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<!doctype html> <html lang="en"> <head> <title>BIOS Definition - What is a BIOS?</title> <link rel="canonical" href="https://techterms.com/definition/bios"> <meta name="description" content="Learn about BIOS firmware and its role during the boot sequence."> <meta name="keywords" content="BIOS, Basic Input/Output System, definition, ROM, RAM, boot, operating system, setup, boot disk, settings, configuration"> <meta name="robots" content="max-image-preview:large"> <meta name="viewport" content="width=device-width, initial-scale=1"> <meta name="apple-itunes-app" content="app-id=923672016"> <meta charset="utf-8"> <link rel="preconnect" href="https://www.google-analytics.com"> <link rel="preconnect" href="securepubads.g.doubleclick.net"> <link rel="preconnect" href="https://www.googletagservices.com"> <link rel="stylesheet" href="https://techterms.com/css/tt.css?v=1" media="screen, print"> <link rel="icon" href="/svg/favicon.svg"> <script>window.dataLayer=window.dataLayer||[];function gtag(){dataLayer.push(arguments)}gtag('consent','default',{'ad_storage':'granted','ad_user_data':'granted','ad_personalization':'granted','analytics_storage':'granted'});gtag('consent','default',{'ad_storage':'denied','ad_user_data':'denied','ad_personalization':'denied','region':["NO","DE","FI","BE","PT","BG","DK","LT","LU","LV","HR","FR","HU","SE","SI","MC","SK","MF","SM","YT","IE","GF","EE","MQ","MT","GP","IS","GR","IT","ES","AT","RE","CY","CZ","AX","PL","RO","LI","NL"]})</script> <script>let adsLoaded=!1;function loadAds(){var e,a,t;googletag.cmd.push(function(){googletag.pubads().refresh()}),t=document,e="script",a=t.createElement(e),t=t.getElementsByTagName(e)[0],a.async=1,a.src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js",a.setAttribute("data-ad-client","ca-pub-0087137714961591"),t.parentNode.insertBefore(a,t),adsLoaded=!0}</script> <script async src="https://www.googletagmanager.com/gtag/js?id=G-5K7VMN5PX3"></script> <script>window.dataLayer=window.dataLayer||[];function gtag(){dataLayer.push(arguments)}gtag('js',new Date());gtag('config','G-5K7VMN5PX3')</script> <script>for(var ca=document.cookie.split("; 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It is stored on a (ROM|rom) chip on the computer's (motherboard|motherboard) and provides a user interface for several advanced hardware configuration settings. ","contributor":{"@type":"Person","name":"Brian Pickle","url":"https://techterms.com/authors/brian_pickle"},"alternateName":"Basic Input/Output System","image":"https://techterms.com/img/md/bios_184.png","url":"https://techterms.com/definition/bios"} </script> </head> <body> <div id="full"> <header id="siteheader"> <div class="content"> <a href="#main" class="visuallyhidden">Skip to main content</a> <a href="/" class="logo"><img src="/svg/logo.svg" width="212" height="24" alt="TechTerms.com"></a> <div class="siteheader-middle"> <div class="searchwrapper collapsed"> <form id="search" class="search" action="/search" method="post"> <div class='autocomplete' role='combobox' aria-expanded='false' aria-owns='autocomplete-results'> <input type="text" id="term" name="term" placeholder="Search (e.g. bios, ASCII, cache)" aria-label="Search (e.g. psd, docx, exe, jpg, zip)" autocomplete="off" class='autocomplete-input term' aria-autocomplete='both' aria-controls='autocomplete-results'> <button id="searchsubmit" class="searchsubmit"></button> </div> <ul id='autocomplete-results' class='autocomplete-results hidden' aria-label='Search'> </ul> </form> </div> <a href="/random" class="headerbutton random" id="random"><img src="/svg/random.svg" alt="random" width="16" height="16"></a> <button id="searchtoggle"><img src="/svg/search-white.svg" alt="search" width="18" height="18"></button> </div> <div class="siteheader-right"> <button id="menuopen"><img src="/svg/menu.svg" alt="open menu" width="18" height="16"></button> <nav id="sitemenu" class="collapsed"> <button id="menuclose"><img src="/svg/close.svg" alt="close menu" width="14" height="14"></button> <ul> <li><a href="/browse/">Terms</a></li> <li><a href="/quiz/">Quizzes</a></li> <li><a href="/help/">Help Center</a></li> <li class="mobile"><a href="/random">Random Term</a></li> <li class="settings"><button id="settings"><img src="/svg/settings.svg" alt="settings" width="22" height="22"></button> <div class="settingsmenu"> <fieldset> <legend>Theme</legend> <input id="theme-default" value="default" type="radio" name="theme" checked> <label for="theme-default">Light</label> <input id="theme-dark" value="dark" type="radio" name="theme" > <label for="theme-dark">Dark</label> <input id="theme-hc" value="hc" type="radio" name="theme" > <label