tag:blogger.com,1999:blog-88166653269602242722024-02-08T04:16:37.893-08:00operating systemin here, you can learn more about operating system. for example; you can learn about how to use it, what is operating system, and maybe you can get all the easy way about operating system. and more...indrahttp://www.blogger.com/profile/06942992661543821548noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-8816665326960224272.post-46249057548726315942012-02-22T21:22:00.000-08:002012-02-22T21:26:12.341-08:00karya indraaaasssset x-3 BIOS coy<div style="color: black;">
<b><br /></b></div>
<div class="MsoNormal" style="background: none repeat scroll 0% 0% rgb(68, 102, 102); color: black; line-height: 18.75pt; margin-bottom: 0in;">
<b><span lang="IN" style="font-family: "Trebuchet MS","sans-serif"; font-size: 12pt;">Fungsi
Menu BIOS</span></b></div>
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<td style="background: olive; border: inset white 1.0pt; padding: 0in 0in 0in 0in; width: 35.0%;" width="35%"><div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; text-align: center;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Standard CMOS
Features</span></b></div>
</td>
<td style="background: #CCCC00; border-left: none; border: inset 1.0pt; padding: 0in 0in 0in 0in; width: 65.0%;" width="65%"><div class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Menu
dasar konfigurasi waktu, tanggal, <i>floppy drive</i>, dll</span></b></div>
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<td style="background: olive; border-top: none; border: inset 1.0pt; padding: 0in 0in 0in 0in; width: 35.0%;" width="35%"><div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; text-align: center;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Advanced BIOS
Features</span></b></div>
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<td style="background: #CCCC00; border-bottom: inset 1.0pt; border-left: none; border-right: inset 1.0pt; border-top: none; padding: 0in 0in 0in 0in; width: 65.0%;" width="65%"><div class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Mengatur
<i>setting system</i> misalnya menentukan <i>booting</i> pertama,
menentukan sistem keamananan, mempercepat proses<i>booting</i>, dll</span></b></div>
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<td style="background: olive; border-top: none; border: inset 1.0pt; padding: 0in 0in 0in 0in; width: 35.0%;" width="35%"><div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; text-align: center;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Advanced Chipset
Features</span></b></div>
</td>
<td style="background: #CCCC00; border-bottom: inset 1.0pt; border-left: none; border-right: inset 1.0pt; border-top: none; padding: 0in 0in 0in 0in; width: 65.0%;" width="65%"><div class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Mengatur
<i>system</i> konfigurasi <i>memory</i>, VGA, dll</span></b></div>
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<td style="background: olive; border-top: none; border: inset 1.0pt; padding: 0in 0in 0in 0in; width: 35.0%;" width="35%"><div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; text-align: center;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Integrated
Peripherial</span></b></div>
</td>
<td style="background: #CCCC00; border-bottom: inset 1.0pt; border-left: none; border-right: inset 1.0pt; border-top: none; padding: 0in 0in 0in 0in; width: 65.0%;" width="65%"><div class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Mengatur
<i>setting hardware</i> yang sudah terpasang pada <i>mainboard/On board</i></span></b></div>
</td>
</tr>
<tr style="mso-yfti-irow: 4;">
<td style="background: olive; border-top: none; border: inset 1.0pt; padding: 0in 0in 0in 0in; width: 35.0%;" width="35%"><div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; text-align: center;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Power Management
Setup</span></b></div>
</td>
<td style="background: #CCCC00; border-bottom: inset 1.0pt; border-left: none; border-right: inset 1.0pt; border-top: none; padding: 0in 0in 0in 0in; width: 65.0%;" width="65%"><div class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Mengatur
<i>system power</i> untuk monitor, <i>hard disk</i>, dll</span></b></div>
</td>
</tr>
<tr style="mso-yfti-irow: 5;">
<td style="background: olive; border-top: none; border: inset 1.0pt; padding: 0in 0in 0in 0in; width: 35.0%;" width="35%"><div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; text-align: center;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">PnP / PCI Configurations</span></b></div>
</td>
<td style="background: #CCCC00; border-bottom: inset 1.0pt; border-left: none; border-right: inset 1.0pt; border-top: none; padding: 0in 0in 0in 0in; width: 65.0%;" width="65%"><div class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Mengatur
peralatan dengan jalur PCI dan perangkat yang dikenalkan secara <i>default</i>oleh
komputer</span></b></div>
</td>
</tr>
<tr style="mso-yfti-irow: 6;">
<td style="background: olive; border-top: none; border: inset 1.0pt; padding: 0in 0in 0in 0in; width: 35.0%;" width="35%"><div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; text-align: center;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">PC Helath Status</span></b></div>
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<td style="background: #CCCC00; border-bottom: inset 1.0pt; border-left: none; border-right: inset 1.0pt; border-top: none; padding: 0in 0in 0in 0in; width: 65.0%;" width="65%"><div class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Untuk
mengetahui kondisi suhu prosesor, putaran kipas, dll</span></b></div>
</td>
</tr>
<tr style="mso-yfti-irow: 7;">
<td style="background: olive; border-top: none; border: inset 1.0pt; padding: 0in 0in 0in 0in; width: 35.0%;" width="35%"><div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; text-align: center;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Frequency / Voltage
Control</span></b></div>
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<td style="background: #CCCC00; border-bottom: inset 1.0pt; border-left: none; border-right: inset 1.0pt; border-top: none; padding: 0in 0in 0in 0in; width: 65.0%;" width="65%"><div class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Mengatur<i>
frequency</i> control Prosesor</span></b></div>
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<td style="background: olive; border-top: none; border: inset 1.0pt; padding: 0in 0in 0in 0in; width: 35.0%;" width="35%"><div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; text-align: center;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Load High
Performance Defaults</span></b></div>
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<td style="background: #CCCC00; border-bottom: inset 1.0pt; border-left: none; border-right: inset 1.0pt; border-top: none; padding: 0in 0in 0in 0in; width: 65.0%;" width="65%"><div class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in;">
<b><i><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Setting</span></i><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;"> optimal yang terbaik dan ketat dengan mengabaikan stabilitas komputer</span></b></div>
</td>
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<tr style="mso-yfti-irow: 9;">
<td style="background: olive; border-top: none; border: inset 1.0pt; padding: 0in 0in 0in 0in; width: 35.0%;" width="35%"><div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; text-align: center;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Load Optimized
Defaults</span></b></div>
</td>
<td style="background: #CCCC00; border-bottom: inset 1.0pt; border-left: none; border-right: inset 1.0pt; border-top: none; padding: 0in 0in 0in 0in; width: 65.0%;" width="65%"><div class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Mengatur
<i>setting</i> optimal standar dan tidak terlalu ketat</span></b></div>
</td>
</tr>
<tr style="mso-yfti-irow: 10;">
<td style="background: olive; border-top: none; border: inset 1.0pt; padding: 0in 0in 0in 0in; width: 35.0%;" width="35%"><div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; text-align: center;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Set Supervisor
Password</span></b></div>
</td>
<td style="background: #CCCC00; border-bottom: inset 1.0pt; border-left: none; border-right: inset 1.0pt; border-top: none; padding: 0in 0in 0in 0in; width: 65.0%;" width="65%"><div class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Memberi <i>password</i>
dengan Akses <i>full </i>tanpa batas</span></b></div>
</td>
</tr>
<tr style="mso-yfti-irow: 11;">
<td style="background: olive; border-top: none; border: inset 1.0pt; padding: 0in 0in 0in 0in; width: 35.0%;" width="35%"><div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; text-align: center;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Set User Password</span></b></div>
</td>
<td style="background: #CCCC00; border-bottom: inset 1.0pt; border-left: none; border-right: inset 1.0pt; border-top: none; padding: 0in 0in 0in 0in; width: 65.0%;" width="65%"><div class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Memberi <i>password</i>
dengan akses terbatas</span></b></div>
</td>
</tr>
<tr style="mso-yfti-irow: 12;">
<td style="background: olive; border-top: none; border: inset 1.0pt; padding: 0in 0in 0in 0in; width: 35.0%;" width="35%"><div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; text-align: center;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Save & Exit
Setup</span></b></div>
</td>
<td style="background: #CCCC00; border-bottom: inset 1.0pt; border-left: none; border-right: inset 1.0pt; border-top: none; padding: 0in 0in 0in 0in; width: 65.0%;" width="65%"><div class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Keluar
dan menyimpan konfigurasi <i>setting</i></span></b></div>
</td>
</tr>
<tr style="mso-yfti-irow: 13; mso-yfti-lastrow: yes;">
<td style="background: olive; border-top: none; border: inset 1.0pt; padding: 0in 0in 0in 0in; width: 35.0%;" width="35%"><div align="center" class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; text-align: center;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Exit Without Saving</span></b></div>
</td>
<td style="background: #CCCC00; border-bottom: inset 1.0pt; border-left: none; border-right: inset 1.0pt; border-top: none; padding: 0in 0in 0in 0in; width: 65.0%;" width="65%"><div class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in;">
<b><span lang="IN" style="font-family: "Arial","sans-serif"; font-size: 12pt;">Keluar
tanpa menyimpan konfigurasi <i>setting</i></span></b></div>
</td>
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</tbody></table>
</td>
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<div class="MsoNormal" style="color: black;">
<b><br /></b></div>indrahttp://www.blogger.com/profile/06942992661543821548noreply@blogger.com0tag:blogger.com,1999:blog-8816665326960224272.post-55703449291995953632012-02-02T04:03:00.000-08:002012-02-02T04:03:22.470-08:00operating system<h1 class="firstHeading" id="firstHeading">
Operating system</h1>
<div id="siteSub">
From Wikipedia, the free encyclopedia</div>
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<th class="" style="font-size: 145%; font-weight: bold; line-height: 1.2em; padding: 0.2em 0.4em 0.2em;"><b class="selflink">Operating systems</b></th>
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<map id="ImageMap_1_315718635" name="ImageMap_1_315718635">
<area alt="User" coords="1,1,165,59" href="http://en.wikipedia.org/wiki/User_%28computing%29" shape="rect" title="User"></area>
<area alt="Application" coords="1,60,165,119" href="http://en.wikipedia.org/wiki/Application_software" shape="rect" title="Application"></area>
<area alt="Operating System" coords="1,119,165,178" href="http://en.wikipedia.org/wiki/Operating_system" shape="rect" title="Operating System"></area>
<area alt="Hardware" coords="1,179,165,237" href="http://en.wikipedia.org/wiki/Personal_computer_hardware" shape="rect" title="Hardware"></area></map><img alt="Operating system placement.svg" height="244" src="http://upload.wikimedia.org/wikipedia/commons/thumb/e/e1/Operating_system_placement.svg/165px-Operating_system_placement.svg.png" usemap="#ImageMap_1_315718635" width="165" />
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<div style="margin-left: 145px; margin-top: -20px; text-align: left;">
<a href="http://en.wikipedia.org/wiki/File:Operating_system_placement.svg" title="About this image"><img alt="About this image" src="http://en.wikipedia.org/w/extensions/ImageMap/desc-20.png" style="border: none;" /></a></div>
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<td class="" style="font-weight: bold; padding-top: 0.2em; padding-top: 0.4em;">Common features</td>
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<td style="padding-bottom: 0.2em; text-align: left;"><ul>
<li><a href="http://en.wikipedia.org/wiki/Process_management_%28computing%29" title="Process management (computing)">Process management</a></li>
<li><a href="http://en.wikipedia.org/wiki/Interrupt" title="Interrupt">Interrupts</a></li>
<li><a href="http://en.wikipedia.org/wiki/Memory_management" title="Memory management">Memory management</a></li>
<li><a href="http://en.wikipedia.org/wiki/File_system" title="File system">File system</a></li>
<li><a href="http://en.wikipedia.org/wiki/Device_driver" title="Device driver">Device drivers</a></li>
<li><a href="http://en.wikipedia.org/wiki/Computer_network" title="Computer network">Networking (TCP/IP, UDP)</a></li>
<li><a href="http://en.wikipedia.org/wiki/Computer_security" title="Computer security">Security (Process/Memory protection)</a></li>
<li><a href="http://en.wikipedia.org/wiki/Input/output" title="Input/output">I/O</a></li>
</ul>
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<td style="font-size: 115%; text-align: right;"><div class="noprint plainlinks hlist navbar">
<ul>
<li class="nv-view"><a href="http://en.wikipedia.org/wiki/Template:OS" title="Template:OS"><span title="View this template">v</span></a></li>
<li class="nv-talk"><a href="http://en.wikipedia.org/wiki/Template_talk:OS" title="Template talk:OS"><span title="Discuss this template">d</span></a></li>
<li class="nv-edit"><a class="external text" href="http://en.wikipedia.org/w/index.php?title=Template:OS&action=edit"><span title="Edit this template">e</span></a></li>
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<td class="mbox-text">This article <b>needs additional <a href="http://en.wikipedia.org/wiki/Wikipedia:Citing_sources#Inline_citations" title="Wikipedia:Citing sources">citations</a> for <a href="http://en.wikipedia.org/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">verification</a></b>. Please help <a class="external text" href="http://en.wikipedia.org/w/index.php?title=Operating_system&action=edit">improve this article</a> by adding citations to <a href="http://en.wikipedia.org/wiki/Wikipedia:Identifying_reliable_sources" title="Wikipedia:Identifying reliable sources">reliable sources</a>. Unsourced material may be <a href="http://en.wikipedia.org/wiki/Template:Citation_needed" title="Template:Citation needed">challenged</a> and <a href="http://en.wikipedia.org/wiki/Wikipedia:Verifiability#Burden_of_evidence" title="Wikipedia:Verifiability">removed</a>. <small><i>(October 2011)</i></small></td>
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An <b>operating system</b> (<b>OS</b>) is a set of <a href="http://en.wikipedia.org/wiki/Computer_program" title="Computer program">programs</a> that manage <a href="http://en.wikipedia.org/wiki/Computer_hardware" title="Computer hardware">computer hardware</a> resources and provide common services for <a href="http://en.wikipedia.org/wiki/Application_software" title="Application software">application software</a>. The operating system is the most important type of <a href="http://en.wikipedia.org/wiki/System_software" title="System software">system software</a>
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.<br />
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.<br />
For hardware functions such as input and output and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Dynamic_memory_allocation" title="Dynamic memory allocation">memory allocation</a>, the operating system acts as an intermediary between application programs and the computer hardware,<sup class="reference" id="cite_ref-0"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-0">[1]</a></sup><sup class="reference" id="cite_ref-1"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-1">[2]</a></sup>
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 <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Cellular_phone" title="Cellular phone">cellular phones</a> and <a href="http://en.wikipedia.org/wiki/Video_game_console" title="Video game console">video game consoles</a> to <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Supercomputers" title="Supercomputers">supercomputers</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Web_servers" title="Web servers">web servers</a>.<br />
Examples of popular modern operating systems include <a href="http://en.wikipedia.org/wiki/Android_%28operating_system%29" title="Android (operating system)">Android</a>, <a href="http://en.wikipedia.org/wiki/IOS" title="IOS">iOS</a>, <a href="http://en.wikipedia.org/wiki/Linux" title="Linux">Linux</a>, <a href="http://en.wikipedia.org/wiki/Mac_OS_X" title="Mac OS X">Mac OS X</a>, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/BSD" title="BSD">BSD</a>, all of which have their roots in <a href="http://en.wikipedia.org/wiki/Unix" title="Unix">Unix</a>, and <a href="http://en.wikipedia.org/wiki/Microsoft_Windows" title="Microsoft Windows">Microsoft Windows</a>.<sup class="reference" id="cite_ref-netapplications_2-0"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-netapplications-2"></a></sup><br />
