Other names | MS-DOS Prompt, Windows Command Interpreter |
---|---|
Developer(s) | Seattle Computer Products, IBM, Microsoft, The Software Link, Datalight, Novell, Caldera |
Initial release | 1980 |
Written in | x86 assembly language [1] |
Operating system | |
Platform | 16-bit x86 |
Successor | cmd.exe |
Type | Command-line interpreter |
COMMAND.COM 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, COMMAND.COM has two distinct modes of operation: interactive mode and batch mode. Internal commands are commands stored directly inside the COMMAND.COM binary; thus, they are always available, but can only be executed directly from the command interpreter.
COMMAND.COM 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.[ citation needed ] It has an additional role as the usual first program run after boot (init process), hence being responsible for setting up the system by running the AUTOEXEC.BAT configuration file, and being the ancestor of all processes.[ citation needed ]
COMMAND.COM'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 COMMAND.COM filename was also used by Disk Control Program [ de ] (DCP), an MS-DOS derivative by the former East German VEB Robotron. [2]
COMMAND.COM is a DOS program. Programs launched from COMMAND.COM are DOS programs that use the DOS API to communicate with the disk operating system. The compatible command processor under FreeDOS is sometimes also named FreeCom.
As a shell, COMMAND.COM 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.
Internal commands are commands stored directly inside the COMMAND.COM binary. Thus, they are always available but can only be executed directly from the command interpreter.
All commands are executed after the ↵ Enter key is pressed at the end of the line. COMMAND.COM is not case-sensitive, meaning commands can be typed in any mixture of upper and lower case.
ECHO ON
) or not (ECHO OFF
). Also displays text on the screen (ECHO text
).HILOAD
in DR DOS).Control structures are mostly used inside batch files, although they can also be used interactively. [4] [3]
:likethis
).%0
with %1
, %1
with %2
, etc.).On exit, all external commands submit a return code (a value between 0 and 255) to the calling program. Most programs have a certain convention for their return codes (for instance, 0 for a successful execution). [5] [6] [7] [8]
If a program was invoked by COMMAND.COM, the internal IF command with its ERRORLEVEL conditional can be used to test on error conditions of the last invoked external program.[ citation needed ]
Under COMMAND.COM, internal commands do not establish a new value.[ citation needed ]
Batch files for COMMAND.COM can have four kinds of variables:
Because DOS is a single-tasking operating system, piping is achieved by running commands sequentially, redirecting to and from a temporary file.[ citation needed ] COMMAND.COM makes no provision for redirecting the standard error channel.[ citation needed ]
command < filename
command > filename
command >> filename
command1 | command2
command1 ¶ command2
&
separator for compatibility with the cmd syntax in OS/2 and the Windows NT family. [10] (cmd does not support the ¶ separator.)Generally, the command line length in interactive mode is limited to 126 characters. [11] [12] [13] In MS-DOS 6.22, the command line length in interactive mode is limited to 127 characters.[ citation needed ]
In computer data storage, drive letter assignment is the process of assigning alphabetical identifiers to volumes. Unlike the concept of UNIX mount points, where volumes are named and located arbitrarily in a single hierarchical namespace, drive letter assignment allows multiple highest-level namespaces. Drive letter assignment is thus a process of using letters to name the roots of the "forest" representing the file system; each volume holds an independent "tree".
In computing, the working directory of a process is a directory of a hierarchical file system, if any, dynamically associated with the process. It is sometimes called the current working directory (CWD), e.g. the BSD getcwd function, or just current directory. When a process refers to a file using a simple file name or relative path (as opposed to a file designated by a full path from a root directory), the reference is interpreted relative to the working directory of the process. So for example a process with working directory /rabbit-shoes that asks to create the file foo.txt will end up creating the file /rabbit-shoes/foo.txt.
4DOS is a command-line interpreter by JP Software, designed to replace the default command interpreter COMMAND.COM
in Microsoft DOS and Windows. It was written by Rex C. Conn and Tom Rawson and first released in 1989. Compared to the default, it has a large number of enhancements.
