Operating System

An operating system (OS) is system software that manages computer hardware and software resources, and provides common services for computer programs.

Definition

An operating system is difficult to define, but has been called "the layer of software that manages a computer's resources for its users and their applications". Operating systems include the software that is always running, called a kernel - but can include other software as well. The two other types of programs that can run on a computer are system programs - which are associated with the operating system, but may not be part of the kernel - and applications - all other software.