As mentioned above, users generally use either the command line interface or the GUI to interact with the operating system.
Some operating systems include the command interpreter in the kernel. Some, such as the popular Windows and Linux operating systems, use the command interpreter as a special program that runs when a user logs on or a job is initiated.
in Windows, this is the MS-DOS prompt.
Linux has more options. The command interpreter in Linux is known as a shell. The most commonly used shell is the Bash shell, but others such as the Korn shell, C shell, and Bourne shell exist. Most shells provide similar functionality, personal preference usually dictates which shell is best.
The main function of the command utility is to receive and execute the next user generated command.
- Many commands are intended to manipulate files.
- Operating systems such as UNIX implements commands through system programs. Often these programs are stored as text files, which allows programmers to add additional functionality to the utility.