<table class="toc" id="toc">
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<td><div id="toctitle">
<h2>
Contents</h2>
<span class="toctoggle"></span></div>
<ul>
<li class="toclevel-1 tocsection-1"><a href="http://en.wikipedia.org/wiki/Operating_system#Types"><span class="tocnumber">1</span> <span class="toctext">Types</span></a></li>
<li class="toclevel-1 tocsection-2"><a href="http://en.wikipedia.org/wiki/Operating_system#Summary"><span class="tocnumber">2</span> <span class="toctext">Summary</span></a></li>
<li class="toclevel-1 tocsection-3"><a href="http://en.wikipedia.org/wiki/Operating_system#History"><span class="tocnumber">3</span> <span class="toctext">History</span></a>
<ul>
<li class="toclevel-2 tocsection-4"><a href="http://en.wikipedia.org/wiki/Operating_system#Mainframes"><span class="tocnumber">3.1</span> <span class="toctext">Mainframes</span></a></li>
<li class="toclevel-2 tocsection-5"><a href="http://en.wikipedia.org/wiki/Operating_system#Microcomputers"><span class="tocnumber">3.2</span> <span class="toctext">Microcomputers</span></a></li>
</ul>
</li>
<li class="toclevel-1 tocsection-6"><a href="http://en.wikipedia.org/wiki/Operating_system#Examples_of_operating_systems"><span class="tocnumber">4</span> <span class="toctext">Examples of operating systems</span></a>
<ul>
<li class="toclevel-2 tocsection-7"><a href="http://en.wikipedia.org/wiki/Operating_system#Unix_and_Unix-like_operating_systems"><span class="tocnumber">4.1</span> <span class="toctext">Unix and Unix-like operating systems</span></a>
<ul>
<li class="toclevel-3 tocsection-8"><a href="http://en.wikipedia.org/wiki/Operating_system#BSD_and_its_descendants"><span class="tocnumber">4.1.1</span> <span class="toctext">BSD and its descendants</span></a>
<ul>
<li class="toclevel-4 tocsection-9"><a href="http://en.wikipedia.org/wiki/Operating_system#Mac_OS_X"><span class="tocnumber">4.1.1.1</span> <span class="toctext">Mac OS X</span></a></li>
</ul>
</li>
<li class="toclevel-3 tocsection-10"><a href="http://en.wikipedia.org/wiki/Operating_system#Plan_9"><span class="tocnumber">4.1.2</span> <span class="toctext">Plan 9</span></a></li>
<li class="toclevel-3 tocsection-11"><a href="http://en.wikipedia.org/wiki/Operating_system#Linux_and_GNU"><span class="tocnumber">4.1.3</span> <span class="toctext">Linux and GNU</span></a>
<ul>
<li class="toclevel-4 tocsection-12"><a href="http://en.wikipedia.org/wiki/Operating_system#Google_Chrome_OS"><span class="tocnumber">4.1.3.1</span> <span class="toctext">Google Chrome OS</span></a></li>
</ul>
</li>
</ul>
</li>
<li class="toclevel-2 tocsection-13"><a href="http://en.wikipedia.org/wiki/Operating_system#AmigaOS"><span class="tocnumber">4.2</span> <span class="toctext">AmigaOS</span></a></li>
<li class="toclevel-2 tocsection-14"><a href="http://en.wikipedia.org/wiki/Operating_system#Microsoft_Windows"><span class="tocnumber">4.3</span> <span class="toctext">Microsoft Windows</span></a></li>
<li class="toclevel-2 tocsection-15"><a href="http://en.wikipedia.org/wiki/Operating_system#Other"><span class="tocnumber">4.4</span> <span class="toctext">Other</span></a></li>
</ul>
</li>
<li class="toclevel-1 tocsection-16"><a href="http://en.wikipedia.org/wiki/Operating_system#Components"><span class="tocnumber">5</span> <span class="toctext">Components</span></a>
<ul>
<li class="toclevel-2 tocsection-17"><a href="http://en.wikipedia.org/wiki/Operating_system#Kernel"><span class="tocnumber">5.1</span> <span class="toctext">Kernel</span></a>
<ul>
<li class="toclevel-3 tocsection-18"><a href="http://en.wikipedia.org/wiki/Operating_system#Program_execution"><span class="tocnumber">5.1.1</span> <span class="toctext">Program execution</span></a></li>
<li class="toclevel-3 tocsection-19"><a href="http://en.wikipedia.org/wiki/Operating_system#Interrupts"><span class="tocnumber">5.1.2</span> <span class="toctext">Interrupts</span></a></li>
<li class="toclevel-3 tocsection-20"><a href="http://en.wikipedia.org/wiki/Operating_system#Modes"><span class="tocnumber">5.1.3</span> <span class="toctext">Modes</span></a></li>
<li class="toclevel-3 tocsection-21"><a href="http://en.wikipedia.org/wiki/Operating_system#Memory_management"><span class="tocnumber">5.1.4</span> <span class="toctext">Memory management</span></a></li>
<li class="toclevel-3 tocsection-22"><a href="http://en.wikipedia.org/wiki/Operating_system#Virtual_memory"><span class="tocnumber">5.1.5</span> <span class="toctext">Virtual memory</span></a></li>
<li class="toclevel-3 tocsection-23"><a href="http://en.wikipedia.org/wiki/Operating_system#Multitasking"><span class="tocnumber">5.1.6</span> <span class="toctext">Multitasking</span></a></li>
<li class="toclevel-3 tocsection-24"><a href="http://en.wikipedia.org/wiki/Operating_system#Disk_access_and_file_systems"><span class="tocnumber">5.1.7</span> <span class="toctext">Disk access and file systems</span></a></li>
<li class="toclevel-3 tocsection-25"><a href="http://en.wikipedia.org/wiki/Operating_system#Device_drivers"><span class="tocnumber">5.1.8</span> <span class="toctext">Device drivers</span></a></li>
</ul>
</li>
<li class="toclevel-2 tocsection-26"><a href="http://en.wikipedia.org/wiki/Operating_system#Networking"><span class="tocnumber">5.2</span> <span class="toctext">Networking</span></a></li>
<li class="toclevel-2 tocsection-27"><a href="http://en.wikipedia.org/wiki/Operating_system#Security"><span class="tocnumber">5.3</span> <span class="toctext">Security</span></a></li>
<li class="toclevel-2 tocsection-28"><a href="http://en.wikipedia.org/wiki/Operating_system#User_interface"><span class="tocnumber">5.4</span> <span class="toctext">User interface</span></a>
<ul>
<li class="toclevel-3 tocsection-29"><a href="http://en.wikipedia.org/wiki/Operating_system#Graphical_user_interfaces"><span class="tocnumber">5.4.1</span> <span class="toctext">Graphical user interfaces</span></a></li>
</ul>
</li>
</ul>
</li>
<li class="toclevel-1 tocsection-30"><a href="http://en.wikipedia.org/wiki/Operating_system#Real-time_operating_systems"><span class="tocnumber">6</span> <span class="toctext">Real-time operating systems</span></a></li>
<li class="toclevel-1 tocsection-31"><a href="http://en.wikipedia.org/wiki/Operating_system#Operating_system_development_as_a_hobby"><span class="tocnumber">7</span> <span class="toctext">Operating system development as a hobby</span></a></li>
<li class="toclevel-1 tocsection-32"><a href="http://en.wikipedia.org/wiki/Operating_system#Diversity_of_operating_systems_and_portability"><span class="tocnumber">8</span> <span class="toctext">Diversity of operating systems and portability</span></a></li>
<li class="toclevel-1 tocsection-33"><a href="http://en.wikipedia.org/wiki/Operating_system#See_also"><span class="tocnumber">9</span> <span class="toctext">See also</span></a></li>
<li class="toclevel-1 tocsection-34"><a href="http://en.wikipedia.org/wiki/Operating_system#References"><span class="tocnumber">10</span> <span class="toctext">References</span></a></li>
<li class="toclevel-1 tocsection-35"><a href="http://en.wikipedia.org/wiki/Operating_system#Further_reading"><span class="tocnumber">11</span> <span class="toctext">Further reading</span></a></li>
<li class="toclevel-1 tocsection-36"><a href="http://en.wikipedia.org/wiki/Operating_system#External_links"><span class="tocnumber">12</span> <span class="toctext">External link</span></a></li>
</ul>
</td>
</tr>
</tbody></table>
<h2>
<span class="editsection"></span> <span class="mw-headline" id="Types">Types</span></h2>
<dl>
<dt>Real-time</dt>
<dd>A <a href="http://en.wikipedia.org/wiki/Real-time_operating_system" title="Real-time operating system">real-time operating system</a>
is a multitasking operating system that aims at executing real-time
applications. Real-time operating systems often use specialized
scheduling algorithms so that they can achieve a deterministic nature of
behavior. The main objective of real-time operating systems is their
quick and predictable response to events. They have an event-driven or
time-sharing design and often aspects of both. An event-driven system
switches between tasks based on their priorities or external events
while time-sharing operating systems switch tasks based on clock
interrupts.</dd></dl>
<dl>
<dt>Multi-user vs. Single-user</dt>
<dd>A multi-user operating system allows multiple users to access a
computer system concurrently. Time-sharing system can be classified as
multi-user systems as they enable a multiple user access to a computer
through the sharing of time. Single-user operating systems, as opposed
to a multi-user operating system, are usable by a single user at a time.
Being able to have multiple accounts on a Windows operating system does
not make it a multi-user system. Rather, only the network administrator
is the real user. But for a Unix-like operating system, it is possible
for two users to login at a time and this capability of the OS makes it a
multi-user operating system.</dd></dl>
<dl>
<dt>Multi-tasking vs. Single-tasking</dt>
<dd>When only a single program is allowed to run at a time, the system
is grouped under a single-tasking system. However, when the operating
system allows the execution of multiple tasks at one time, it is
classified as a multi-tasking operating system. Multi-tasking can be of
two types: pre-emptive or co-operative. In pre-emptive multitasking, the
operating system slices the CPU time and dedicates one slot to each of
the programs. Unix-like operating systems such as Solaris and Linux
support pre-emptive multitasking, as does AmigaOS. Cooperative
multitasking is achieved by relying on each process to give time to the
other processes in a defined manner. MS Windows prior to Windows 2000
and Mac OS prior to OS X used to support cooperative multitasking.</dd></dl>
<dl>
<dt>Distributed</dt>
<dd>A distributed operating system manages a group of independent
computers and makes them appear to be a single computer. The development
of networked computers that could be linked and communicate with each
other gave rise to distributed computing. Distributed computations are
carried out on more than one machine. When computers in a group work in
cooperation, they make a distributed system.</dd></dl>
<dl>
<dt>Embedded</dt>
<dd><a href="http://en.wikipedia.org/wiki/Embedded_system" title="Embedded system">Embedded</a>
operating systems are designed to be used in embedded computer systems.
They are designed to operate on small machines like PDAs with less
autonomy. They are able to operate with a limited number of resources.
They are very compact and extremely efficient by design. Windows CE and
Minix 3 are some examples of embedded operating systems.</dd></dl>
<h2>
<span class="editsection"></span> <span class="mw-headline" id="Summary">Summary</span></h2>
Early computers were built to perform a series of single tasks, like a
calculator. Operating systems did not exist in their modern and more
complex forms until the early 1960s.<sup class="reference" id="cite_ref-3"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-3">[4]</a></sup> Some operating system features were developed in the 1950s, such as <a href="http://en.wikipedia.org/wiki/Resident_monitor" title="Resident monitor">resident monitor</a>
programs that could automatically run different application programs in
succession to speed up processing. Hardware features were added that
enabled use of <a href="http://en.wikipedia.org/wiki/Runtime_library" title="Runtime library">runtime libraries</a>, <a href="http://en.wikipedia.org/wiki/Programmable_Interrupt_Controller" title="Programmable Interrupt Controller">interrupts</a>, and <a href="http://en.wikipedia.org/wiki/Parallel_processing" title="Parallel processing">parallel processing</a>. When personal computers by companies such as <a href="http://en.wikipedia.org/wiki/Apple_Inc." title="Apple Inc.">Apple Inc.</a>, <a href="http://en.wikipedia.org/wiki/Atari" title="Atari">Atari</a>, <a href="http://en.wikipedia.org/wiki/IBM" title="IBM">IBM</a> and <a href="http://en.wikipedia.org/wiki/Amiga" title="Amiga">Amiga</a>
became popular in the 1980s, vendors added operating system features
that had previously become widely used on mainframe and mini computers.
Later, many features such as <a href="http://en.wikipedia.org/wiki/Graphical_user_interface" title="Graphical user interface">graphical user interface</a> were developed specifically for personal computer operating systems.<br />
An operating system consists of many parts. One of the most important components is the <a href="http://en.wikipedia.org/wiki/Kernel_%28computing%29" title="Kernel (computing)">kernel</a>,
which controls low-level processes that the average user usually cannot
see: it controls how memory is read and written, the order in which
processes are executed, how information is received and sent by devices
like the <a href="http://en.wikipedia.org/wiki/Computer_monitor" title="Computer monitor">monitor</a>, keyboard and mouse, and decides how to interpret information received from networks. The <a href="http://en.wikipedia.org/wiki/User_interface" title="User interface">user interface</a>
is a component that interacts with the computer user directly, allowing
them to control and use programs. The user interface may be <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Graphical_User_Interface" title="Graphical User Interface">graphical with icons and a desktop</a>, or <a href="http://en.wikipedia.org/wiki/Command-line_interface" title="Command-line interface">textual, with a command line</a>. <a href="http://en.wikipedia.org/wiki/Application_programming_interface" title="Application programming interface">Application programming interfaces</a>
provide services and code libraries that let applications developers
write modular code reusing well defined programming sequences in user
space libraries or in the operating system itself. Which features are
considered part of the operating system is defined differently in
various operating systems. For example, Microsoft Windows considers its
user interface to be part of the operating system, while many versions
of Linux do not.<br />
<h2>
<span class="editsection"></span> <span class="mw-headline" id="History">History</span></h2>
<div class="rellink relarticle mainarticle">
Main article: <a href="http://en.wikipedia.org/wiki/History_of_operating_systems" title="History of operating systems">History of operating systems</a></div>
In the 1940s, the earliest electronic digital systems had no
operating systems. Electronic systems of this time were so primitive
compared to those of today that instructions were often entered into the
system one bit at a time on rows of mechanical switches or by jumper
wires on plug boards. These were special-purpose systems that, for
example, generated ballistics tables for the military or controlled the
printing of payroll checks from data on punched paper cards. After
programmable general purpose computers were invented, machine languages
(consisting of strings of the binary digits 0 and 1 on punched paper
tape) were introduced that speed up the programming process (Stern,
1981).<br />
<div class="thumb tright">
<div class="thumbinner" style="width: 222px;">
<a class="image" href="http://en.wikipedia.org/wiki/File:IBM360-65-1.corestore.jpg"><img alt="" class="thumbimage" height="293" src="http://upload.wikimedia.org/wikipedia/commons/thumb/6/6a/IBM360-65-1.corestore.jpg/220px-IBM360-65-1.corestore.jpg" width="220" /></a>
<br />
<div class="thumbcaption">
<div class="magnify">
<a class="internal" href="http://en.wikipedia.org/wiki/File:IBM360-65-1.corestore.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.18/common/images/magnify-clip.png" width="15" /></a></div>
<a class="mw-redirect" href="http://en.wikipedia.org/wiki/OS/360" title="OS/360">OS/360</a> was used on most IBM mainframe computers beginning in 1966, including the computers that helped NASA put a man on the moon.</div>
</div>
</div>
In the early 1950s, a computer could execute only one program at a
time. Each user had sole use of the computer for a limited period of
time and would arrive at a scheduled time with program and data on
punched paper cards and/or punched tape. The program would be loaded
into the machine, and the machine would be set to work until the program
completed or crashed. Programs could generally be debugged via a front
panel using toggle switches and panel lights. It is said that <a href="http://en.wikipedia.org/wiki/Alan_Turing" title="Alan Turing">Alan Turing</a> was a master of this on the early <a href="http://en.wikipedia.org/wiki/Manchester_Mark_1" title="Manchester Mark 1">Manchester Mark 1</a> machine, and he was already deriving the primitive conception of an operating system from the principles of the <a href="http://en.wikipedia.org/wiki/Universal_Turing_machine" title="Universal Turing machine">Universal Turing machine</a>.<sup class="Template-Fact" style="white-space: nowrap;">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources from June 2010">citation needed</span></a></i>]</sup><br />
Later machines came with libraries of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Computer_software" title="Computer software">software</a>, which would be linked to a user's program to assist in operations such as input and output and generating <a href="http://en.wikipedia.org/wiki/Machine_code" title="Machine code">computer code</a> from human-readable <a href="http://en.wikipedia.org/wiki/Assembly_language" title="Assembly language">symbolic code</a>.