An environment variable is a user-definable value that can affect the way running processes will behave on a computer. Environment variables are part of the environment in which a process runs. For example, a running process can query the value of the TEMP environment variable to discover a suitable location to store temporary files, or the HOME or USERPROFILE variable to find the directory structure owned by the user running the process.
A path is a string of characters used to uniquely identify a location in a directory structure. It is composed by following the directory tree hierarchy in which components, separated by a delimiting character, represent each directory. The delimiting character is most commonly the slash ("/"), the backslash character ("\"), or colon (":"), though some operating systems may use a different delimiter. Paths are used extensively in computer science to represent the directory/file relationships common in modern operating systems and are essential in the construction of Uniform Resource Locators (URLs). Resources can be represented by either absolute or relative paths.
A COM file is a type of simple executable file. On the Digital Equipment Corporation (DEC) VAX operating systems of the 1970s, .COM
was used as a filename extension for text files containing commands to be issued to the operating system. With the introduction of Digital Research's CP/M, the type of files commonly associated with COM extension changed to that of executable files. This convention was later carried over to DOS. Even when complemented by the more general EXE file format for executables, the compact COM files remained viable and frequently used under DOS.
CONFIG.SYS is the primary configuration file for the DOS and OS/2 operating systems. It is a special ASCII text file that contains user-accessible setup or configuration directives evaluated by the operating system's DOS BIOS during boot. CONFIG.SYS was introduced with DOS 2.0.
DOSKEY is a command for DOS, IBM OS/2, Microsoft Windows, and ReactOS that adds command history, macro functionality, and improved editing features to the command-line interpreters COMMAND.COM
and cmd.exe
.
AUTOEXEC.BAT
is a system file that was originally on DOS-type operating systems. It is a plain-text batch file in the root directory of the boot device. The name of the file is an abbreviation of "automatic execution", which describes its function in automatically executing commands on system startup; the filename was coined in response to the 8.3 filename limitations of the FAT file system family.
Command-line completion is a common feature of command-line interpreters, in which the program automatically fills in partially typed commands.
The Program Segment Prefix (PSP) is a data structure used in DOS systems to store the state of a program. It resembles the Zero Page in the CP/M operating system. The PSP has the following structure:
IO.SYS is an essential part of MS-DOS and Windows 9x. It contains the default MS-DOS device drivers and the DOS initialization program.
A command shell is a command-line interface to interact with and manipulate a computer's operating system.
Long filename (LFN) support is Microsoft's backward-compatible extension of the 8.3 filename naming scheme used in DOS. Long filenames can be more descriptive, including longer filename extensions such as .jpeg
, .tiff
, .html
, and .xhtml
that are common on other operating systems, rather than specialized shortened names such as .jpg
, .tif
, .htm
, or .xht
. The standard has been common with File Allocation Table (FAT) filesystems since its first implementation in Windows NT 3.5 of 1994.
Take Command Console (TCC), formerly known as 4DOS for Windows NT (4NT), is a command-line interpreter by JP Software, designed as a substitute for the default command interpreter in Microsoft Windows, CMD.EXE.
Computer hardware or software is said to be bug compatible if it exactly replicates an undesirable feature of a previous version. The phrase is found in the Jargon File.
A batch file is a script file in DOS, OS/2 and Microsoft Windows. It consists of a series of commands to be executed by the command-line interpreter, stored in a plain text file. A batch file may contain any command the interpreter accepts interactively and use constructs that enable conditional branching and looping within the batch file, such as IF
, FOR
, and GOTO
labels. The term "batch" is from batch processing, meaning "non-interactive execution", though a batch file might not process a batch of multiple data.
In computing, type is a command in various command-line interpreters (shells) such as COMMAND.COM
, cmd.exe
, 4DOS/4NT and Windows PowerShell used to display the contents of specified files on the computer terminal. The analogous Unix command is cat.
A command-line interface (CLI) is a means of interacting with a computer program by inputting lines of text called command-lines. Command-line interfaces emerged in the mid-1960s, on computer terminals, as an interactive and more user-friendly alternative to the non-interactive interface available with punched cards.
