Command Prompt

Command Prompt (executable name cmd.exe) is the Microsoft-supplied command-line interpreter on OS/2, Windows CE and on Windows NT-based operating systems (including Windows 2000, XP, Vista, 7, Server 2003 and Server 2008). It is the analog of COMMAND.COM in MS-DOS and Windows 9x (where it is called MS-DOS Prompt) systems, or of the Unix shells used on Unix-like systems.

Versions

Therese Stowell developed the initial version of cmd.exe for Windows NT.^[1] Although some old DOS commands are unsupported or have been changed (ex: the functionality of deltree was rolled into rd in the form of the /s parameter), cmd.exe still has a greater number of built-in commands.

Both the OS/2 and the Windows NT versions of cmd.exe have more detailed error messages than the blanket "Bad command or file name" (in the case of malformed commands) of command.com. In the OS/2 version of cmd.exe, errors are reported in the current language of the system, their text being taken from the system message files. The help command can then be issued with the error message number to obtain further information.

cmd.exe remains part of Windows Vista, Windows Server 2008, and Windows 7.

Technical information

Unlike COMMAND.COM, which is a DOS program, cmd.exe is a native program for the platform. This allows it to take advantage of features available to native programs on the platform that are otherwise unavailable to DOS programs. For example, since cmd.exe is a native text-mode application on OS/2, it can use real pipes in command pipelines, allowing both sides of the pipeline to run concurrently. As a result, it is possible to redirect the standard error in cmd.exe, unlike COMMAND.COM. (COMMAND.COM uses temporary files, and runs the two sides serially, one after the other.)

In reality, cmd.exe is a Windows program that acts as a DOS-like command line interpreter. It is generally compatible, but provides extensions which address some of the limitations of COMMAND.COM:

• SETLOCAL/ENDLOCAL commands limit the scope of changes to the environment
• internal CALL and GOTO labels lessen the need for individual batch files to perform parts of a task.
• filename-parsing extensions to the SET command are comparable to C shell.
• an expression-evaluation extensions is also provided in the SET command.
• an expansion of the FOR command to support parsing files and arbitrary sets in addition to filenames.
• use of arrow keys to scroll through command history (provided by DOSKey in COMMAND.COM)
• off-by-default path completion capabilities similar to bash tab completion
• a directory stack accessible with the PUSHD and POPD commands
• IF can perform case-insensitive comparisons and numeric equality and inequality comparisons in addition to case-sensitive string comparisons
• the ability to escape reserved characters by using the caret character (^)

The extensions can be disabled, providing a stricter compatibility mode.

See also

• Comparison of command shells
• List of DOS commands
• Virtual DOS machine (NTVDM)

References

External links

• MSDN Documentation for cmd.exe on Windows XP