The Computers: Software: (Operating Systems Software )

Operating systems (OSs) do many things: it is the block of software that runs in the memory of a computer which mediates between the hardware below and application(s) above; provides consistent access to various hardware for user programs such as applications and utilities; multiplexes hardware resources between two or more processes, programs, users; provides some common services to all software via an application programming (or protocol) interface (API); allocates memory and storage; schedules tasks. On this page, OSs are arranged in three groups and levels: 1) Top group: issues spanning multiple unrelated OSs. 2) Middle group: types or classes of OS, or OSs for which there are more than one instance of an OS of this name-type, an OS family. Operating Systems Software Computers.

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