In
computing, a command is a directive to a computer program to perform a specific task. It may be issued via a
command-line interface
A command-line interpreter or command-line processor uses a command-line interface (CLI) to receive commands from a user in the form of lines of text. This provides a means of setting parameters for the environment, invoking executables and pro ...
, such as a
shell, or as input to a network service as part of a
network protocol, or as an event in a
graphical user interface triggered by the user selecting an option in a
menu
In a restaurant, the menu is a list of food and beverages offered to customers and the prices. A menu may be à la carte – which presents a list of options from which customers choose – or table d'hôte, in which case a pre-established seque ...
.
Specifically, the term ''command'' is used in
imperative computer languages. The name arises because
statements in these languages are usually written in a manner similar to the
imperative mood used in many
natural language
In neuropsychology, linguistics, and philosophy of language, a natural language or ordinary language is any language that has evolved naturally in humans through use and repetition without conscious planning or premeditation. Natural languages ...
s. If one views a statement in an
imperative language
In computer science, imperative programming is a programming paradigm of software that uses statements that change a program's state. In much the same way that the imperative mood in natural languages expresses commands, an imperative program c ...
as being like a sentence in a natural language, then a command is generally like a verb in such a language.
Many programs allow specially formatted arguments, known as flags or options, which modify the default behaviour of the program, while further
arguments may provide objects, such as files, to act on. As an analogy to a natural language, the flags are adverbs, while the other arguments are
object
Object may refer to:
General meanings
* Object (philosophy), a thing, being, or concept
** Object (abstract), an object which does not exist at any particular time or place
** Physical object, an identifiable collection of matter
* Goal, an ai ...
s.
Examples
Here are some commands given to a
command-line interpreter (
Unix shell).
The following command changes the user's working position in the
directory tree to the directory ''/home/pete''. The utility program is ''
cd'' and the argument is ''/home/pete'':
cd /home/pete
The following command prints the text ''Hello World'' on the
standard output stream, which, in this case, just prints the text on the screen. The program name is
echo and the argument is "Hello World". The quotes are used to prevent ''Hello'' and ''World'' being treated as separate tokens:
echo "Hello World"
The following commands are equivalent. They list files in the directory ''/bin''. The program is ''
ls'', having three flags (''l'', ''t'', ''r''), and the argument is the directory ''
/bin'':
ls -l -t -r /bin
ls -ltr /bin
The following command displays the contents of the files ''ch1.txt'' and ''ch2.txt''. The program name is ''
cat'', having two file name arguments:
cat ch1.txt ch2.txt
Here are some commands for the
DOS,
OS/2 and
Microsoft Windows
Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...
command prompt processor. The following command displays the contents of the file ''readme.txt''. The program name is ''
type
Type may refer to:
Science and technology Computing
* Typing, producing text via a keyboard, typewriter, etc.
* Data type, collection of values used for computations.
* File type
* TYPE (DOS command), a command to display contents of a file.
* Ty ...
'' and the argument is ''readme.txt''.
type readme.txt
The following command lists the contents of the current directory. The program name is ''
dir'', and ''Q'' is a flag requesting that the owner of each file also be listed.
dir /Q
See also
*
Gesture recognition
Gesture recognition is a topic in computer science and language technology with the goal of interpreting human gestures via mathematical algorithms. It is a subdiscipline of computer vision. Gestures can originate from any bodily motion or sta ...
*
List of Unix commands
*
List of DOS commands
*
Formal grammar
References
External links
commandfrom
FOLDOCWindows Commands , Microsoft Docs
{{Windows commands
User interfaces
Computing terminology