{{cite book}}
: |work=
ignored (help) (NB. The provided link points to a HTML-converted version of the NWDOSTIP.TXT
, which is part of the MPDOSTIP.ZIP
collection.) {{cite book}}
: |work=
ignored (help) (NB. BATTIPS.TXT is part of MPDOSTIP.ZIP. The provided link points to an HTML-converted older version of the BATTIPS.TXT file.) [...] Multiple Commands: You can type several commands on the same command line, separated by a caret [^]. For example, if you know you want to copy all of your .TXT files to drive A: and then run CHKDSK to be sure that drive A's file structure is in good shape, you could enter the following command:C:\>COPY *.TXT A: ^ CHKDSK A:
You may put as many commands on the command line as you wish, as long as the total length of the command line does not exceed 511 characters. You can use multiple commands in aliases and batch files as well as at the command line. If you don't like using the default command separator, you can pick another character using theSETDOS /C
command or the CommandSep directive in 4DOS.INI. [...]SETDOS /C:
(Compound character) This option sets the character used for separating multiple commands on the same line. The default is the caret [^]. You cannot use any of the redirection characters [<>|], or the blank, tab, comma, or equal sign as the command separator. The command separator is saved by SETLOCAL and restored by ENDLOCAL. This example changes the separator to a tilde [~]:C:\>SETDOS /C~
(You can specify either the character itself, or its ASCII code as a decimal number, or a hexadecimal number preceded by 0x.) [...] CommandSep = c (^): This is the character used to separate multiple commands on the same line. [...] Special Character Compatibility: If you use two or more of our products, or if you want to share aliases and batch files with users of different products, you need to be aware of the differences in three important characters: the Command Separator [...], the Escape Character [...], and the Parameter Character [...]. The default values of each of these characters in each product is shown in the following chart: [...] Product, Separator, Escape Parameter [...] 4DOS: ^, ↑, & [...] 4OS2, 4NT, Take Command: &, ^, $ [...] (The up-arrow [↑] represents the ASCII Ctrl-X character, numeric value 24.) [...]— Brothers, Hardin; Rawson, Tom; Conn, Rex C.; Paul, Matthias R.; Dye, Charles E.; Georgiev, Luchezar I. (2002-02-27). 4DOS 8.00 online help.
{{cite book}}
: |work=
ignored (help) (NB. MSDOSTIP.TXT is part of MPDOSTIP.ZIP, maintained up to 2001 and distributed on many sites at the time. The provided link points to a HTML-converted older version of the MSDOSTIP.TXT file.) 4DOS5TIP.TXT
file, which is part of the MPDOSTIP.ZIP
collection.) [...] all MS-DOS versions prior to Windows 95 [...] used a COM style COMMAND.COM file which has a special signature at the start of the file [...] queried by the MS-DOS BIOS before it loads the shell, but not by the DR-DOS BIOS [...] COMMAND.COM would [...] check that it is running on the "correct" DOS version, so if you would load their COMMAND.COM under DR-DOS, you would receive a "Bad version" error message and their COMMAND.COM would exit, so DR-DOS would [...] display an error message "Bad or missing command interpreter" (if DR-DOS was trying to load the SHELL= command processor after having finished CONFIG.SYS processing). In this case, you could enter the path to a valid DR-DOS COMMAND.COM (C:\DRDOS\COMMAND.COM) and everything was fine. Now, things have changed since MS-DOS 7.0 [...] COMMAND.COM has internally become an EXE style file, so there is no magic [...] signature [...] to check [...] thus no way for DR-DOS to rule out an incompatible COMMAND.COM. Further, their COMMAND.COM no longer does any version checks, but [...] does not work under DR-DOS [...] just crashes [...] the PC DOS COMMAND.COM works fine under DR-DOS [...]
Paul, Matthias R. (2004-06-17). "Re: Random Lockups with DR-DOS 7.03". FidoNet conference: ALT_DOS. Archived from the original on 2019-04-28. Retrieved 2019-04-28.