computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes, and development of both hardware and software. Computing has scientific, ...

, a command is a directive to a computer program to perform a specific task. It may be issued via a command-line interface, such as a

shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses ** Thin-shell structure Science Biology * Seashell, a hard o ...

, or as input to a network service as part of a

network protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchroniza ...

, or as an event in a

graphical user interface The GUI ( "UI" by itself is still usually pronounced . or ), graphical user interface, is a form of user interface that allows users to interact with electronic devices through graphical icons and audio indicator such as primary notation, inst ...

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 language A computer language is a formal language used to communicate with a computer. Types of computer languages include: * Construction language – all forms of communication by which a human can specify an executable problem solution to a comput ...

s. The name arises because

statements Statement or statements may refer to: Common uses *Statement (computer science), the smallest standalone element of an imperative programming language *Statement (logic), declarative sentence that is either true or false *Statement, a declarative ...

in these languages are usually written in a manner similar to the

imperative mood The imperative mood is a grammatical mood that forms a command or request. The imperative mood is used to demand or require that an action be performed. It is usually found only in the present tense, second person. To form the imperative mood, ...

used in many natural languages. If one views a statement in an imperative language 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 An argument is a statement or group of statements called premises intended to determine the degree of truth or acceptability of another statement called conclusion. Arguments can be studied from three main perspectives: the logical, the dialectic ...

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 ...

Examples

Here are some commands given to a

command-line interpreter 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 ...

(

Unix shell A Unix shell is a command-line interpreter or shell that provides a command line user interface for Unix-like operating systems. The shell is both an interactive command language and a scripting language, and is used by the operating syste ...

). The following command changes the user's working position in the

directory tree In computing, a directory is a file system cataloging structure which contains references to other computer files, and possibly other directories. On many computers, directories are known as folders, or drawers, analogous to a workbench or the t ...

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 In computer programming, standard streams are interconnected input and output communication channels between a computer program and its environment when it begins execution. The three input/output (I/O) connections are called standard input (stdin ...

stream, which, in this case, just prints the text on the screen. The program name is

echo In audio signal processing and acoustics, an echo is a reflection of sound that arrives at the listener with a delay after the direct sound. The delay is directly proportional to the distance of the reflecting surface from the source and the lis ...

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 The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...

'', having two file name arguments: cat ch1.txt ch2.txt Here are some commands for the

DOS DOS is shorthand for the MS-DOS and IBM PC DOS family of operating systems. DOS may also refer to: Computing * Data over signalling (DoS), multiplexing data onto a signalling channel * Denial-of-service attack (DoS), an attack on a communicat ...

OS/2 OS/2 (Operating System/2) is a series of computer operating systems, initially created by Microsoft and IBM under the leadership of IBM software designer Ed Iacobucci. As a result of a feud between the two companies over how to position OS/2 r ...

and Microsoft Windows

command prompt Command Prompt, also known as cmd.exe or cmd, is the default command-line interpreter for the OS/2, eComStation, ArcaOS, Microsoft Windows (Windows NT family and Windows CE family), and ReactOS operating systems. On Windows CE .NET 4.2, W ...

processor. The following command displays the contents of the file ''readme.txt''. The program name is '' type'' 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

References

External links

command
from

FOLDOC The Free On-line Dictionary of Computing (FOLDOC) is an online, searchable, encyclopedic dictionary of computing subjects. History FOLDOC was founded in 1985 by Denis Howe and was hosted by Imperial College London. In May 2015, the site was up ...

Windows Commands , Microsoft Docs
{{Windows commands User interfaces Computing terminology

Examples

See also

References

External links