a program that makes the facilities of the operating system available to interactive users
a text-based command line driven interface to the host machine's operating system - the most basic level of access for a regular user
The command language that provides a user interface to the UNIX operating system.
Unix is the largest multi-user general-purpose operating system; it includes a wide range of operating-system 'adaptations' including Linux. The 'shell' is Unix's command interpreter for the operating system; somewhat similar to Windows' DOS box.
A Unix shell, also called "the command line", provides the traditional user interface for the Unix operating system and for Unix-like systems. Users direct the operation of the computer by entering command input as text for a shell to execute. Within the Microsoft Windows suite of operating systems the analogous program is command.com, or cmd.exe for Windows NT-based operating systems.
