Provides the means whereby a user can communicate with the computer, i.e. it provides a user interface . MAC-OS used by Macintosh computers. In the case of UNIX user commands are passed to the the computer using the keyboard. Creation, deletion and inspection of directories. Execution of programs.
Commands are simply calls to system programs which run in the same way as any other programs.
Logging in To begin using an operating system on a shared network such as that supported by the department of computer science you must first log in . When you login you will be prompted for your username and password . Your user name identifies you as a valid user of the system. You can not log in if you do not have a user name. Usernames are assigned by the system administrators - the people who manage the department's computer facilities.