An operating system (OS) is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system. A user cannot run an application program on the computer without an operating system, unless the application program is self booting.

Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting for cost allocation of processor time, mass storage, printing, and other resources.

For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between application programs and the computer hardware, although the application code is usually executed directly by the hardware and will frequently call the OS or be interrupted by it. Operating systems are found on almost any device that contains a computer—from cellular phones and video game consoles to supercomputers and web servers.

Examples of popular modern operating systems include Android, iOS, Linux, Mac OS X, BSD, all of which have their roots in Unix, and Microsoft Windows.

Noun

computer m. (plural computers)

1. computer

• calculader

• BIOS (10)
• Boot Managers (26)
• Consumer Information@ (0)
• Directories (5)

• Graphic Subsystems (822)
• Guides (4)
• History (5)
• Programming@ (20)

• Ada@ (0)
• BSD@ (208)
• Capability (3)
• Closed Source (1)
• Distributed@ (52)
• DOS@ (171)
• Education (7)
• Embedded (1)
• Extensible (4)
• Functional (2)
• Handheld (0)
• Hybrid Kernel@ (1)
• IBM@ (0)
• Java@ (9)
• Language-based@ (7)
• Lisp@ (1)
• Mainframe (234)
• Microkernel (91)
• Midrange (150)

• Monolithic (2)
• Network (117)
• Oberon@ (41)
• Object-Oriented (62)
• Open Source (7)
• Parallel (1)
• Persistent (1)
• POSIX (2)
• Quality of Service@ (6)
• Realtime (182)
• Reflective (0)
• Research (0)
• Single Address Space (11)
• Smalltalk@ (218)
• Submicrokernel (10)
• TRON@ (8)
• Unix (729)
• x86 (185)

• 2K@ (2)
• AIX@ (15)
• Amiga@ (9)
• Amoeba@ (2)
• Amstrad@ (5)
• Apple II@ (35)
• Archy@ (11)
• AtheOS@ (8)
• A-UX@ (11)
• BeOS@ (27)
• BSD-OS@ (1)
• ChorusOS@ (1)
• CPM (13)
• Croquet@ (16)
• Darwin@ (6)
• Data General@ (4)
• DexOS@ (0)
• Digital Unix@ (3)
• DLXOS@ (18)
• DragonFly BSD@ (9)
• DR-DOS@ (8)
• eCos@ (7)
• EPOC@ (43)
• Erlang@ (167)
• EROS@ (10)
• FreeBSD@ (62)
• FreeDOS@ (11)
• FreeRTOS@ (4)
• GEOS@ (10)
• GNU Hurd@ (10)
• HP-UX@ (6)
• Inferno@ (11)
• IRIX@ (3)
• KolibriOS@ (3)
• L4@ (12)
• Linux (1,954)
• LynxOS@ (3)
• Mac OS (483)
• Mach@ (26)
• MenuetOS@ (9)
• MicroC-OS@ (2)
• Microsoft Windows (502)
• MINIX@ (12)
• ML@ (1)

• MorphOS@ (9)
• MPE@ (70)
• Nemesis@ (3)
• NetBSD@ (32)
• NetWare@ (34)
• NeXT@ (10)
• Nucleus@ (6)
• OpenBSD@ (76)
• OS X@ (54)
• OS-2 (119)
• OS-400@ (89)
• OS-9@ (7)
• Palm OS@ (354)
• Pick@ (447)
• Plan 9@ (32)
• PRIMOS (4)
• PURE@ (2)
• QNX@ (13)
• ReactOS@ (8)
• REAL-32@ (4)
• REBOL-IOS@ (96)
• RISC OS@ (371)
• RTEMS@ (6)
• RxDOS@ (3)
• SCO@ (166)
• Self@ (12)
• SkyOS@ (3)
• Solaris@ (47)
• Squeak@ (81)
• Syllable@ (8)
• Symbian@ (74)
• THEOS (4)
• ThreadX@ (3)
• TI-99 4A (34)
• TinyOS@ (12)
• TUNES@ (3)
• V2 OS@ (1)
• VMS@ (57)
• VSE@ (6)
• VSTa@ (0)
• VxWorks@ (2)
• Xinu@ (5)
• z-OS@ (46)
• z-VM@ (12)

• Computers: Programming: Languages (11,228)

• OSNews: Exploring the Future of Computing
  osnews.com
  Weblog style online magazine on operating systems and computing environments. Daily updates, reader forum with many comments.
• How Stuff Works: Operating Systems
  howstuffworks.com
  Unbiased enlightening tutorial with impartial description of how OSs work, and many related links.
• Internet Operating System Counter
  leb.net
  Statistics on Internet OS use, WWW, FTP, and News servers. Over 940,000 hosts checked in this 1999 survey.
• Operating System - Growing article, with links to many related topics. Wikipedia.

• Usenet comp.os.misc - news: - Google Groups
• Usenet comp.os.research - news: - Google Groups