The Operating System (OS) is a computer resource manager that manages all resources including the computer processor, memory, and I/O devices (keyboard, mouse, monitor, printers, etc). The OS provides orderly and controlled sharing of the resources by users or applications that need them. The OS hides the complexity of the underlying hardware and provides users and applications a better view (an abstraction) of the computer.

Common Operating Systems include DOS, Macintosh OS X, VMS, UNIX, and Windows.