An operating system is a set of programs that controls how the hardware of a computer works.

An operating system provides a means of communication between the user and the computer, deals with the loading and running of applications programs and manages the transfer of data and files to and from peripheral devices.

The most widely used operating systems are called Windows 2000, MacOS (for Apple Mac computers), Novell Netware and UNIX.

The operating system that a computer has also determines what applications software will run on it.

Applications software will only work on a computer that has the operating system that it was designed to be used with. Applications software will not run on a computer that has a different operating system to the one that it was designed for.