The command interpreter is the part of an operating system responsible for processing and executing textual commands entered by a computer user at the Windows command line interface or MS-DOS. It executes commands like setting dynamic variables, or loading and executing other files.
In Windows operating systems, the command interpreter is referred to as the command shell. The command shell facilitates direct communication between the operating system and the User. The main command line interpreter in Windows is Command Prompt. In UNIX systems, command operators are called shells. UNIX shells typically have unique control structures and syntax. This allows shell scripts to be used to automate repetitive tasks.