.Template:Citation needed
In popular culture
- The message "Loading Template:Mono" can be seen on a HUD view of the Terminator and the internal viewport of RoboCop when he reboots.Template:Citation needed
- In the animated children's TV series ReBoot, which takes place inside computers, the leader of a system (the equivalent of a city) is called the Template:Mono.<ref name=filmcomment>Template:Cite news</ref>
See also
- List of DOS commands
- Comparison of command shells
- cmd.exe — command-line interpreter in various Windows and OS/2 systems
- Template:Hlist — starts the command processor as the first process
- SHELL (CONFIG.SYS directive) — to override default command processor
- COMSPEC (environment variable) — set by Template:Mono to reload transient portion of itself
- CMDLINE (environment variable) — set by COMMAND.COM to pass long command lines to external programs
- Template:Hlist — third-party replacement command processors
- DOSSHELL / ViewMAX — alternative DOS shells
- Template:Hlist — have similar command processors not named Template:Mono
- PC-MOS/386 — has a similar command processor also named Template:Mono
- Transient Program Area — memory available for use either by the running application or the transient portion of Template:Mono
- SpartaDOS X — a similar implementation for Atari computers
- PowerShell
References
Further reading
External links
- Template:Github - Source code to COMMAND.COM version A067 released by Microsoft as part of MS-DOS 4.0
- Template:GitHub – Source code to COMMAND.COM version 2.11 released by Microsoft as part of MS-DOS 2.0
- Template:GitHub – Source code to COMMAND.COM version 1.17 released by Microsoft as part of MS-DOS 1.25
- FreeCom – COMMAND.COM implementation of FreeDOS
Template:Microsoft Windows components Template:Windows commands Template:DOS system files