operating system

Software which directs the overall activity of a computer (e.g. MS-DOS , Windows , Linux , etcetera).

Software that controls the execution of computer programs. It may provide scheduling, debugging, input and output control, accounting, storage assignment, data management, and related service. Sometimes called supervisor, executive, monitor, or master control program depending on the computer manufacturer.

The operating system allows a computer's hardware devices to be accessed by programs. For instance, it allows data to be organized on a computer's disks in the form of a file system and it delivers the co-ordinate positions of a mouse to programs as the mouse is moved. Operating systems also make it possible for multiple programs to be run concurrently, or multiple users to share a single machine. See concurrency.

A special program that runs on the bare machine and hides the gory details of managing processes and devices. Usually used in a looser sense to indicate a particular culture of programming. The loose sense can be used at varying levels of specificity. At one extreme, you might say that all versions of Unix and Unix-lookalikes are the same operating system (upsetting many people, especially lawyers and other advocates). At the other extreme, you could say this particular version of this particular vendor's operating system is different from any other version of this or any other vendor's operating system. Perl is much more portable across operating systems than many other languages. See also "architecture" and "platform".

Software that directly controls the operations of a computer

An integrated collection of routines that service the sequencing and processing of programs by a computer. Note: An operating system may provide many services, such as resource allocation, scheduling, input/output control, and data management. Although operating systems are predominantly software, partial or complete hardware implementations may be made in the form of firmware.