This was the genesis of the modern-day operating system. However,
machines still ran a single job at a time. At Cambridge University in
England the job queue was at one time a washing line from which tapes
were hung with different colored clothes-pegs to indicate job-priority.<sup class="Template-Fact" style="white-space: nowrap;">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources from September 2010">citation needed</span></a></i>]</sup><br />
<h3>
<span class="editsection"></span> <span class="mw-headline" id="Mainframes">Mainframes</span></h3>
<div class="rellink boilerplate seealso">
See also: <a href="http://en.wikipedia.org/wiki/History_of_IBM_mainframe_operating_systems" title="History of IBM mainframe operating systems">History of IBM mainframe operating systems</a></div>
Through the 1950s, many major features were pioneered in the field of operating systems, including <a href="http://en.wikipedia.org/wiki/Batch_processing" title="Batch processing">batch processing</a>, input/output <a href="http://en.wikipedia.org/wiki/Interrupt" title="Interrupt">interrupt</a>, <a href="http://en.wikipedia.org/wiki/Data_buffer" title="Data buffer">buffering</a>, <a href="http://en.wikipedia.org/wiki/Computer_multitasking" title="Computer multitasking">multitasking</a>, <a href="http://en.wikipedia.org/wiki/Spooling" title="Spooling">spooling</a>, <a href="http://en.wikipedia.org/wiki/Runtime_library" title="Runtime library">runtime libraries</a>, <a href="http://en.wikipedia.org/wiki/Linker_%28computing%29" title="Linker (computing)">link-loading</a>, and programs for <a href="http://en.wikipedia.org/wiki/Sorting_algorithm" title="Sorting algorithm">sorting records</a>
in files. These features were included or not included in application
software at the option of application programmers, rather than in a
separate operating system used by all applications. In 1959 the <a href="http://en.wikipedia.org/wiki/SHARE_Operating_System" title="SHARE Operating System">SHARE Operating System</a> was released as an integrated utility for the <a href="http://en.wikipedia.org/wiki/IBM_704" title="IBM 704">IBM 704</a>, and later in the <a href="http://en.wikipedia.org/wiki/IBM_709" title="IBM 709">709</a> and <a href="http://en.wikipedia.org/wiki/IBM_7090" title="IBM 7090">7090</a> mainframes, although it was quickly supplanted by <a href="http://en.wikipedia.org/wiki/IBM_7090/94_IBSYS" title="IBM 7090/94 IBSYS">IBSYS</a>/IBJOB on the 709, 7090 and 7094.<br />
During the 1960s, IBM's <a class="mw-redirect" href="http://en.wikipedia.org/wiki/OS/360" title="OS/360">OS/360</a>
introduced the concept of a single OS spanning an entire product line,
which was crucial for the success of the System/360 machines. <a href="http://en.wikipedia.org/wiki/IBM" title="IBM">IBM</a>'s current mainframe operating systems are <a href="http://en.wikipedia.org/wiki/History_of_IBM_mainframe_operating_systems" title="History of IBM mainframe operating systems">distant descendants</a> of this original system and applications written for OS/360 can still be run on modern machines.<sup class="Template-Fact" style="white-space: nowrap;">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources from June 2010">citation needed</span></a></i>]</sup><br />
<a class="mw-redirect" href="http://en.wikipedia.org/wiki/OS/360" title="OS/360">OS/360</a>
also pioneered the concept that the operating system keeps track of all
of the system resources that are used, including program and data space
allocation in main memory and file space in secondary storage, and <a href="http://en.wikipedia.org/wiki/File_locking" title="File locking">file locking</a> during update. When the process is terminated for any reason, all of these resources are re-claimed by the operating system.<br />
The alternative <a href="http://en.wikipedia.org/wiki/CP-67" title="CP-67">CP-67</a> system for the <a href="http://en.wikipedia.org/wiki/IBM_System/360_Model_67" title="IBM System/360 Model 67">S/360-67</a> started a whole line of IBM operating systems focused on the concept of <a href="http://en.wikipedia.org/wiki/Virtual_machine" title="Virtual machine">virtual machines</a>.
Other operating systems used on IBM S/360 series mainframes included
systems developed by IBM: COS/360 (Compatabililty Operating System), <a class="mw-redirect" href="http://en.wikipedia.org/wiki/DOS/360" title="DOS/360">DOS/360</a> (Disk Operating System), <a href="http://en.wikipedia.org/wiki/TSS/360" title="TSS/360">TSS/360</a> (Time Sharing System), <a href="http://en.wikipedia.org/wiki/TOS/360" title="TOS/360">TOS/360</a> (Tape Operating System), <a href="http://en.wikipedia.org/wiki/BOS/360" title="BOS/360">BOS/360</a> (Basic Operating System), and <a href="http://en.wikipedia.org/wiki/IBM_Airline_Control_Program" title="IBM Airline Control Program">ACP</a> (Airline Control Program), as well as a few non-IBM systems: <a href="http://en.wikipedia.org/wiki/Michigan_Terminal_System" title="Michigan Terminal System">MTS</a> (Michigan Terminal System), <a href="http://en.wikipedia.org/wiki/MUSIC/SP" title="MUSIC/SP">MUSIC</a> (Multi-User System for Interactive Computing), and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/ORVYL" title="ORVYL">ORVYL</a> (Stanford Timesharing System).<br />
<a href="http://en.wikipedia.org/wiki/Control_Data_Corporation" title="Control Data Corporation">Control Data Corporation</a> developed the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/SCOPE_%28software%29" title="SCOPE (software)">SCOPE</a> operating system in the 1960s, for <a href="http://en.wikipedia.org/wiki/Batch_processing" title="Batch processing">batch processing</a>. In cooperation with the University of Minnesota, the <a href="http://en.wikipedia.org/wiki/CDC_Kronos" title="CDC Kronos">Kronos</a> and later the <a href="http://en.wikipedia.org/wiki/NOS_%28software%29" title="NOS (software)">NOS</a>
operating systems were developed during the 1970s, which supported
simultaneous batch and timesharing use. Like many commercial timesharing
systems, its interface was an extension of the Dartmouth BASIC
operating systems, one of the pioneering efforts in timesharing and
programming languages. In the late 1970s, Control Data and the
University of Illinois developed the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/PLATO" title="PLATO">PLATO</a>
operating system, which used plasma panel displays and long-distance
time sharing networks. Plato was remarkably innovative for its time,
featuring real-time chat, and multi-user graphical games. <a href="http://en.wikipedia.org/wiki/Burroughs_Corporation" title="Burroughs Corporation">Burroughs Corporation</a> introduced the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/B5000" title="B5000">B5000</a> in 1961 with the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Master_Control_Program" title="Master Control Program">MCP</a>, (<a class="mw-redirect" href="http://en.wikipedia.org/wiki/MCP_%28Burroughs_Large_Systems%29" title="MCP (Burroughs Large Systems)">Master Control Program</a>) operating system. The <a class="mw-redirect" href="http://en.wikipedia.org/wiki/B5000" title="B5000">B5000</a> was a <a href="http://en.wikipedia.org/wiki/Stack_machine" title="Stack machine">stack machine</a> designed to exclusively support high-level languages with no machine language or assembler, and indeed the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Master_Control_Program" title="Master Control Program">MCP</a> was the first OS to be written exclusively in a high-level language – <a href="http://en.wikipedia.org/wiki/ESPOL" title="ESPOL">ESPOL</a>, a dialect of <a href="http://en.wikipedia.org/wiki/ALGOL" title="ALGOL">ALGOL</a>. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Master_Control_Program" title="Master Control Program">MCP</a> also introduced many other ground-breaking innovations, such as being the first commercial implementation of <a href="http://en.wikipedia.org/wiki/Virtual_memory" title="Virtual memory">virtual memory</a>. During development of the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/AS400" title="AS400">AS400</a>, <a href="http://en.wikipedia.org/wiki/IBM" title="IBM">IBM</a>
made an approach to Burroughs to licence MCP to run on the AS400
hardware. This proposal was declined by Burroughs management to protect
its existing hardware production. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Master_Control_Program" title="Master Control Program">MCP</a> is still in use today in the <a href="http://en.wikipedia.org/wiki/Unisys" title="Unisys">Unisys</a> <a class="new" href="http://en.wikipedia.org/w/index.php?title=ClearPath/MCP&action=edit&redlink=1" title="ClearPath/MCP (page does not exist)">ClearPath/MCP</a> line of computers.<br />
UNIVAC, the first commercial computer manufacturer, produced a series
of EXEC operating systems. Like all early main-frame systems, this was a
batch-oriented system that managed magnetic drums, disks, card readers
and line printers. In the 1970s, UNIVAC produced the Real-Time Basic
(RTB) system to support large-scale time sharing, also patterned after
the Dartmouth BC system.<br />
General Electric and MIT developed General Electric Comprehensive
Operating Supervisor (GECOS), which introduced the concept of ringed
security privilege levels. After acquisition by Honeywell it was renamed
to <a href="http://en.wikipedia.org/wiki/General_Comprehensive_Operating_System" title="General Comprehensive Operating System">General Comprehensive Operating System</a> (GCOS).<br />
Digital Equipment Corporation developed many operating systems for its various computer lines, including <a href="http://en.wikipedia.org/wiki/TOPS-10" title="TOPS-10">TOPS-10</a> and <a href="http://en.wikipedia.org/wiki/TOPS-20" title="TOPS-20">TOPS-20</a>
time sharing systems for the 36-bit PDP-10 class systems. Prior to the
widespread use of UNIX, TOPS-10 was a particularly popular system in
universities, and in the early <a href="http://en.wikipedia.org/wiki/ARPANET" title="ARPANET">ARPANET</a> community.<br />
In the late 1960s through the late 1970s, several hardware
capabilities evolved that allowed similar or ported software to run on
more than one system. Early systems had utilized microprogramming to
implement features on their systems in order to permit different
underlying architecture to appear to be the same as others in a series.
In fact most 360s after the 360/40 (except the 360/165 and 360/168) were
microprogrammed implementations. But soon other means of achieving
application compatibility were proven to be more significant.<br />
The enormous investment in software for these systems made since
1960s caused most of the original computer manufacturers to continue to
develop compatible operating systems along with the hardware. The
notable supported mainframe operating systems include:<br />
<ul>
<li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/MCP_%28Burroughs_Large_Systems%29" title="MCP (Burroughs Large Systems)">Burroughs MCP</a> – <a href="http://en.wikipedia.org/wiki/Burroughs_large_systems" title="Burroughs large systems">B5000</a>, 1961 to <a href="http://en.wikipedia.org/wiki/Unisys" title="Unisys">Unisys</a> Clearpath/MCP, present.</li>
<li>IBM <a class="mw-redirect" href="http://en.wikipedia.org/wiki/OS/360" title="OS/360">OS/360</a> – <a href="http://en.wikipedia.org/wiki/IBM_System/360" title="IBM System/360">IBM System/360</a>, 1966 to IBM <a href="http://en.wikipedia.org/wiki/Z/OS" title="Z/OS">z/OS</a>, present.</li>
<li>IBM <a href="http://en.wikipedia.org/wiki/CP-67" title="CP-67">CP-67</a> – <a href="http://en.wikipedia.org/wiki/IBM_System/360" title="IBM System/360">IBM System/360</a>, 1967 to IBM <a href="http://en.wikipedia.org/wiki/Z/VM" title="Z/VM">z/VM</a>, present.</li>
<li>UNIVAC <a class="mw-redirect" href="http://en.wikipedia.org/wiki/EXEC_8" title="EXEC 8">EXEC 8</a> – <a class="mw-redirect" href="http://en.wikipedia.org/wiki/UNIVAC_1108" title="UNIVAC 1108">UNIVAC 1108</a>, 1967, to <a href="http://en.wikipedia.org/wiki/Unisys_OS_2200_operating_system" title="Unisys OS 2200 operating system">OS 2200</a> <a href="http://en.wikipedia.org/wiki/Unisys" title="Unisys">Unisys</a> Clearpath Dorado, present.</li>
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PC-DOS was an early personal computer OS that featured a command line interface.</div>
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Mac OS by <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Apple_Computer" title="Apple Computer">Apple Computer</a> became the first widespread OS to feature a <a href="http://en.wikipedia.org/wiki/Graphical_user_interface" title="Graphical user interface">graphical user interface</a>. Many of its features such as windows and icons would later become commonplace in GUIs.</div>
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The first <a href="http://en.wikipedia.org/wiki/Microcomputer" title="Microcomputer">microcomputers</a>
did not have the capacity or need for the elaborate operating systems
that had been developed for mainframes and minis; minimalistic operating
systems were developed, often loaded from <a href="http://en.wikipedia.org/wiki/Read-only_memory" title="Read-only memory">ROM</a> and known as <i>monitors</i>. One notable early disk-based operating system was <a href="http://en.wikipedia.org/wiki/CP/M" title="CP/M">CP/M</a>, which was supported on many early microcomputers and was closely imitated by <a href="http://en.wikipedia.org/wiki/Microsoft" title="Microsoft">Microsoft</a>'s <a href="http://en.wikipedia.org/wiki/MS-DOS" title="MS-DOS">MS-DOS</a>, which became wildly popular as the operating system chosen for the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/IBM_PC" title="IBM PC">IBM PC</a> (IBM's version of it was called IBM DOS or <a class="mw-redirect" href="http://en.wikipedia.org/wiki/PC-DOS" title="PC-DOS">PC DOS</a>). In the '80s, Apple Computer Inc. (now <a href="http://en.wikipedia.org/wiki/Apple_Inc." title="Apple Inc.">Apple Inc.</a>) abandoned its popular <a href="http://en.wikipedia.org/wiki/Apple_II" title="Apple II">Apple II</a> series of microcomputers to introduce the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Apple_Macintosh" title="Apple Macintosh">Apple Macintosh</a> computer with an innovative <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Graphical_User_Interface" title="Graphical User Interface">Graphical User Interface</a> (GUI) to the <a href="http://en.wikipedia.org/wiki/Mac_OS" title="Mac OS">Mac OS</a>.<br />
The introduction of the <a href="http://en.wikipedia.org/wiki/Intel_80386" title="Intel 80386">Intel 80386</a> <a class="mw-redirect" href="http://en.wikipedia.org/wiki/CPU" title="CPU">CPU</a> chip with <a href="http://en.wikipedia.org/wiki/32-bit" title="32-bit">32-bit</a> architecture and <a href="http://en.wikipedia.org/wiki/Paging" title="Paging">paging</a> capabilities, provided personal computers with the ability to run <a href="http://en.wikipedia.org/wiki/Computer_multitasking" title="Computer multitasking">multitasking</a> operating systems like those of earlier <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Minicomputers" title="Minicomputers">minicomputers</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Mainframes" title="Mainframes">mainframes</a>. Microsoft responded to this progress by hiring <a href="http://en.wikipedia.org/wiki/Dave_Cutler" title="Dave Cutler">Dave Cutler</a>, who had developed the <a href="http://en.wikipedia.org/wiki/OpenVMS" title="OpenVMS">VMS</a> operating system for <a href="http://en.wikipedia.org/wiki/Digital_Equipment_Corporation" title="Digital Equipment Corporation">Digital Equipment Corporation</a>. He would lead the development of the <a href="http://en.wikipedia.org/wiki/Windows_NT" title="Windows NT">Windows NT</a> operating system, which continues to serve as the basis for Microsoft's operating systems line. <a href="http://en.wikipedia.org/wiki/Steve_Jobs" title="Steve Jobs">Steve Jobs</a>, a co-founder of <a href="http://en.wikipedia.org/wiki/Apple_Inc." title="Apple Inc.">Apple Inc.</a>, started <a href="http://en.wikipedia.org/wiki/NeXT" title="NeXT">NeXT</a> Computer Inc., which developed the <a href="http://en.wikipedia.org/wiki/Unix-like" title="Unix-like">Unix-like</a> <a class="mw-redirect" href="http://en.wikipedia.org/wiki/NEXTSTEP" title="NEXTSTEP">NEXTSTEP</a> operating system. NEXTSTEP would later be acquired by <a href="http://en.wikipedia.org/wiki/Apple_Inc." title="Apple Inc.">Apple Inc.</a> and used, along with code from <a href="http://en.wikipedia.org/wiki/FreeBSD" title="FreeBSD">FreeBSD</a> as the core of Mac OS X.<br />
The <a href="http://en.wikipedia.org/wiki/GNU_Project" title="GNU Project">GNU Project</a> was started by activist and programmer <a href="http://en.wikipedia.org/wiki/Richard_Stallman" title="Richard Stallman">Richard Stallman</a> with the goal of a complete <a href="http://en.wikipedia.org/wiki/Free_software" title="Free software">free software</a> replacement to the proprietary <a class="mw-redirect" href="http://en.wikipedia.org/wiki/UNIX" title="UNIX">UNIX</a>
operating system. While the project was highly successful in
duplicating the functionality of various parts of UNIX, development of
