Command processor

A command processor (or command line interpreter) is a program to which a user of a computer gives commands, which the command processor parses, and then takes the appropriate action to make happen.

That appropriate action may be something performed internally to the command processor, or the command processor may load another program (e.g. a compiler), or it may cause the creation of a whole new process which is then set to execute some program.

Originally, all input to the command processor was typed by the user on a serial line terminal; with the advent of the mouse, and the graphical interface, the user may instead click on an icon.

The most well-known command interpreter at this point is the shell of UNIX, which is based on the similar program of the Multics operating system.