cmd.exe

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Command Prompt (cmd.exe)
Command prompt icon (windows).png
Command Prompt in Windows 10
Command Prompt in Windows 10
Other namesWindows Command Processor
Developer(s)Microsoft, IBM, ReactOS contributors
Operating systemOS/2, Microsoft Windows, ReactOS
ReplacesCOMMAND.COM
TypeCommand-line interpreter
Websitedocs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-xp/bb490890(v=technet.10)

CMD, cmd (after its command name) or cmd.exe (after its executable file name), also known as Command Prompt (after the default window title), is the command-line interpreter in the OS/2, eComStation, Windows NT, Windows CE, and ReactOS operating systems. It is the counterpart of COMMAND.COM in DOS and Windows 9x systems, and analogous to the Unix shells used on Unix-like systems. The initial version of cmd.exe for Windows NT was developed by Therese Stowell.[1]

Operation[edit]

cmd.exe interacts with the user through a command-line interface. In Windows, this interface is implemented through the Win32 console. cmd.exe may take advantage of features available to native programs of its own platform. For example, in 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 stream. (COMMAND.COM uses temporary files, and runs the two sides serially, one after the other.)

Comparison with COMMAND.COM[edit]

In Windows, cmd.exe is mostly compatible with COMMAND.COM but provides the following extensions over it:

  • More detailed error messages than the blanket "Bad command or file name" (in the case of malformed commands) of COMMAND.COM. In OS/2, errors are reported in the chosen 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.
  • Supports using of arrow keys to scroll through command history. (Under DOS this function was only available under DR DOS (through HISTORY) and later via a external component called DOSKEY.)
  • Adds command-line completion for file and folder paths.
  • Treats the caret character (^) as the escape character; the character following it is to be taken literally. There are special characters in cmd.exe and COMMAND.COM (e.g. "<", ">" and "|") that are meant to alter the behavior of the command line processor. The caret character forces the command line processor to interpret them literally.
  • Supports delayed variable expansion[further explanation needed] (Windows 2000 and later), fixing DOS idioms that made using control structures hard and complex.[2] The extensions can be disabled, providing a stricter compatibility mode.

Internal commands have also been improved:

  • The DELTREE command was merged into the RD command, as part of its /S switch.
  • SetLocal and EndLocal commands limit the scope of changes to the environment. Changes made to the command line environment after SetLocal commands are local to the batch file. EndLocal command restores the previous settings.[3]
  • The Call command allows subroutines within batch file. The Call command in COMMAND.COM only supports calling external batch files.
  • File name parser extensions to the Set command are comparable with C shell.[further explanation needed]
  • The Set command can perform expression evaluation.
  • An expansion of the For command supports parsing files and arbitrary sets in addition to file names.
  • The new PushD and PopD commands provide access past navigated paths similar to "forward" and "back" buttons in a web browser or File Explorer.
  • The conditional IF command can perform case-insensitive comparisons and numeric equality and inequality comparisons in addition to case-sensitive string comparisons. (This was available in DR-DOS, but not in PC DOS or MS-DOS.)

See also[edit]

References[edit]

  1. ^ Zachary, G. Pascal (1994). Showstopper! The Breakneck Race to Create Windows NT and the Next Generation at Microsoft. The Free Press. ISBN 0-02-935671-7.
  2. ^ "Windows 2000 delayed environment variable expansion". Windows IT Pro. Retrieved 2015-07-13.
  3. ^ "Setlocal". TechNet. Microsoft. Retrieved 2015-01-13.

Further reading[edit]