the <a href="http://en.wikipedia.org/wiki/GNU_Hurd" title="GNU Hurd">GNU Hurd</a> kernel proved to be unproductive. In 1991, Finnish computer science student <a href="http://en.wikipedia.org/wiki/Linus_Torvalds" title="Linus Torvalds">Linus Torvalds</a>, with cooperation from volunteers collaborating over the Internet, released the first version of the <a href="http://en.wikipedia.org/wiki/Linux_kernel" title="Linux kernel">Linux kernel</a>. It was soon merged with the GNU <a href="http://en.wikipedia.org/wiki/User_space" title="User space">user space</a> components and <a href="http://en.wikipedia.org/wiki/System_software" title="System software">system software</a>
to form a complete operating system. Since then, the combination of the
two major components has usually been referred to as simply "Linux" by
the software industry, a naming convention that Stallman and the <a href="http://en.wikipedia.org/wiki/Free_Software_Foundation" title="Free Software Foundation">Free Software Foundation</a> remain opposed to, preferring the name GNU/Linux. The Berkeley Software Distribution, known as <a class="mw-redirect" href="http://en.wikipedia.org/wiki/BSD_%28operating_system%29" title="BSD (operating system)">BSD</a>, is the UNIX derivative distributed by the University of California, Berkeley, starting in the 1970s. Freely distributed and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Ported" title="Ported">ported</a> to many minicomputers, it eventually also gained a following for use on PCs, mainly as <a href="http://en.wikipedia.org/wiki/FreeBSD" title="FreeBSD">FreeBSD</a>, <a href="http://en.wikipedia.org/wiki/NetBSD" title="NetBSD">NetBSD</a> and <a href="http://en.wikipedia.org/wiki/OpenBSD" title="OpenBSD">OpenBSD</a>.<br />
<h2>
<span class="editsection"></span> <span class="mw-headline" id="Examples_of_operating_systems">Examples of operating systems</span></h2>
<h3>
<span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Operating_system&action=edit&section=7" title="Edit section: Unix and Unix-like operating systems">edit</a>]</span> <span class="mw-headline" id="Unix_and_Unix-like_operating_systems">Unix and Unix-like operating systems</span></h3>
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Evolution of <a href="http://en.wikipedia.org/wiki/Unix" title="Unix">Unix</a> systems</div>
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Main article: <a href="http://en.wikipedia.org/wiki/Unix" title="Unix">Unix</a></div>
<a href="http://en.wikipedia.org/wiki/Ken_Thompson" title="Ken Thompson">Ken Thompson</a> wrote <a href="http://en.wikipedia.org/wiki/B_%28programming_language%29" title="B (programming language)">B</a>, mainly based on <a href="http://en.wikipedia.org/wiki/BCPL" title="BCPL">BCPL</a>, which he used to write Unix, based on his experience in the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/MULTICS" title="MULTICS">MULTICS</a> project. B was replaced by <a href="http://en.wikipedia.org/wiki/C_%28programming_language%29" title="C (programming language)">C</a>,
and Unix developed into a large, complex family of inter-related
operating systems which have been influential in every modern operating
system (see <a href="http://en.wikipedia.org/wiki/History_of_operating_systems" title="History of operating systems">History</a>).<br />
The <i><a href="http://en.wikipedia.org/wiki/Unix-like" title="Unix-like">Unix-like</a></i> family is a diverse group of operating systems, with several major sub-categories including <a class="mw-redirect" href="http://en.wikipedia.org/wiki/System_V" title="System V">System V</a>, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/BSD_%28operating_system%29" title="BSD (operating system)">BSD</a>, and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/GNU/Linux" title="GNU/Linux">GNU/Linux</a>. The name "<a class="mw-redirect" href="http://en.wikipedia.org/wiki/UNIX" title="UNIX">UNIX</a>" is a trademark of <a href="http://en.wikipedia.org/wiki/The_Open_Group" title="The Open Group">The Open Group</a>
which licenses it for use with any operating system that has been shown
to conform to their definitions. "Unix-like" is commonly used to refer
to the large set of operating systems which resemble the original Unix.<br />
Unix-like systems run on a wide variety of machine architectures. They are used heavily for <a href="http://en.wikipedia.org/wiki/Server_%28computing%29" title="Server (computing)">servers</a> in business, as well as <a href="http://en.wikipedia.org/wiki/Workstation" title="Workstation">workstations</a> in academic and engineering environments. <a href="http://en.wikipedia.org/wiki/Free_software" title="Free software">Free</a> Unix variants, such as <a class="mw-redirect" href="http://en.wikipedia.org/wiki/GNU/Linux" title="GNU/Linux">GNU/Linux</a> and <a href="http://en.wikipedia.org/wiki/Berkeley_Software_Distribution" title="Berkeley Software Distribution">BSD</a>, are popular in these areas.<br />
Four operating systems are certified by the <a href="http://en.wikipedia.org/wiki/The_Open_Group" title="The Open Group">The Open Group</a> (holder of the Unix trademark) as Unix. HP's <a href="http://en.wikipedia.org/wiki/HP-UX" title="HP-UX">HP-UX</a> and IBM's <a class="mw-redirect" href="http://en.wikipedia.org/wiki/AIX_operating_system" title="AIX operating system">AIX</a>
are both descendants of the original System V Unix and are designed to
run only on their respective vendor's hardware. In contrast, <a href="http://en.wikipedia.org/wiki/Sun_Microsystems" title="Sun Microsystems">Sun Microsystems's</a> <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Solaris_Operating_System" title="Solaris Operating System">Solaris Operating System</a> can run on multiple types of hardware, including <a href="http://en.wikipedia.org/wiki/X86" title="X86">x86</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Sparc" title="Sparc">Sparc</a> servers, and PCs. Apple's <a href="http://en.wikipedia.org/wiki/Mac_OS_X" title="Mac OS X">Mac OS X</a>, a replacement for Apple's earlier (non-Unix) Mac OS, is a <a href="http://en.wikipedia.org/wiki/Hybrid_kernel" title="Hybrid kernel">hybrid kernel</a>-based BSD variant derived from <a href="http://en.wikipedia.org/wiki/NeXTSTEP" title="NeXTSTEP">NeXTSTEP</a>, <a href="http://en.wikipedia.org/wiki/Mach_%28kernel%29" title="Mach (kernel)">Mach</a>, and <a href="http://en.wikipedia.org/wiki/FreeBSD" title="FreeBSD">FreeBSD</a>.<br />
Unix interoperability was sought by establishing the <a href="http://en.wikipedia.org/wiki/POSIX" title="POSIX">POSIX</a>
standard. The POSIX standard can be applied to any operating system,
although it was originally created for various Unix variants.<br />
<h4>
<span class="editsection"></span> <span class="mw-headline" id="BSD_and_its_descendants">BSD and its descendants</span></h4>
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The <a href="http://en.wikipedia.org/wiki/CERN_httpd" title="CERN httpd">first server</a> for the <a href="http://en.wikipedia.org/wiki/World_Wide_Web" title="World Wide Web">World Wide Web</a> ran on NeXTSTEP, based on BSD.</div>
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Main article: <a href="http://en.wikipedia.org/wiki/Berkeley_Software_Distribution" title="Berkeley Software Distribution">Berkeley Software Distribution</a></div>
A subgroup of the Unix family is the <a href="http://en.wikipedia.org/wiki/Berkeley_Software_Distribution" title="Berkeley Software Distribution">Berkeley Software Distribution</a> family, which includes <a href="http://en.wikipedia.org/wiki/FreeBSD" title="FreeBSD">FreeBSD</a>, <a href="http://en.wikipedia.org/wiki/NetBSD" title="NetBSD">NetBSD</a>, and <a href="http://en.wikipedia.org/wiki/OpenBSD" title="OpenBSD">OpenBSD</a>. These operating systems are most commonly found on <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Webserver" title="Webserver">webservers</a>,
although they can also function as a personal computer OS. The Internet
owes much of its existence to BSD, as many of the protocols now
commonly used by computers to connect, send and receive data over a
network were widely implemented and refined in BSD. The <a class="mw-redirect" href="http://en.wikipedia.org/wiki/World_wide_web" title="World wide web">world wide web</a> was also first demonstrated on a number of computers running an OS based on BSD called <a class="mw-redirect" href="http://en.wikipedia.org/wiki/NextStep" title="NextStep">NextStep</a>.<br />
BSD has its roots in Unix. In 1974, <a href="http://en.wikipedia.org/wiki/University_of_California,_Berkeley" title="University of California, Berkeley">University of California, Berkeley</a>
installed its first Unix system. Over time, students and staff in the
computer science department there began adding new programs to make
things easier, such as text editors. When Berkely received new <a href="http://en.wikipedia.org/wiki/VAX" title="VAX">VAX</a>
computers in 1978 with Unix installed, the school's undergraduates
modified Unix even more in order to take advantage of the computer's
hardware possibilities. The <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Defense_Advanced_Research_Projects_Agency" title="Defense Advanced Research Projects Agency">Defense Advanced Research Projects Agency</a> of the US <a href="http://en.wikipedia.org/wiki/United_States_Department_of_Defense" title="United States Department of Defense">Department of Defense</a>
took interest, and decided to fund the project. Many schools,
corporations, and government organizations took notice and started to
use Berkeley's version of Unix instead of the official one distributed
by AT&T.<br />
<a href="http://en.wikipedia.org/wiki/Steve_Jobs" title="Steve Jobs">Steve Jobs</a>, upon leaving Apple Inc. in 1985, formed <a href="http://en.wikipedia.org/wiki/NeXT" title="NeXT">NeXT Inc.</a>, a company that manufactured high-end computers running on a variation of BSD called <a href="http://en.wikipedia.org/wiki/NeXTSTEP" title="NeXTSTEP">NeXTSTEP</a>. One of these computers was used by <a href="http://en.wikipedia.org/wiki/Tim_Berners-Lee" title="Tim Berners-Lee">Tim Berners-Lee</a> as the first webserver to create the World Wide Web.<br />
Developers like <a href="http://en.wikipedia.org/wiki/Keith_Bostic" title="Keith Bostic">Keith Bostic</a>
encouraged the project to replace any non-free code that originated
with Bell Labs. Once this was done, however, AT&T sued. Eventually,
after two years of legal disputes, the BSD project came out ahead and
spawned a number of free derivatives, such as <a href="http://en.wikipedia.org/wiki/FreeBSD" title="FreeBSD">FreeBSD</a> and <a href="http://en.wikipedia.org/wiki/NetBSD" title="NetBSD">NetBSD</a>.<br />
<h5>
<span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Operating_system&action=edit&section=9" title="Edit section: Mac OS X">edit</a>]</span> <span class="mw-headline" id="Mac_OS_X">Mac OS X</span></h5>
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The standard user interface of Mac OS X</div>
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Main article: <a href="http://en.wikipedia.org/wiki/Mac_OS_X" title="Mac OS X">Mac OS X</a></div>
Mac OS X is a line of <a href="http://en.wikipedia.org/wiki/Open_core" title="Open core">open core</a> graphical operating systems developed, marketed, and sold by <a href="http://en.wikipedia.org/wiki/Apple_Inc." title="Apple Inc.">Apple Inc.</a>, the latest of which is pre-loaded on all currently shipping <a href="http://en.wikipedia.org/wiki/Macintosh" title="Macintosh">Macintosh</a> computers. Mac OS X is the successor to the original <a href="http://en.wikipedia.org/wiki/Mac_OS" title="Mac OS">Mac OS</a>, which had been Apple's primary operating system since 1984. Unlike its predecessor, Mac OS X is a <a class="mw-redirect" href="http://en.wikipedia.org/wiki/UNIX" title="UNIX">UNIX</a> operating system built on technology that had been developed at <a href="http://en.wikipedia.org/wiki/NeXT" title="NeXT">NeXT</a> through the second half of the 1980s and up until Apple purchased the company in early 1997.<br />
The operating system was first released in 1999 as <a href="http://en.wikipedia.org/wiki/Mac_OS_X_Server_1.0" title="Mac OS X Server 1.0">Mac OS X Server 1.0</a>, with a desktop-oriented version (<a href="http://en.wikipedia.org/wiki/Mac_OS_X_v10.0" title="Mac OS X v10.0">Mac OS X v10.0 "Cheetah"</a>)
following in March 2001. Since then, six more distinct "client" and
"server" editions of Mac OS X have been released, the most recent being <a href="http://en.wikipedia.org/wiki/Mac_OS_X_Lion" title="Mac OS X Lion">Mac OS X 10.7 "Lion"</a>, which was first made available on July 20, 2011. Releases of Mac OS X are named after <a href="http://en.wikipedia.org/wiki/Big_cat" title="Big cat">big cats</a>; the current version of Mac OS X is "Lion".<br />
The server edition, <a href="http://en.wikipedia.org/wiki/Mac_OS_X_Server" title="Mac OS X Server">Mac OS X Server</a>, is <a href="http://en.wikipedia.org/wiki/Software_architecture" title="Software architecture">architecturally</a> identical to its desktop counterpart but usually runs on Apple's line of Macintosh <a href="http://en.wikipedia.org/wiki/Server_%28computing%29" title="Server (computing)">server</a>
hardware. Mac OS X Server includes work group management and
administration software tools that provide simplified access to key <a href="http://en.wikipedia.org/wiki/Network_service" title="Network service">network services</a>, including a <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Mail_transfer_agent" title="Mail transfer agent">mail transfer agent</a>, a <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Samba_software" title="Samba software">Samba server</a>, an <a class="mw-redirect" href="http://en.wikipedia.org/wiki/LDAP" title="LDAP">LDAP</a> server, a <a href="http://en.wikipedia.org/wiki/Domain_Name_System" title="Domain Name System">domain name server</a>, and others. In <a href="http://en.wikipedia.org/wiki/Mac_OS_X_Lion" title="Mac OS X Lion">Mac OS X v10.7 Lion</a>, all server aspects of Mac OS X Server have been integrated into the client version.<sup class="reference" id="cite_ref-4"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-4">[5]</a></sup><br />
<h4>
<span class="editsection"></span> <span class="mw-headline" id="Plan_9">Plan 9</span></h4>
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Main article: <a href="http://en.wikipedia.org/wiki/Plan_9_from_Bell_Labs" title="Plan 9 from Bell Labs">Plan 9 from Bell Labs</a></div>
<a href="http://en.wikipedia.org/wiki/Ken_Thompson" title="Ken Thompson">Ken Thompson</a>, <a href="http://en.wikipedia.org/wiki/Dennis_Ritchie" title="Dennis Ritchie">Dennis Ritchie</a> and <a href="http://en.wikipedia.org/wiki/Douglas_McIlroy" title="Douglas McIlroy">Douglas McIlroy</a> at <a href="http://en.wikipedia.org/wiki/Bell_Labs" title="Bell Labs">Bell Labs</a>
designed and developed the C programming language to build the
operating system Unix. Programmers at Bell Labs went on to develop <a href="http://en.wikipedia.org/wiki/Plan_9_from_Bell_Labs" title="Plan 9 from Bell Labs">Plan 9</a> and <a href="http://en.wikipedia.org/wiki/Inferno_%28operating_system%29" title="Inferno (operating system)">Inferno</a>,
which were engineered for modern distributed environments. Plan 9 was
designed from the start to be a networked operating system, and had
graphics built-in, unlike Unix, which added these features to the design
later. It is currently released under the <a href="http://en.wikipedia.org/wiki/Lucent_Public_License" title="Lucent Public License">Lucent Public License</a>. Inferno was sold to <a href="http://en.wikipedia.org/wiki/Vita_Nuova_Holdings" title="Vita Nuova Holdings">Vita Nuova Holdings</a> and has been released under a GPL/MIT license.<br />
<h4>
<span class="editsection"></span> <span class="mw-headline" id="Linux_and_GNU">Linux and GNU</span></h4>
<div class="rellink relarticle mainarticle">
Main articles: <a href="http://en.wikipedia.org/wiki/GNU" title="GNU">GNU</a>, <a href="http://en.wikipedia.org/wiki/Linux" title="Linux">Linux</a>, and <a href="http://en.wikipedia.org/wiki/Linux_kernel" title="Linux kernel">Linux kernel</a></div>
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<a href="http://en.wikipedia.org/wiki/Ubuntu_%28operating_system%29" title="Ubuntu (operating system)">Ubuntu</a>, desktop <a href="http://en.wikipedia.org/wiki/Linux_distribution" title="Linux distribution">Linux distribution</a></div>
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<a href="http://en.wikipedia.org/wiki/Android_%28operating_system%29" title="Android (operating system)">Android</a>, a popular mobile operating system using the Linux kernel</div>
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Linux (or <a class="mw-redirect" href="http://en.wikipedia.org/wiki/GNU/Linux" title="GNU/Linux">GNU/Linux</a>)
is a Unix-like operating system that was developed without any actual
Unix code, unlike BSD and its variants. Linux can be used on a wide
range of devices from supercomputers to wristwatches. The <a href="http://en.wikipedia.org/wiki/Linux_kernel" title="Linux kernel">Linux kernel</a>
is released under an open source license, so anyone can read and modify
its code. It has been modified to run on a large variety of
electronics. Although estimates suggest that Linux is used on 1.82% of
