Command interpreter A command interpreter is the part of a computer operating system that understands and executes commands that are entered interactively by a human being or from a program. In some operating systems, the command interpreter is called the shell. How to use a command interpreter. A command line interpreter accept text via a keyboard input through a command-line imterface using command prompt, once the command is entered the CLI translates it into functions that the operating systen understands. The operating system then returns output to the user or performs a task based on the information it recieves. Examples. DEC's DIGITAL Command Language (DCL) in OpenVMS and RSX-11, the various Unix shells (sh, ksh, csh, tcsh, zsh, Bash, etc.), CP/M's CCP, DOS' COMMAND.COM, as well as the OS/2 and the Windows CMD.