Command (computing)

In computing, a command is a directive to a computer program to perform a specific task. Commands are the fundamental means by which users and other programs interact with the operating system or application. They serve as instructions that trigger a defined action or sequence of actions.

Commands can be issued through various interfaces, including command-line interfaces (CLIs), graphical user interfaces (GUIs), and application programming interfaces (APIs).

• Command-line interfaces (CLIs): In CLIs, commands are typically typed as text strings, often followed by arguments or options that modify the command's behavior. The operating system or application interprets the text and executes the corresponding function.

• Graphical user interfaces (GUIs): In GUIs, commands are often initiated through visual elements like buttons, menus, or icons. Clicking on these elements triggers a predefined command that the application executes. The underlying translation between the user's action and the machine-executable code is handled by the GUI system.

• Application Programming Interfaces (APIs): APIs allow programs to communicate with each other by sending commands. These commands are often structured according to specific protocols (e.g., HTTP requests, function calls) and allow software to access and utilize the functionality of other software components.

The specific commands available depend entirely on the operating system, programming language, or application in question. Common examples include commands for file management (creating, deleting, renaming files), process control (starting, stopping programs), network communication (sending and receiving data), and system configuration (setting system parameters).

The interpretation and execution of commands are handled by a command interpreter (also known as a shell in CLI environments). The command interpreter parses the command, identifies the appropriate function to execute, and passes any provided arguments to that function. After the function completes, the interpreter typically returns control to the user or program that issued the command.