all personal computers,<sup class="reference" id="cite_ref-5"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-5">[6]</a></sup><sup class="reference" id="cite_ref-StatCounter_6-0"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-StatCounter-6">[7]</a></sup> it has been widely adopted for use in servers<sup class="reference" id="cite_ref-7"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-7">[8]</a></sup> and embedded systems<sup class="reference" id="cite_ref-8"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-8">[9]</a></sup> (such as cell phones). Linux has superseded Unix in most places<sup class="noprint Inline-Template" style="white-space: nowrap;">[<i><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Wikipedia:Avoid_weasel_words" title="Wikipedia:Avoid weasel words"><span title="The material in the vicinity of this tag may use weasel words or too-vague attribution. from July 2010">which?</span></a></i>]</sup>, and is used on the 10 most powerful supercomputers in the world.<sup class="reference" id="cite_ref-9"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-9">[10]</a></sup> The Linux kernel is used in some popular distributions, such as <a href="http://en.wikipedia.org/wiki/Red_Hat" title="Red Hat">Red Hat</a>, <a href="http://en.wikipedia.org/wiki/Debian" title="Debian">Debian</a>, <a href="http://en.wikipedia.org/wiki/Ubuntu_%28operating_system%29" title="Ubuntu (operating system)">Ubuntu</a>, <a href="http://en.wikipedia.org/wiki/Linux_Mint" title="Linux Mint">Linux Mint</a> and <a href="http://en.wikipedia.org/wiki/Google" title="Google">Google</a>'s <a href="http://en.wikipedia.org/wiki/Android_%28operating_system%29" title="Android (operating system)">Android</a>.<br />
The GNU project is a mass collaboration of programmers who seek to
create a completely free and open operating system that was similar to
Unix but with completely original code. It was started in 1983 by <a href="http://en.wikipedia.org/wiki/Richard_Stallman" title="Richard Stallman">Richard Stallman</a>,
and is responsible for many of the parts of most Linux variants. For
this reason, some claim that the combined product of the Linux kernel
and the GNU software collection is more correctly called <a class="mw-redirect" href="http://en.wikipedia.org/wiki/GNU/Linux" title="GNU/Linux">GNU/Linux</a>. Thousands of pieces of software for virtually every operating system are licensed under the <a href="http://en.wikipedia.org/wiki/GNU_General_Public_License" title="GNU General Public License">GNU General Public License</a>. Meanwhile, the Linux kernel began as a side project of <a href="http://en.wikipedia.org/wiki/Linus_Torvalds" title="Linus Torvalds">Linus Torvalds</a>,
a university student from Finland. In 1991, Torvalds began work on it,
and posted information about his project on a newsgroup for computer
students and programmers. He received a wave of support and volunteers
who ended up creating a full-fledged kernel. Programmers from GNU took
notice, and members of both projects worked to integrate the finished
GNU parts with the Linux kernel in order to create a full-fledged
operating system.<br />
<h5>
<span class="editsection"></span> <span class="mw-headline" id="Google_Chrome_OS">Google Chrome OS</span></h5>
<div class="rellink relarticle mainarticle">
Main article: <a href="http://en.wikipedia.org/wiki/Google_Chrome_OS" title="Google Chrome OS">Google Chrome OS</a></div>
Chrome is an operating system based on the Linux kernel and designed by <a href="http://en.wikipedia.org/wiki/Google" title="Google">Google</a>. Since Chrome OS targets computer users who spend most of their time on the Internet, it is mainly a <a href="http://en.wikipedia.org/wiki/Web_browser" title="Web browser">web browser</a> with no ability to run applications. It relies on <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Internet_application" title="Internet application">Internet applications</a> (or <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Web_app" title="Web app">Web apps</a>) used in the web browser to accomplish tasks such as word processing and media viewing, as well as <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Online_storage" title="Online storage">online storage</a> for storing most files.<br />
<h3>
<span class="editsection"></span> <span class="mw-headline" id="AmigaOS">AmigaOS</span></h3>
<div class="rellink relarticle mainarticle">
Main article: <a href="http://en.wikipedia.org/wiki/AmigaOS" title="AmigaOS">AmigaOS</a></div>
AmigaOS is the default native operating system of the <a href="http://en.wikipedia.org/wiki/Amiga" title="Amiga">Amiga</a> personal computer. It was developed first by the <a href="http://en.wikipedia.org/wiki/Amiga_Corporation" title="Amiga Corporation">Amiga Corporation</a> then sold to <a href="http://en.wikipedia.org/wiki/Commodore_International" title="Commodore International">Commodore International</a>, and initially introduced in 1985 with the <a href="http://en.wikipedia.org/wiki/Amiga_1000" title="Amiga 1000">Amiga 1000</a>.
Early versions (1.0-3.9) run on the Motorola 68k series of 16-bit and
32-bit microprocessors, while the newer AmigaOS 4 runs only on PowerPC
microprocessors. On top of a preemptive multitasking kernel called Exec,
it includes an abstraction of the Amiga's unique hardware, a disk
operating system called AmigaDOS, a windowing system API called
Intuition and a graphical user interface called Workbench. A command
line interface called AmigaShell is also available and integrated into
the system. The GUI and the CLI complement each other and share the same
privileges. The current holder of the Amiga intellectual properties is <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Amiga_Inc" title="Amiga Inc">Amiga Inc</a>. They oversaw the development of <a href="http://en.wikipedia.org/wiki/AmigaOS_4" title="AmigaOS 4">AmigaOS 4</a>
but did not develop it themselves, contracting it instead to Hyperion
Entertainment. On 20 December 2006, Amiga Inc terminated Hyperion's
license to continue development of <a href="http://en.wikipedia.org/wiki/AmigaOS_4" title="AmigaOS 4">AmigaOS 4</a>. However, in 30 September 2009, Hyperion was granted an exclusive, perpetual, worldwide right to <a class="new" href="http://en.wikipedia.org/w/index.php?title=AmigaOS_3.1&action=edit&redlink=1" title="AmigaOS 3.1 (page does not exist)">AmigaOS 3.1</a>
in order to use, develop, modify, commercialize, distribute and market
AmigaOS 4.x and subsequent versions of AmigaOS (including AmigaOS 5).<sup class="reference" id="cite_ref-10"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-10">[11]</a></sup><br />
<h3>
<span class="editsection"></span> <span class="mw-headline" id="Microsoft_Windows">Microsoft Windows</span></h3>
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Main article: <a href="http://en.wikipedia.org/wiki/Microsoft_Windows" title="Microsoft Windows">Microsoft Windows</a></div>
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Bootable <a href="http://en.wikipedia.org/wiki/Windows_To_Go" title="Windows To Go">Windows To Go</a> USB flash drive</div>
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Microsoft Windows is a family of <a href="http://en.wikipedia.org/wiki/Proprietary_software" title="Proprietary software">proprietary</a> operating systems designed by <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Microsoft_Corporation" title="Microsoft Corporation">Microsoft Corporation</a>
and primarily targeted to Intel architecture based computers, with an
estimated 88.9 percent total usage share on Web connected computers.<sup class="reference" id="cite_ref-StatCounter_6-1"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-StatCounter-6">[7]</a></sup><sup class="reference" id="cite_ref-11"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-11">[12]</a></sup><sup class="reference" id="cite_ref-w3cstats_12-0"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-w3cstats-12">[13]</a></sup><sup class="reference" id="cite_ref-13"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-13">[14]</a></sup> The newest version is <a href="http://en.wikipedia.org/wiki/Windows_7" title="Windows 7">Windows 7</a> for workstations and <a href="http://en.wikipedia.org/wiki/Windows_Server_2008_R2" title="Windows Server 2008 R2">Windows Server 2008 R2</a> for servers. Windows 7 recently overtook Windows XP as most used OS.<sup class="reference" id="cite_ref-w3schoolsOSStats_14-0"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-w3schoolsOSStats-14">[15]</a></sup><sup class="reference" id="cite_ref-gstats2011_15-0"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-gstats2011-15">[16]</a></sup><sup class="reference" id="cite_ref-globstats_16-0"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-globstats-16">[17]</a></sup><br />
Microsoft Windows originated in 1985 as an application running on top of <a href="http://en.wikipedia.org/wiki/MS-DOS" title="MS-DOS">MS-DOS</a>, which was the standard operating system shipped on most Intel architecture personal computers at the time. In 1995, <a href="http://en.wikipedia.org/wiki/Windows_95" title="Windows 95">Windows 95</a>
was released, combining MS-DOS 7.0 with Windows on the same medium,
removing the need of getting a separate MS-DOS license. Keeping much
legacy, it could run real-mode MS-DOS<sup class="reference" id="cite_ref-17"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-17">[18]</a></sup><sup class="reference" id="cite_ref-18"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-18">[19]</a></sup> and 16 bits Windows 3.x<sup class="reference" id="cite_ref-19"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-19">[20]</a></sup> drivers. <a href="http://en.wikipedia.org/wiki/Windows_Me" title="Windows Me">Windows Me</a>, released in 2000, was the latest version of Windows of the Windows 95 family. Later versions have all been based on the <a href="http://en.wikipedia.org/wiki/Windows_NT" title="Windows NT">Windows NT</a> <a href="http://en.wikipedia.org/wiki/Kernel_%28computing%29" title="Kernel (computing)">kernel</a>. Current versions of Windows run on <a href="http://en.wikipedia.org/wiki/IA-32" title="IA-32">IA-32</a> and <a href="http://en.wikipedia.org/wiki/X86-64" title="X86-64">x86-64</a> <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Microprocessors" title="Microprocessors">microprocessors</a>, although Windows 8 will support ARM architecture. In the past, Windows NT supported a few non-Intel architectures.<br />
Server editions of Windows are widely used. In recent years,
Microsoft has expended significant capital in an effort to promote the
use of Windows as a server operating environment. However, Windows'
usage on servers is not as widespread as on personal computers, as
Windows competes against Linux and BSD for server market share.<sup class="reference" id="cite_ref-20"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-20">[21]</a></sup><sup class="reference" id="cite_ref-21"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-21">[22]</a></sup><br />
<h3>
<span class="editsection"></span> <span class="mw-headline" id="Other">Other</span></h3>
Older operating systems which are still used in niche markets include <a href="http://en.wikipedia.org/wiki/OS/2" title="OS/2">OS/2</a> from IBM and Microsoft; <a href="http://en.wikipedia.org/wiki/Mac_OS" title="Mac OS">Mac OS</a>, the non-Unix precursor to Apple's Mac OS X; <a href="http://en.wikipedia.org/wiki/BeOS" title="BeOS">BeOS</a>; <a href="http://en.wikipedia.org/wiki/XTS-400" title="XTS-400">XTS-300</a>. Some, most notably <a href="http://en.wikipedia.org/wiki/Haiku_%28operating_system%29" title="Haiku (operating system)">Haiku</a>, <a href="http://en.wikipedia.org/wiki/RISC_OS" title="RISC OS">RISC OS</a>, <a href="http://en.wikipedia.org/wiki/MorphOS" title="MorphOS">MorphOS</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/FreeMint" title="FreeMint">FreeMint</a> continue to be developed as minority platforms for enthusiast communities and specialist applications. <a href="http://en.wikipedia.org/wiki/OpenVMS" title="OpenVMS">OpenVMS</a> formerly from <a href="http://en.wikipedia.org/wiki/Digital_Equipment_Corporation" title="Digital Equipment Corporation">DEC</a>, is still under active development by <a href="http://en.wikipedia.org/wiki/Hewlett-Packard" title="Hewlett-Packard">Hewlett-Packard</a>.
Yet other operating systems are used almost exclusively in academia,
for operating systems education or to do research on operating system
concepts. A typical example of a system that fulfills both roles is <a href="http://en.wikipedia.org/wiki/MINIX" title="MINIX">MINIX</a>, while for example <a href="http://en.wikipedia.org/wiki/Singularity_%28operating_system%29" title="Singularity (operating system)">Singularity</a> is used purely for research.<br />
<h2>
<span class="editsection"></span> <span class="mw-headline" id="Components">Components</span></h2>
The components of an operating system all exist in order to make the
different parts of a computer work together. All software—from financial
databases to film editors—needs to go through the operating system in
order to use any of the hardware, whether it be as simple as a mouse or
keyboard or complex as an Internet connection.<br />
<h3>
<span class="editsection"></span> <span class="mw-headline" id="Kernel">Kernel</span></h3>
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A kernel connects the application software to the hardware of a computer.</div>
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<div class="rellink relarticle mainarticle">
Main article: <a href="http://en.wikipedia.org/wiki/Kernel_%28computing%29" title="Kernel (computing)">Kernel (computing)</a></div>
With the aid of the <a href="http://en.wikipedia.org/wiki/Firmware" title="Firmware">firmware</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Device_drivers" title="Device drivers">device drivers</a>,
the kernel provides the most basic level of control over all of the
computer's hardware devices. It manages memory access for programs in
the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/RAM" title="RAM">RAM</a>,
it determines which programs get access to which hardware resources, it
sets up or resets the CPU's operating states for optimal operation at
all times, and it organizes the data for long-term <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Non-volatile_storage" title="Non-volatile storage">non-volatile storage</a> with <a class="mw-redirect" href="http://en.wikipedia.org/wiki/File_systems" title="File systems">file systems</a> on such media as disks, tapes, flash memory, etc.<br />
<h4>
<span class="editsection"></span> <span class="mw-headline" id="Program_execution">Program execution</span></h4>
<div class="rellink relarticle mainarticle">
Main article: <a href="http://en.wikipedia.org/wiki/Process_%28computing%29" title="Process (computing)">Process (computing)</a></div>
The operating system provides an interface between an application
program and the computer hardware, so that an application program can
interact with the hardware only by obeying rules and procedures
programmed into the operating system. The operating system is also a set
of services which simplify development and execution of application
programs. Executing an application program involves the creation of a
process by the operating system <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Kernel_%28computer_science%29" title="Kernel (computer science)">kernel</a>
which assigns memory space and other resources, establishes a priority
for the process in multi-tasking systems, loads program binary code into
memory, and initiates execution of the application program which then
interacts with the user and with hardware devices.<br />
<h4>
<span class="editsection"></span> <span class="mw-headline" id="Interrupts">Interrupts</span></h4>
<div class="rellink relarticle mainarticle">
Main article: <a href="http://en.wikipedia.org/wiki/Interrupt" title="Interrupt">Interrupt</a></div>
<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Interrupts" title="Interrupts">Interrupts</a>
are central to operating systems, as they provide an efficient way for
the operating system to interact with and react to its environment. The
alternative — having the operating system "watch" the various sources of
input for events (polling) that require action — can be found in older
systems with very small <a href="http://en.wikipedia.org/wiki/Call_stack" title="Call stack">stacks</a> (50 or 60 bytes) but are unusual in modern systems with large stacks. <a href="http://en.wikipedia.org/wiki/Interrupt" title="Interrupt">Interrupt</a>-based
programming is directly supported by most modern CPUs. Interrupts
provide a computer with a way of automatically saving local register
contexts, and running specific code in response to events. Even very
basic computers support hardware interrupts, and allow the programmer to
specify code which may be run when that event takes place.<br />
When an interrupt is received, the computer's hardware automatically
suspends whatever program is currently running, saves its status, and
runs computer code previously associated with the interrupt; this is
analogous to placing a bookmark in a book in response to a phone call.
