Operating system: Difference between revisions

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In [[computing]], an '''operating system''' ('''OS''') is the [[system software]] responsible for the direct control and management of [[computer hardware|hardware]] and basic system operations, as well as running applications such as word processing programs and Web browsers.

==Introduction==

Colloquially, the term is most often used to mean all the software which "comes with" a [[computer]] system before any [[computer software|applications]] are installed.

The operating system ensures that other applications are able to use memory, input and output devices and have access to the [[file system]]. If multiple applications are running, the operating system schedules these such that all processes have sufficient processor time where possible and do not interfere with each other.

As of the beginning of [[2004]], the major operating systems in widespread use on [[personal computer]]s have consolidated into two families: the [[Microsoft Windows]] family and the [[UNIX]]-style family (which includes various definitions of Unix, [[GNU/Linux|Linux]] and [[Mac OS X]]).

UNIX is widely used in academic institutions and back-end implementations, while Windows is popular among home users as well as businesses for front-end use. On the client side, Windows is by far the most widely-used operating system with studies variously placing Microsoft's market share anywhere from 90-98%. Linux is widely used in [[web server]]s, and is making inroads into home and business environments. Mac OS X (which incorporated major parts of UNIX) and its predecessors are popular with a relatively small but loyal group of home users and multimedia designers.

[[Mainframe]] computers and [[embedded system]]s use a variety of different operating systems, many with no direct connection to Windows or UNIX.

== Examples of operating systems ==

* [[DOS]]

* [[Linux|GNU/Linux]]

* [[Mac OS]]

* [[Microsoft Windows|Windows]]

* [[UNIX]]

* More OS: [[List of operating systems]] (Please continue list there).

== Classifications and terminology ==

An operating system is conceptually broken into three sets of components: a user interface (which may consist of a [[graphical user interface]] and/or a [[command line interpreter]] or "shell"), low-level system utilities, and a [[Kernel (computers)|kernel]]--which is the heart of the operating system. As the name implies, the shell is an outer wrapper to the kernel, which in turn talks directly to the hardware.

Hardware <-> Kernel <-> Shell <-> Applications

In some operating systems the shell and the kernel are completely separate entities, allowing you to run varying combinations of shell and kernel (eg [[UNIX]]), in others their separation is only conceptual.

Kernel design ideologies include those of the [[kernel_(computers)#Monolithic kernels|monolithic kernel]], [[kernel_(computers)#Microkernels|microkernel]], and [[kernel_(computers)#Exokernels|exokernel]]. Traditional commercial systems such as [[UNIX]] and [[Microsoft Windows|Windows]], as well as the newer [[Linux]], use a [[monolithic]] approach, while the trend in more modern systems is to use a [[microkernel]] (such as in [[QNX]], [[BeOS]], [[Windows NT]] etc). The microkernel approach is also very popular among research OSes. Many [[embedded system]]s use ad-hoc exokernels.

==Related articles==

===General topics===

* [[History of operating systems]]

* [[List of operating systems]]

* [[Operating systems timeline]]

===Other topics===

* [[Hard disk drive partitioning]]

* [[LiveCD]] OS ([[Gnoppix]] and [[Knoppix]] [[Linux]]).

* [[monolithic kernel|monolithic]] [[kernel (computers)|kernel]] -- [[microkernel]] -- [[exokernel]] -- [[virtual machine]]

* asymmetric and symmetric [[multiprocessing]] (SMP) -- [[clustering]] -- [[distributed computing]]

* [[Operating system advocacy]]

* [[real-time operating system]] -- [[time-share]] -- [[Computer multitasking|multitasking]] -- [[embedded system]] -- [[single-user]] -- [[multi-user]]

* [[orthogonal persistence|orthogonally persistent]] -- capabilities versus [[access control list]]s

* [[object-oriented operating system]]

==External links==

* [http://www.cs.arizona.edu/people/bridges/os/full.html Operating Systems Projects]

* [http://cliki.tunes.org TUNES wiki, contains reviews of operating systems]

* [http://www.visual-opal.de How Operating Systems Work, shown by a tiny self-developed Operating System]

* [http://www.cbi.umn.edu/iterations/haigh.html Multicians.org and the History of Operating Systems]

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