In modern operating systems, interrupts are handled by the operating
system's <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Kernel_%28computer_science%29" title="Kernel (computer science)">kernel</a>. Interrupts may come from either the computer's hardware or from the running program.<br />
When a hardware device triggers an interrupt, the operating system's
kernel decides how to deal with this event, generally by running some
processing code. The amount of code being run depends on the priority of
the interrupt (for example: a person usually responds to a smoke
detector alarm before answering the phone). The processing of hardware
interrupts is a task that is usually delegated to software called <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Device_drivers" title="Device drivers">device driver</a>,
which may be either part of the operating system's kernel, part of
another program, or both. Device drivers may then relay information to a
running program by various means.<br />
A program may also trigger an interrupt to the operating system. If a
program wishes to access hardware for example, it may interrupt the
operating system's kernel, which causes control to be passed back to the
kernel. The kernel will then process the request. If a program wishes
additional resources (or wishes to shed resources) such as memory, it
will trigger an interrupt to get the kernel's attention.<br />
<h4>
<span class="editsection"></span> <span class="mw-headline" id="Modes">Modes</span></h4>
<div class="rellink relarticle mainarticle">
Main articles: <a href="http://en.wikipedia.org/wiki/Protected_mode" title="Protected mode">Protected mode</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Supervisor_mode" title="Supervisor mode">Supervisor mode</a></div>
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Privilege rings for the <a href="http://en.wikipedia.org/wiki/X86" title="X86">x86</a> available in <a href="http://en.wikipedia.org/wiki/Protected_mode" title="Protected mode">protected mode</a>. Operating systems determine which processes run in each mode.</div>
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Modern CPUs support multiple modes of operation. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/CPU" title="CPU">CPUs</a> with this capability use at least two modes: <a href="http://en.wikipedia.org/wiki/Protected_mode" title="Protected mode">protected mode</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Supervisor_mode" title="Supervisor mode">supervisor mode</a>.
The supervisor mode is used by the operating system's kernel for low
level tasks that need unrestricted access to hardware, such as
controlling how memory is written and erased, and communication with
devices like graphics cards. Protected mode, in contrast, is used for
almost everything else. Applications operate within protected mode, and
can only use hardware by communicating with the kernel, which controls
everything in supervisor mode. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/CPU" title="CPU">CPUs</a>
might have other modes similar to protected mode as well, such as the
virtual modes in order to emulate older processor types, such as 16-bit
processors on a 32-bit one, or 32-bit processors on a 64-bit one.<br />
When a computer first starts up, it is automatically running in <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Supervisor_mode" title="Supervisor mode">supervisor mode</a>. The first few programs to run on the computer, being the <a href="http://en.wikipedia.org/wiki/BIOS" title="BIOS">BIOS</a> or <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Extensible_Firmware_Interface" title="Extensible Firmware Interface">EFI</a>, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Bootloader" title="Bootloader">bootloader</a>,
and the operating system have unlimited access to hardware - and this
is required because, by definition, initializing a protected environment
can only be done outside of one. However, when the operating system
passes control to another program, it can place the CPU into <a href="http://en.wikipedia.org/wiki/Protected_mode" title="Protected mode">protected mode</a>.<br />
In <a href="http://en.wikipedia.org/wiki/Protected_mode" title="Protected mode">protected mode</a>, programs may have access to a more limited set of the CPU's instructions. A user program may leave <a href="http://en.wikipedia.org/wiki/Protected_mode" title="Protected mode">protected mode</a> only by triggering an interrupt, causing control to be passed back to the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Kernel_%28computer_science%29" title="Kernel (computer science)">kernel</a>. In this way the operating system can maintain exclusive control over things like access to hardware and memory.<br />
The term "protected mode resource" generally refers to one or more
CPU registers, which contain information that the running program isn't
allowed to alter. Attempts to alter these resources generally causes a
switch to supervisor mode, where the operating system can deal with the
illegal operation the program was attempting (for example, by killing
the program).<br />
<h4>
<span class="editsection"></span> <span class="mw-headline" id="Memory_management">Memory management</span></h4>
<div class="rellink relarticle mainarticle">
Main article: <a href="http://en.wikipedia.org/wiki/Memory_management" title="Memory management">Memory management</a></div>
Among other things, a multiprogramming operating system <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Kernel_%28computer_science%29" title="Kernel (computer science)">kernel</a>
must be responsible for managing all system memory which is currently
in use by programs. This ensures that a program does not interfere with
memory already in use by another program. Since programs time share,
each program must have independent access to memory.<br />
Cooperative memory management, used by many early operating systems, assumes that all programs make voluntary use of the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Kernel_%28computer_science%29" title="Kernel (computer science)">kernel</a>'s
memory manager, and do not exceed their allocated memory. This system
of memory management is almost never seen any more, since programs often
contain bugs which can cause them to exceed their allocated memory. If a
program fails, it may cause memory used by one or more other programs
to be affected or overwritten. Malicious programs or viruses may
purposefully alter another program's memory, or may affect the operation
of the operating system itself. With cooperative memory management, it
takes only one misbehaved program to crash the system.<br />
<a href="http://en.wikipedia.org/wiki/Memory_protection" title="Memory protection">Memory protection</a> enables the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Kernel_%28computer_science%29" title="Kernel (computer science)">kernel</a> to limit a process' access to the computer's memory. Various methods of memory protection exist, including <a href="http://en.wikipedia.org/wiki/Memory_segmentation" title="Memory segmentation">memory segmentation</a> and <a href="http://en.wikipedia.org/wiki/Paging" title="Paging">paging</a>. All methods require some level of hardware support (such as the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/80286" title="80286">80286</a> MMU), which doesn't exist in all computers.<br />
In both segmentation and paging, certain <a href="http://en.wikipedia.org/wiki/Protected_mode" title="Protected mode">protected mode</a>
registers specify to the CPU what memory address it should allow a
running program to access. Attempts to access other addresses will
trigger an interrupt which will cause the CPU to re-enter <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Supervisor_mode" title="Supervisor mode">supervisor mode</a>, placing the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Kernel_%28computer_science%29" title="Kernel (computer science)">kernel</a> in charge. This is called a <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Segmentation_violation" title="Segmentation violation">segmentation violation</a>
or Seg-V for short, and since it is both difficult to assign a
meaningful result to such an operation, and because it is usually a sign
of a misbehaving program, the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Kernel_%28computer_science%29" title="Kernel (computer science)">kernel</a> will generally resort to terminating the offending program, and will report the error.<br />
Windows 3.1-Me had some level of memory protection, but programs could easily circumvent the need to use it. A <a href="http://en.wikipedia.org/wiki/General_protection_fault" title="General protection fault">general protection fault</a> would be produced, indicating a segmentation violation had occurred; however, the system would often crash anyway.<br />
<h4>
<span class="editsection"></span> <span class="mw-headline" id="Virtual_memory">Virtual memory</span></h4>
<div class="rellink relarticle mainarticle">
Main article: <a href="http://en.wikipedia.org/wiki/Virtual_memory" title="Virtual memory">Virtual memory</a></div>
<div class="rellink">
Further information: <a href="http://en.wikipedia.org/wiki/Page_fault" title="Page fault">Page fault</a></div>
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Many operating systems can "trick" programs into using memory scattered
around the hard disk and RAM as if it is one continuous chunk of memory,
called virtual memory.</div>
</div>
</div>
The use of virtual memory addressing (such as paging or segmentation)
means that the kernel can choose what memory each program may use at
any given time, allowing the operating system to use the same memory
locations for multiple tasks.<br />
If a program tries to access memory that isn't in its current range
of accessible memory, but nonetheless has been allocated to it, the
kernel will be interrupted in the same way as it would if the program
were to exceed its allocated memory. (See section on memory management.)
Under UNIX this kind of interrupt is referred to as a <a href="http://en.wikipedia.org/wiki/Page_fault" title="Page fault">page fault</a>.<br />
When the kernel detects a page fault it will generally adjust the
virtual memory range of the program which triggered it, granting it
access to the memory requested. This gives the kernel discretionary
power over where a particular application's memory is stored, or even
whether or not it has actually been allocated yet.<br />
In modern operating systems, memory which is accessed less frequently
can be temporarily stored on disk or other media to make that space
available for use by other programs. This is called <a href="http://en.wikipedia.org/wiki/Paging" title="Paging">swapping</a>,
as an area of memory can be used by multiple programs, and what that
memory area contains can be swapped or exchanged on demand.<br />
"Virtual memory" provides the programmer or the user with the
perception that there is a much larger amount of RAM in the computer
than is really there.<sup class="reference" id="cite_ref-Operating_System_22-0"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-Operating_System-22"></a></sup><br />
<h4>
<span class="editsection"></span> <span class="mw-headline" id="Multitasking">Multitasking</span></h4>
<div class="rellink relarticle mainarticle">
Main articles: <a href="http://en.wikipedia.org/wiki/Computer_multitasking" title="Computer multitasking">Computer multitasking</a> and <a href="http://en.wikipedia.org/wiki/Process_management_%28computing%29" title="Process management (computing)">Process management (computing)</a></div>
<div class="rellink">
Further information: <a href="http://en.wikipedia.org/wiki/Context_switch" title="Context switch">Context switch</a>, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Preemptive_multitasking" title="Preemptive multitasking">Preemptive multitasking</a>, and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Cooperative_multitasking" title="Cooperative multitasking">Cooperative multitasking</a></div>
<a href="http://en.wikipedia.org/wiki/Computer_multitasking" title="Computer multitasking">Multitasking</a>
refers to the running of multiple independent computer programs on the
same computer; giving the appearance that it is performing the tasks at
the same time. Since most computers can do at most one or two things at
one time, this is generally done via time-sharing, which means that each
program uses a share of the computer's time to execute.<br />
An operating system <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Kernel_%28computer_science%29" title="Kernel (computer science)">kernel</a> contains a piece of software called a <a href="http://en.wikipedia.org/wiki/Scheduling_%28computing%29" title="Scheduling (computing)">scheduler</a>
which determines how much time each program will spend executing, and
in which order execution control should be passed to programs. Control
is passed to a process by the kernel, which allows the program access to
the <a href="http://en.wikipedia.org/wiki/Central_processing_unit" title="Central processing unit">CPU</a>
and memory. Later, control is returned to the kernel through some
mechanism, so that another program may be allowed to use the CPU. This
so-called passing of control between the kernel and applications is
called a <a href="http://en.wikipedia.org/wiki/Context_switch" title="Context switch">context switch</a>.<br />
An early model which governed the allocation of time to programs was called <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Cooperative_multitasking" title="Cooperative multitasking">cooperative multitasking</a>.
In this model, when control is passed to a program by the kernel, it
may execute for as long as it wants before explicitly returning control
to the kernel. This means that a malicious or malfunctioning program may
not only prevent any other programs from using the CPU, but it can hang
the entire system if it enters an <a href="http://en.wikipedia.org/wiki/Infinite_loop" title="Infinite loop">infinite loop</a>.<br />
Modern operating systems extend the concepts of application
preemption to device drivers and kernel code, so that the operating
system has preemptive control over internal run-times as well.<br />
The philosophy governing <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Preemptive_multitasking" title="Preemptive multitasking">preemptive multitasking</a>
is that of ensuring that all programs are given regular time on the
CPU. This implies that all programs must be limited in how much time
they are allowed to spend on the CPU without being interrupted. To
accomplish this, modern operating system kernels make use of a timed
interrupt. A <a href="http://en.wikipedia.org/wiki/Protected_mode" title="Protected mode">protected mode</a>
timer is set by the kernel which triggers a return to supervisor mode
after the specified time has elapsed. (See above sections on Interrupts
and Dual Mode Operation.)<br />
On many single user operating systems cooperative multitasking is
perfectly adequate, as home computers generally run a small number of
well tested programs. The <a href="http://en.wikipedia.org/wiki/AmigaOS" title="AmigaOS">AmigaOS</a> is an exception, having pre-emptive multitasking from its very first version. <a href="http://en.wikipedia.org/wiki/Windows_NT" title="Windows NT">Windows NT</a> was the first version of <a href="http://en.wikipedia.org/wiki/Microsoft_Windows" title="Microsoft Windows">Microsoft Windows</a> which enforced preemptive multitasking, but it didn't reach the home user market until <a href="http://en.wikipedia.org/wiki/Windows_XP" title="Windows XP">Windows XP</a> (since <a href="http://en.wikipedia.org/wiki/Windows_NT" title="Windows NT">Windows NT</a> was targeted at professionals).<br />
<h4>
<span class="editsection"></span> <span class="mw-headline" id="Disk_access_and_file_systems">Disk access and file systems</span></h4>
<div class="rellink relarticle mainarticle">
Main article: <a href="http://en.wikipedia.org/wiki/Virtual_file_system" title="Virtual file system">Virtual file system</a></div>
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Filesystems allow users and programs to organize and sort files on a
computer, often through the use of directories (or "folders")</div>
</div>
</div>
Access to data stored on disks is a central feature of all operating systems. Computers store data on <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Hard_disk_drives" title="Hard disk drives">disks</a> using <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Computer_files" title="Computer files">files</a>,
which are structured in specific ways in order to allow for faster
access, higher reliability, and to make better use out of the drive's
available space. The specific way in which files are stored on a disk is
called a <a href="http://en.wikipedia.org/wiki/File_system" title="File system">file system</a>,
and enables files to have names and attributes. It also allows them to
be stored in a hierarchy of directories or folders arranged in a <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Directory_tree" title="Directory tree">directory tree</a>.<br />
Early operating systems generally supported a single type of disk
drive and only one kind of file system. Early file systems were limited
in their capacity, speed, and in the kinds of file names and directory
structures they could use. These limitations often reflected limitations
in the operating systems they were designed for, making it very
difficult for an operating system to support more than one file system.<br />
While many simpler operating systems support a limited range of options for accessing storage systems, operating systems like <a class="mw-redirect" href="http://en.wikipedia.org/wiki/UNIX" title="UNIX">UNIX</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/GNU/Linux" title="GNU/Linux">GNU/Linux</a> support a technology known as a <a href="http://en.wikipedia.org/wiki/Virtual_file_system" title="Virtual file system">virtual file system</a> or VFS. An operating system such as UNIX supports a wide array of storage devices, regardless of their design or <a href="http://en.wikipedia.org/wiki/File_system" title="File system">file systems</a>, allowing them to be accessed through a common <a href="http://en.wikipedia.org/wiki/Application_programming_interface" title="Application programming interface">application programming interface</a>
(API). This makes it unnecessary for programs to have any knowledge
about the device they are accessing. A VFS allows the operating system
to provide programs with access to an unlimited number of devices with
an infinite variety of file systems installed on them, through the use
of specific <a href="http://en.wikipedia.org/wiki/Device_driver" title="Device driver">device drivers</a> and file system drivers.<br />
A connected <a href="http://en.wikipedia.org/wiki/Data_storage_device" title="Data storage device">storage device</a>, such as a <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Hard_drive" title="Hard drive">hard drive</a>, is accessed through a <a href="http://en.wikipedia.org/wiki/Device_driver" title="Device driver">device driver</a>.
The device driver understands the specific language of the drive and is
able to translate that language into a standard language used by the
operating system to access all disk drives. On UNIX, this is the
language of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Block_devices" title="Block devices">block devices</a>.<br />
When the kernel has an appropriate device driver in place, it can
then access the contents of the disk drive in raw format, which may
contain one or more file systems. A file system driver is used to
translate the commands used to access each specific file system into a
standard set of commands that the operating system can use to talk to
all file systems. Programs can then deal with these file systems on the
basis of filenames, and directories/folders, contained within a
hierarchical structure. They can create, delete, open, and close files,
as well as gather various information about them, including access
permissions, size, free space, and creation and modification dates.<br />
Various differences between file systems make supporting all file systems difficult. Allowed characters in file names, <a href="http://en.wikipedia.org/wiki/Case_sensitivity" title="Case sensitivity">case sensitivity</a>, and the presence of various kinds of <a href="http://en.wikipedia.org/wiki/File_attribute" title="File attribute">file attributes</a>
makes the implementation of a single interface for every file system a
daunting task. Operating systems tend to recommend using (and so support
natively) file systems specifically designed for them; for example, <a href="http://en.wikipedia.org/wiki/NTFS" title="NTFS">NTFS</a> in Windows and <a href="http://en.wikipedia.org/wiki/Ext3" title="Ext3">ext3</a> and <a href="http://en.wikipedia.org/wiki/ReiserFS" title="ReiserFS">ReiserFS</a>
in GNU/Linux. However, in practice, third party drives are usually
available to give support for the most widely used file systems in most
general-purpose operating systems (for example, NTFS is available in
GNU/Linux through <a class="mw-redirect" href="http://en.wikipedia.org/wiki/NTFS-3g" title="NTFS-3g">NTFS-3g</a>, and ext2/3 and ReiserFS are available in Windows through <a class="external text" href="http://www.fs-driver.org/" rel="nofollow">FS-driver</a> and <a class="external text" href="http://p-nand-q.com/download/rfstool.html" rel="nofollow">rfstool</a>).<br />
Support for file systems is highly varied among modern operating
systems, although there are several common file systems which almost all
operating systems include support and drivers for. Operating systems
vary on file system support and on the disk formats they may be
installed on. Under Windows, each file system is usually limited in
application to certain media; for example, CDs must use <a href="http://en.wikipedia.org/wiki/ISO_9660" title="ISO 9660">ISO 9660</a> or <a href="http://en.wikipedia.org/wiki/Universal_Disk_Format" title="Universal Disk Format">UDF</a>, and as of <a href="http://en.wikipedia.org/wiki/Windows_Vista" title="Windows Vista">Windows Vista</a>, <a href="http://en.wikipedia.org/wiki/NTFS" title="NTFS">NTFS</a>
is the only file system which the operating system can be installed on.
It is possible to install GNU/Linux onto many types of file systems.
Unlike other operating systems, GNU/Linux and UNIX allow any file system
to be used regardless of the media it is stored in, whether it is a
hard drive, a disc (CD,DVD...), a USB flash drive, or even contained
within a file located on another file system.<br />
<h4>
<span class="editsection"></span> <span class="mw-headline" id="Device_drivers">Device drivers</span></h4>
<div class="rellink relarticle mainarticle">
Main article: <a href="http://en.wikipedia.org/wiki/Device_driver" title="Device driver">Device driver</a></div>
A <a href="http://en.wikipedia.org/wiki/Device_driver" title="Device driver">device driver</a>
is a specific type of computer software developed to allow interaction
with hardware devices. Typically this constitutes an interface for
communicating with the device, through the specific computer bus or
communications subsystem that the hardware is connected to, providing
commands to and/or receiving data from the device, and on the other end,
the requisite interfaces to the operating system and software
applications. It is a specialized hardware-dependent computer program
which is also operating system specific that enables another program,
typically an operating system or applications software package or
computer program running under the operating system kernel, to interact
transparently with a hardware device, and usually provides the requisite
interrupt handling necessary for any necessary asynchronous
time-dependent hardware interfacing needs.<br />
The key design goal of device drivers is <a href="http://en.wikipedia.org/wiki/Abstraction" title="Abstraction">abstraction</a>.
Every model of hardware (even within the same class of device) is
different. Newer models also are released by manufacturers that provide
more reliable or better performance and these newer models are often
controlled differently. Computers and their operating systems cannot be
expected to know how to control every device, both now and in the
future. To solve this problem, operating systems essentially dictate how
every type of device should be controlled. The function of the device
driver is then to translate these operating system mandated function
calls into device specific calls. In theory a new device, which is
controlled in a new manner, should function correctly if a suitable
driver is available. This new driver will ensure that the device appears
to operate as usual from the operating system's point of view.<br />
Under versions of Windows before Vista and versions of Linux before
2.6, all driver execution was co-operative, meaning that if a driver
entered an infinite loop it would freeze the system. More recent
revisions of these operating systems incorporate kernel preemption,
where the kernel interrupts the driver to give it tasks, and then
separates itself from the process until it receives a response from the
device driver, or gives it more tasks to do.<br />
<h3>
<span class="editsection"></span> <span class="mw-headline" id="Networking">Networking</span></h3>
<div class="rellink relarticle mainarticle">
Main article: <a href="http://en.wikipedia.org/wiki/Computer_network" title="Computer network">Computer network</a></div>
Currently most operating systems support a variety of networking
protocols, hardware, and applications for using them. This means that
computers running dissimilar operating systems can participate in a
common <a href="http://en.wikipedia.org/wiki/Computer_network" title="Computer network">network</a> for sharing resources such as <a href="http://en.wikipedia.org/wiki/Remote_procedure_call" title="Remote procedure call">computing</a>,
files, printers, and scanners using either wired or wireless
connections. Networks can essentially allow a computer's operating
system to access the resources of a remote computer to support the same
functions as it could if those resources were connected directly to the
local computer. This includes everything from simple communication, to
using networked file systems or even sharing another computer's graphics
or sound hardware. Some network services allow the resources of a
computer to be accessed transparently, such as <a href="http://en.wikipedia.org/wiki/Secure_Shell" title="Secure Shell">SSH</a> which allows networked users direct access to a computer's command line interface.<br />
Client/server networking allows a program on a computer, called a
client, to connect via a network to another computer, called a server.
Servers offer (or host) various services to other network computers and
users. These services are usually provided through ports or numbered
access points beyond the server's <a href="http://en.wikipedia.org/wiki/IP_address" title="IP address">network address</a>.
Each port number is usually associated with a maximum of one running
program, which is responsible for handling requests to that port. A
daemon, being a user program, can in turn access the local hardware
resources of that computer by passing requests to the operating system
kernel.<br />
Many operating systems support one or more vendor-specific or open networking protocols as well, for example, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Systems_Network_Architecture" title="Systems Network Architecture">SNA</a> on <a href="http://en.wikipedia.org/wiki/IBM" title="IBM">IBM</a> systems, <a href="http://en.wikipedia.org/wiki/DECnet" title="DECnet">DECnet</a> on systems from <a href="http://en.wikipedia.org/wiki/Digital_Equipment_Corporation" title="Digital Equipment Corporation">Digital Equipment Corporation</a>, and Microsoft-specific protocols (<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Server_message_block" title="Server message block">SMB</a>) on Windows. Specific protocols for specific tasks may also be supported such as <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Network_File_System_%28protocol%29" title="Network File System (protocol)">NFS</a> for file access. Protocols like <a href="http://en.wikipedia.org/wiki/ESound" title="ESound">ESound</a>, or esd can be easily extended over the network to provide sound from local applications, on a remote system's sound hardware.<br />
<h3>
<span class="editsection"></span> <span class="mw-headline" id="Security">Security</span></h3>
<div class="rellink relarticle mainarticle">
Main article: <a href="http://en.wikipedia.org/wiki/Computer_security" title="Computer security">Computer security</a></div>
A computer being secure depends on a number of technologies working
properly. A modern operating system provides access to a number of
resources, which are available to software running on the system, and to
external devices like networks via the kernel.<br />
The operating system must be capable of distinguishing between
requests which should be allowed to be processed, and others which
should not be processed. While some systems may simply distinguish
between "privileged" and "non-privileged", systems commonly have a form
of requester <i>identity</i>, such as a user name. To establish identity there may be a process of <i>authentication</i>.
Often a username must be quoted, and each username may have a password.
Other methods of authentication, such as magnetic cards or biometric
data, might be used instead. In some cases, especially connections from
the network, resources may be accessed with no authentication at all
(such as reading files over a network share). Also covered by the
concept of requester <b>identity</b> is <i>authorization</i>; the
particular services and resources accessible by the requester once
logged into a system are tied to either the requester's user account or
to the variously configured groups of users to which the requester
belongs.<br />
In addition to the allow/disallow model of security, a system with a
high level of security will also offer auditing options. These would
allow tracking of requests for access to resources (such as, "who has
been reading this file?"). Internal security, or security from an
already running program is only possible if all possibly harmful
requests must be carried out through interrupts to the operating system
kernel. If programs can directly access hardware and resources, they
cannot be secured.<br />
External security involves a request from outside the computer, such
as a login at a connected console or some kind of network connection.
External requests are often passed through device drivers to the
operating system's kernel, where they can be passed onto applications,
or carried out directly. Security of operating systems has long been a
concern because of highly sensitive data held on computers, both of a
commercial and military nature. The United States <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Government_of_the_United_States" title="Government of the United States">Government</a> <a href="http://en.wikipedia.org/wiki/United_States_Department_of_Defense" title="United States Department of Defense">Department of Defense</a> (DoD) created the <i><a href="http://en.wikipedia.org/wiki/Trusted_Computer_System_Evaluation_Criteria" title="Trusted Computer System Evaluation Criteria">Trusted Computer System Evaluation Criteria</a></i>
(TCSEC) which is a standard that sets basic requirements for assessing
the effectiveness of security. This became of vital importance to
operating system makers, because the TCSEC was used to evaluate,
classify and select computer systems being considered for the
processing, storage and retrieval of sensitive or <a href="http://en.wikipedia.org/wiki/Classified_information" title="Classified information">classified information</a>.<br />
Network services include offerings such as file sharing, print services, email, web sites, and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/File_transfer_protocol" title="File transfer protocol">file transfer protocols</a> (FTP), most of which can have compromised security. At the front line of security are hardware devices known as <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Firewall_%28networking%29" title="Firewall (networking)">firewalls</a>
or intrusion detection/prevention systems. At the operating system
level, there are a number of software firewalls available, as well as
intrusion detection/prevention systems. Most modern operating systems
include a software firewall, which is enabled by default. A software
firewall can be configured to allow or deny network traffic to or from a
service or application running on the operating system. Therefore, one
can install and be running an insecure service, such as Telnet or FTP,
and not have to be threatened by a security breach because the firewall
would deny all traffic trying to connect to the service on that port.<br />
An alternative strategy, and the only <a href="http://en.wikipedia.org/wiki/Sandbox_%28computer_security%29" title="Sandbox (computer security)">sandbox</a> strategy available in systems that do not meet the <a href="http://en.wikipedia.org/wiki/Popek_and_Goldberg_virtualization_requirements" title="Popek and Goldberg virtualization requirements">Popek and Goldberg virtualization requirements</a>, is the operating system not running user programs as native code, but instead either <a href="http://en.wikipedia.org/wiki/Emulator" title="Emulator">emulates</a> a processor or provides a host for a <a href="http://en.wikipedia.org/wiki/P-code_machine" title="P-code machine">p-code</a> based system such as Java.<br />
Internal security is especially relevant for multi-user systems; it
allows each user of the system to have private files that the other
users cannot tamper with or read. Internal security is also vital if
auditing is to be of any use, since a program can potentially bypass the
operating system, inclusive of bypassing auditing.<br />
<h3>
<span class="editsection"></span> <span class="mw-headline" id="User_interface">User interface</span></h3>
<div class="thumb tright">
<div class="thumbinner" style="width: 258px;">
<a class="image" href="http://en.wikipedia.org/wiki/File:Command_line.png"><img alt="" class="thumbimage" height="219" src="http://upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Command_line.png/256px-Command_line.png" width="256" /></a>
<br />
<div class="thumbcaption">
<div class="magnify">
<a class="internal" href="http://en.wikipedia.org/wiki/File:Command_line.png" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.18/common/images/magnify-clip.png" width="15" /></a></div>
A screenshot of the <a href="http://en.wikipedia.org/wiki/Bash_%28Unix_shell%29" title="Bash (Unix shell)">Bourne Again Shell</a>
command line. Each command is typed out after the 'prompt', and then
its output appears below, working its way down the screen. The current
command prompt is at the bottom.</div>
</div>
</div>
<div class="rellink relarticle mainarticle">
Main article: <a href="http://en.wikipedia.org/wiki/User_interface" title="User interface">User interface</a></div>
Every computer that is to be operated by an individual requires a <a href="http://en.wikipedia.org/wiki/User_interface" title="User interface">user interface</a>.
The user interface is not actually a part of the operating system—it
generally runs in a separate program usually referred to as a <a href="http://en.wikipedia.org/wiki/Shell_%28computing%29" title="Shell (computing)">shell</a>,
but is essential if human interaction is to be supported. The user
interface requests services from the operating system that will acquire
data from <a href="http://en.wikipedia.org/wiki/Input_device" title="Input device">input hardware devices</a>, such as a <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Keyboard_%28computing%29" title="Keyboard (computing)">keyboard</a>, <a href="http://en.wikipedia.org/wiki/Mouse_%28computing%29" title="Mouse (computing)">mouse</a> or <a href="http://en.wikipedia.org/wiki/Credit_card" title="Credit card">credit card reader</a>, and requests operating system services to display <a href="http://en.wikipedia.org/wiki/Command-line_interface#Command_prompt" title="Command-line interface">prompts</a>, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Status_message" title="Status message">status messages</a> and such on <a href="http://en.wikipedia.org/wiki/Output_device" title="Output device">output hardware devices</a>, such as a <a href="http://en.wikipedia.org/wiki/Computer_monitor" title="Computer monitor">video monitor</a> or <a href="http://en.wikipedia.org/wiki/Printer_%28computing%29" title="Printer (computing)">printer</a>. The two most common forms of a user interface have historically been the <a href="http://en.wikipedia.org/wiki/Command-line_interface" title="Command-line interface">command-line interface</a>, where computer commands are typed out line-by-line, and the <a href="http://en.wikipedia.org/wiki/Graphical_user_interface" title="Graphical user interface">graphical user interface</a>, where a visual environment (most commonly a <a href="http://en.wikipedia.org/wiki/WIMP_%28computing%29" title="WIMP (computing)">WIMP</a>) is present.<br />
<h4>
<span class="editsection"></span> <span class="mw-headline" id="Graphical_user_interfaces">Graphical user interfaces</span></h4>
<div class="thumb tleft">
<div class="thumbinner" style="width: 258px;">
<a class="image" href="http://en.wikipedia.org/wiki/File:KDE_4.png"><img alt="" class="thumbimage" height="144" src="http://upload.wikimedia.org/wikipedia/commons/thumb/5/54/KDE_4.png/256px-KDE_4.png" width="256" /></a>
<br />
<div class="thumbcaption">
<div class="magnify">
<a class="internal" href="http://en.wikipedia.org/wiki/File:KDE_4.png" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.18/common/images/magnify-clip.png" width="15" /></a></div>
A screenshot of the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/K_Desktop_Environment" title="K Desktop Environment">KDE</a>
graphical user interface. Programs take the form of images on the
screen, and the files, folders (directories), and applications take the
form of icons and symbols. A mouse is used to navigate the computer.</div>
</div>
</div>
Most of the modern computer systems support <a href="http://en.wikipedia.org/wiki/Graphical_user_interface" title="Graphical user interface">graphical user interfaces</a> (GUI), and often include them. In some computer systems, such as the original implementation of <a href="http://en.wikipedia.org/wiki/Mac_OS" title="Mac OS">Mac OS</a>, the GUI is integrated into the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Kernel_%28computer_science%29" title="Kernel (computer science)">kernel</a>.<br />
While technically a graphical user interface is not an operating
system service, incorporating support for one into the operating system
kernel can allow the GUI to be more responsive by reducing the number of
<a href="http://en.wikipedia.org/wiki/Context_switch" title="Context switch">context switches</a> required for the GUI to perform its output functions. Other operating systems are <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Modularity_%28programming%29" title="Modularity (programming)">modular</a>,
separating the graphics subsystem from the kernel and the Operating
System. In the 1980s UNIX, VMS and many others had operating systems
that were built this way. GNU/Linux and Mac OS X are also built this
way. Modern releases of Microsoft Windows such as <a href="http://en.wikipedia.org/wiki/Windows_Vista" title="Windows Vista">Windows Vista</a> implement a graphics subsystem that is mostly in user-space; however the graphics drawing routines of versions between <a href="http://en.wikipedia.org/wiki/Windows_NT_4.0" title="Windows NT 4.0">Windows NT 4.0</a> and <a href="http://en.wikipedia.org/wiki/Windows_Server_2003" title="Windows Server 2003">Windows Server 2003</a> exist mostly in kernel space. <a href="http://en.wikipedia.org/wiki/Windows_9x" title="Windows 9x">Windows 9x</a> had very little distinction between the interface and the kernel.<br />
Many computer operating systems allow the user to install or create any user interface they desire. The <a href="http://en.wikipedia.org/wiki/X_Window_System" title="X Window System">X Window System</a> in conjunction with <a href="http://en.wikipedia.org/wiki/GNOME" title="GNOME">GNOME</a> or <a href="http://en.wikipedia.org/wiki/KDE" title="KDE">KDE</a> is a commonly found setup on most Unix and <a href="http://en.wikipedia.org/wiki/Unix-like" title="Unix-like">Unix-like</a> (BSD, GNU/Linux, Solaris) systems. A number of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Windows_shell_replacement" title="Windows shell replacement">Windows shell replacements</a> have been released for Microsoft Windows, which offer alternatives to the included <a href="http://en.wikipedia.org/wiki/Windows_shell" title="Windows shell">Windows shell</a>, but the shell itself cannot be separated from Windows.<br />
Numerous Unix-based GUIs have existed over time, most derived from
X11. Competition among the various vendors of Unix (HP, IBM, Sun) led to
much fragmentation, though an effort to standardize in the 1990s to <a href="http://en.wikipedia.org/wiki/Common_Open_Software_Environment" title="Common Open Software Environment">COSE</a> and <a href="http://en.wikipedia.org/wiki/Common_Desktop_Environment" title="Common Desktop Environment">CDE</a> failed for various reasons, and were eventually eclipsed by the widespread adoption of GNOME and KDE. Prior to <a href="http://en.wikipedia.org/wiki/Free_software" title="Free software">free software</a>-based
toolkits and desktop environments, Motif was the prevalent
toolkit/desktop combination (and was the basis upon which CDE was
developed).<br />
Graphical user interfaces evolve over time. For example, Windows has
modified its user interface almost every time a new major version of
Windows is released, and the Mac OS GUI changed dramatically with the
introduction of Mac OS X in 1999.<sup class="reference" id="cite_ref-intro-date_23-0"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-intro-date-23">[24]</a></sup><br />
<h2>
<span class="editsection"></span> <span class="mw-headline" id="Real-time_operating_systems">Real-time operating systems</span></h2>
<div class="rellink relarticle mainarticle">
Main article: <a href="http://en.wikipedia.org/wiki/Real-time_operating_system" title="Real-time operating system">Real-time operating system</a></div>
A real-time operating system (RTOS) is a multitasking operating system intended for applications with fixed deadlines (<a href="http://en.wikipedia.org/wiki/Real-time_computing" title="Real-time computing">real-time computing</a>). Such applications include some small <a href="http://en.wikipedia.org/wiki/Embedded_system" title="Embedded system">embedded systems</a>, automobile engine controllers, industrial robots, spacecraft, industrial control, and some large-scale computing systems.<br />
An early example of a large-scale real-time operating system was <a href="http://en.wikipedia.org/wiki/Transaction_Processing_Facility" title="Transaction Processing Facility">Transaction Processing Facility</a> developed by <a href="http://en.wikipedia.org/wiki/American_Airlines" title="American Airlines">American Airlines</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/International_Business_Machines" title="International Business Machines">IBM</a> for the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Sabre_Airline_Reservations_System" title="Sabre Airline Reservations System">Sabre Airline Reservations System</a>.<br />
Embedded systems that have fixed deadlines use a <a href="http://en.wikipedia.org/wiki/Real-time_operating_system" title="Real-time operating system">real-time operating system</a> such as <a href="http://en.wikipedia.org/wiki/VxWorks" title="VxWorks">VxWorks</a>, <a href="http://en.wikipedia.org/wiki/PikeOS" title="PikeOS">PikeOS</a>, <a href="http://en.wikipedia.org/wiki/ECos" title="ECos">eCos</a>, <a href="http://en.wikipedia.org/wiki/QNX" title="QNX">QNX</a>, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/MontaVista_Linux" title="MontaVista Linux">MontaVista Linux</a> and <a href="http://en.wikipedia.org/wiki/RTLinux" title="RTLinux">RTLinux</a>. <a href="http://en.wikipedia.org/wiki/Windows_CE" title="Windows CE">Windows CE</a> is a <a href="http://en.wikipedia.org/wiki/Real-time_operating_system" title="Real-time operating system">real-time operating system</a> that shares similar APIs to desktop Windows but shares none of desktop Windows' codebase<sup class="Template-Fact" style="white-space: nowrap;">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources from March 2009">citation needed</span></a></i>]</sup>. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Symbian_OS" title="Symbian OS">Symbian OS</a> also has an RTOS kernel (EKA2) starting with version 8.0b.<br />
Some embedded systems use operating systems such as <a href="http://en.wikipedia.org/wiki/Palm_OS" title="Palm OS">Palm OS</a>, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/BSD_%28operating_system%29" title="BSD (operating system)">BSD</a>, and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/GNU/Linux" title="GNU/Linux">GNU/Linux</a>, although such operating systems do not support real-time computing.<br />
<h2>
<span class="editsection"></span> <span class="mw-headline" id="Operating_system_development_as_a_hobby">Operating system development as a hobby</span></h2>
Operating system development is one of the most complicated
activities in which a computing hobbyist may engage. A hobby operating
system may be classified as one whose code has not been directly derived
from an existing operating system, and has few users and <a href="http://en.wikipedia.org/wiki/Software_development" title="Software development">active developers</a>. <sup class="reference" id="cite_ref-24"><a href="http://en.wikipedia.org/wiki/Operating_system#cite_note-24">[25]</a></sup><br />
In some cases, hobby development is in support of a "<a href="http://en.wikipedia.org/wiki/Homebrew" title="Homebrew">homebrew</a>" computing device, for example, a simple <a href="http://en.wikipedia.org/wiki/Single-board_computer" title="Single-board computer">single-board computer</a> powered by a <a class="mw-redirect" href="http://en.wikipedia.org/wiki/6502_microprocessor" title="6502 microprocessor">6502 microprocessor</a>.
Or, development may be for an architecture already in widespread use.
Operating system development may come from entirely new concepts, or may
commence by modeling an existing operating system. In either case, the
hobbyist is his/her own developer, or may interact with a small and
sometimes unstructured group of individuals who have like interests.<br />
Examples of a hobby operating system include <a href="http://en.wikipedia.org/wiki/ReactOS" title="ReactOS">ReactOS</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Syllable_%28operating_system%29" title="Syllable (operating system)">Syllable</a>.<br />
<h2>
<span class="editsection"></span> <span class="mw-headline" id="Diversity_of_operating_systems_and_portability">Diversity of operating systems and portability</span></h2>
Application software is generally written for use on a specific
operating system, and sometimes even for specific hardware. When porting
the application to run on another OS, the functionality required by
that application may be implemented differently by that OS (the names of
functions, meaning of arguments, etc.) requiring the application to be
adapted, changed, or otherwise <a href="http://en.wikipedia.org/wiki/Software_maintenance" title="Software maintenance">maintained</a>.<br />
This cost in supporting operating systems diversity can be avoided by instead writing applications against <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Software_platform" title="Software platform">software platforms</a> like <a href="http://en.wikipedia.org/wiki/Java_%28software_platform%29" title="Java (software platform)">Java</a>, or <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Qt_%28toolkit%29" title="Qt (toolkit)">Qt</a> for web browsers. These abstractions have already borne the cost of adaptation to specific operating systems and their <a class="mw-redirect" href="http://en.wikipedia.org/wiki/System_library" title="System library">system libraries</a>.<br />
Another approach is for operating system vendors to adopt standards. For example, <a href="http://en.wikipedia.org/wiki/POSIX" title="POSIX">POSIX</a> and <a href="http://en.wikipedia.org/wiki/Operating_System_Abstraction_Layer" title="Operating System Abstraction Layer">OS abstraction layers</a> provide commonalities that reduce porting costs.indrahttp://www.blogger.com/profile/06942992661543821548noreply@blogger.com0tag:blogger.com,1999:blog-8816665326960224272.post-81021598699218294672012-02-01T00:01:00.000-08:002012-02-01T00:01:42.858-08:00iphone5: iPhone 5 Release Dateby on January 9, 2012 in iP...<a href="http://indrateen.blogspot.com/2012/01/iphone-5-release-date-by-on-january-9.html?spref=bl">iphone5: iPhone 5 Release Dateby on January 9, 2012 in iP...</a>: iPhone 5 Release Date by on January 9, 2012 in iPhone 5 News with 17 Comments Each year Apple makes its...indrahttp://www.blogger.com/profile/06942992661543821548noreply@blogger.com0tag:blogger.com,1999:blog-8816665326960224272.post-53944095105436909572012-01-26T18:19:00.000-08:002012-01-26T18:19:34.255-08:00<div class="post-17 post type-post status-publish format-standard sticky hentry category-iphone-5-news" id="post-17">
<h2 class="entry-title">
<a href="http://www.iphone5source.org/iphone-5-release-date" rel="bookmark" style="color: #890002;" title="Permanent Link to iPhone 5 Release Date"> iPhone 5 Release Date</a></h2>
<div class="entry-meta entry-header">
by on January 9, 2012 in <a href="http://www.iphone5source.org/category/iphone-5-news" rel="category tag" title="View all posts in iPhone 5 News">iPhone 5 News</a> with <a href="http://www.iphone5source.org/iphone-5-release-date#comments" title="Comment on iPhone 5 Release Date">17 Comments</a>
</div>
<div class="post-thumb post-lead">
<a href="http://www.iphone5source.org/iphone-5-release-date" title="Permanent Link to iPhone 5 Release Date"><img alt="iphone5releasedate" class="attachment-archive-thumb wp-post-image" height="300" src="http://www.iphone5source.org/wp-content/uploads/2011/12/iphone5releasedate-570x300.jpg" style="background-color: #fcfcfc; border-color: rgb(200, 200, 194);" title="iphone5releasedate" width="570" /></a>
</div>
<div class="entry-content">
Each year Apple makes its presence widely known by releasing a new or
updated version of the iPhone. 2012 promises to be when the iPhone 5
release date is going to be officially announced.<br />
As in keeping with previous traditions for releasing earlier versions of the <a href="http://en.wikipedia.org/wiki/Device">device</a>,
it’s appearing that Apple is going to release the iPhone 5 in the fall.
Rumors about what the iPhone 5 is going to look like or the components
that it is going to have are scattered, but it appears that the case is
going to have either plastic or aluminum along the back. It is also
rumored that it’s going to extend around the front of the iPhone 5 for a
more uniform appearance all around that gives the back more protection
from falls and shock.<br />
<a class="more-link" href="http://www.iphone5source.org/iphone-5-release-date#more-17">Continue reading →</a></div>
</div>
<div class="post-86 post type-post status-publish format-standard hentry category-iphone-5-news tag-4g tag-iphone-5 tag-iphone-5-release-date tag-lte" id="post-86">
<h2 class="entry-title">
<a href="http://www.iphone5source.org/iphone-5-to-have-4g-lte" rel="bookmark" style="color: #890002;" title="Permanent Link to iPhone 5 to have 4G LTE"> iPhone 5 to have 4G LTE</a></h2>
<div class="entry-meta entry-header">
by on January 25, 2012 in <a href="http://www.iphone5source.org/category/iphone-5-news" rel="category tag" title="View all posts in iPhone 5 News">iPhone 5 News</a> with <a href="http://www.iphone5source.org/iphone-5-to-have-4g-lte#respond" title="Comment on iPhone 5 to have 4G LTE">No comments</a>
</div>
<div class="post-thumb post-lead">
<a href="http://www.iphone5source.org/iphone-5-to-have-4g-lte" title="Permanent Link to iPhone 5 to have 4G LTE"><img alt="apple-iphone-5" class="attachment-archive-thumb wp-post-image" height="300" src="http://www.iphone5source.org/wp-content/uploads/2011/12/apple-iphone-5-570x300.jpg" style="background-color: #fcfcfc; border-color: rgb(200, 200, 194);" title="apple-iphone-5" width="570" /></a>
</div>
<div class="entry-content">
Long considered to be the mobile community’s “next
generation” technology, 4G LTE compatibility is being said to be a very
real possibility when it comes to the <b>iPhone 5 release date </b>hits later this fall.<br />
The reality of LTE may be realized within the next few months when
Apple’s iPad 3 hits the market. In the last week, Bloomberg released
several reports citing that the iPad 3 is currently being produced and
will truly feature LTE technology. Should this happen with the iPad 3,
it’s more than likely that the iPhone 5 will also include 4G LTE as
well.<br />
It’s worth noting that a survey that was conducted a few days or
months after the release date of the iPhone 4S highlighted what users
considered as lacking in the expectations not becauce of its screen
size, but beacuse of its lack of LTE. This served as an indication that
the mobile community is ready to consider the 4G LTE as the new
standard.<br />
<h3>
iPhone 5</h3>
Mobile networks in the United States seems to be in agreement with
this as Sprint and Verizon have spent a lot of resources just to execute
the infrastructure of the 4G LTE network. As for AT&T, the network
has been working in a low profile with its very own LTE endeavors.
Regardless of the amount of effort the three big networks are putting to
have LTE, it is without a doubt that they are preparing a real 4G
network with iPhone 5′s release.<br />
Right now, what most consumers need is an LTE operating iPhone 5.
Reports support this by saying that the upcoming iPhone device that will
feature LTE will effectively place the 4G LTE on the level that is
considered as the novel standard in mobile communications.<br />
This means that if Apple launches an iPhone 5 with LTE and is able to
sell millions of units, LTE will surely be an increasing part of the
smartphone pie. What this simply implies is that iPhone 5 will be LTE’s
game changer just like how iPad pioneered the tablet and the first
iPhone led the way to the smartphone that is currently known to many.</div>
</div>
<h2 class="entry-title">
<a href="http://www.iphone5source.org/iphone-5-release-date-speculation" rel="bookmark" style="color: #890002;" title="Permanent Link to iPhone 5 Release Date Speculation"> iPhone 5 Release Date Speculation</a></h2>
<div class="entry-meta entry-header">
by on January 15, 2012 in <a href="http://www.iphone5source.org/category/iphone-5-news" rel="category tag" title="View all posts in iPhone 5 News">iPhone 5 News</a> with <a href="http://www.iphone5source.org/iphone-5-release-date-speculation#respond" title="Comment on iPhone 5 Release Date Speculation">No comments</a>
</div>
<div class="post-thumb post-lead">
<a href="http://www.iphone5source.org/iphone-5-release-date-speculation" title="Permanent Link to iPhone 5 Release Date Speculation"><img alt="apple-iphone-5" class="attachment-archive-thumb wp-post-image" height="300" src="http://www.iphone5source.org/wp-content/uploads/2011/12/apple-iphone-5-570x300.jpg" style="background-color: #fcfcfc; border-color: rgb(200, 200, 194);" title="apple-iphone-5" width="570" /></a>
</div>
There has been much speculation on the iphone 5 and whether
or not it will be the final Steve Jobs release. The iphone 5 is said to
have more features than the current iphone and is much thinner. The
actual iphone 5 release date is unknown but some rumors are speculating
that it should arrive between mid or fall of 2012.<br />
The new iphone is said to have an A6 dual processor and included with that, a 10 megapixel camera. Other features on the <b>iphone 5</b>
such as the button placement haven’t changed much compared to the
current iphone, expect that the buttons are square. Also included is a
hold button located above the 3.5mm jack. The covering is expected to be
made from either plastic or aluminum in order to give the iphone a more
uniform look, and to protect the phone overall from falls or shock.The
designer of this recent technology is said to be Antonio De Rosa.<br />
<h3>
iPhone 5 Release Date</h3>
<a href="http://www.iphone5source.org/iphone-5-concept-photos">Concept photos of the iphone 5 have been released</a>
to excite and encourage fans. The founder of Apple computers, Steve
Jobs passed away October 2011 when he lost the fight to cancer. The full
name of the new iphone is the iphone 5SJ in honor of the well renowned
owner, Steve Jobs. Other gossip of the release delay is said that the
iphone 5 is not compatible with 4G LTE. However, many readings state
that it will be compatible with the 4G LTE network. Another amazing
feature for the iphone 5 is that the screen is much larger and its
design is lightweight. The iphone 5 is rumored to have a new operating
system created by Apple called iOs 5. This will allow the user to have a
more satisfying calling or receiving calls experience compared to the
iphone 4.<br />
<a class="more-link" href="http://www.iphone5source.org/iphone-5-release-date-speculation#more-77">Continue reading →</a>indrahttp://www.blogger.com/profile/06942992661543821548noreply@blogger.com0