for="theme-hc">High Contrast</label> </fieldset> <div class="fontsizewrapper"><label for="fontsize">Font Size<input type="range" id="fontsize" name="fontsize" min="14" max="26" step="2" value="20"></label><span class="currentsize">20</span></div> <button id="resetsettings">Reset</button> </div> </li> </ul> </nav> </div> </div> </header> <main> <div class="adTopLB"> <div id='div-gpt-ad-1589388248615-0'> </div> </div> <div id="main" class="def"> <div id="left"> <div class="card hasheader"> <div class="cardheader"> <div class="breadcrumbs"><a href="/">Home</a><svg viewBox="0 0 9 14" xmlns="http://www.w3.org/2000/svg"><path d="m0 14 9-7-9-7z"/></svg><a href="/category/software">Software Terms</a><svg viewBox="0 0 9 14" xmlns="http://www.w3.org/2000/svg"><path d="m0 14 9-7-9-7z"/></svg>BIOS Definition</div> </div> <article> <h1>BIOS</h1> <div class="adDefRect"> <div id='div-gpt-ad-1589302365809-0'> </div> </div> <p>Stands for "<b>Basic Input/Output System</b>."</p> <p>A computer's BIOS is a <a href="/definition/firmware">firmware</a> program that controls a computer's <a href="/definition/boot_sequence">boot sequence</a>. It is stored on a <a href="/definition/rom">ROM</a> chip on the computer's <a href="/definition/motherboard">motherboard</a> and provides a user interface for several advanced hardware configuration settings. </p> <p>The BIOS is loaded automatically when a computer is first powered on. It runs the computer's boot sequence by scanning for installed <a href="/definition/hardware">hardware</a> components, running the <a href="/definition/post">POST</a> checks, locating the designated<a href="/definition/boot_disk"> boot disk</a>, then loading the <a href="/definition/operating_system">operating system</a> into <a href="/definition/memory">memory</a>. After the operating system loads, the BIOS serves as an intermediary between the <a href="/definition/cpu">CPU</a> and <a href="/definition/io">I/O</a> devices, keeping track of their hardware addresses for the operating system.</p> <figure class="deffig"> <img src="https://techterms.com/img/xl/bios_184.png" alt="A typical BIOS menu screen" width="562" height="304" class="defimg"> <figcaption class="caption">A typical BIOS menu screen</figcaption> </figure> <p>You can access the BIOS interface during startup by pressing a designated keyboard key — generally <span class="button">DELETE</span> or <span class="button">F2</span> — during the POST check or while the manufacturer's logo appears on the screen. Once loaded, the BIOS interface shows system information like the CPU type and <a href="/definition/clock_speed">clock speed</a>, total system <a href="/definition/ram">RAM</a>, and installed <a href="/definition/storagedevice">storage devices</a>. It also provides several menus of customizable settings, allowing you to choose which drive serves at the boot disk, change system power settings, and toggle hardware components like onboard audio and network connections on or off.</p> <p><b>NOTE:</b> BIOS firmware was standard on PCs throughout the 1980s, 1990s, and 2000s until manufacturers started replacing it with a successor, the Unified Extensible Firmware Interface (<a href="/definition/uefi">UEFI</a>), in the 2010s.</p> <div class="adBotLB"> <div id='div-gpt-ad-1589236206757-0'> </div> </div> <div class="cardfooter"> <div class="upDate"><div class="author">Updated <span class="pdate">April 11, 2023</span> by <a href="/authors/brian_pickle">Brian P.</a></div></div><div id="citations"> <div class="tabs"> <div role="tablist" aria-label="citations"> <button role="tab" aria-selected="false" aria-controls="apa" tabindex="-1">APA</button> <button role="tab" aria-selected="false" aria-controls="mla" tabindex="-1">MLA</button> <button 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class="answerCell"><span id="answerA" class="quizAnswer">Dual core</span> <div class="answerBar"> <div id="quizBarA" class="quizBar"></div><span id="quizPercA" class="quizperc">0%</span> </div> </div> </div> <div id="ansButtonB" class="answerButton activeButton" data-answer="Bnum" data-date="2022-12-05"><span class="ansLetter">B</span> <div class="answerCell"><span id="answerB" class="quizAnswer">Dual boot</span> <div class="answerBar"> <div id="quizBarB" class="quizBar"></div><span id="quizPercB" class="quizperc">0%</span> </div> </div> </div> <div id="ansButtonC" class="answerButton activeButton" data-answer="Cnum" data-date="2022-12-05"><span class="ansLetter">C</span> <div class="answerCell"><span id="answerC" class="quizAnswer">Dual load</span> <div class="answerBar"> <div id="quizBarC" class="quizBar"></div><span id="quizPercC" class="quizperc">0%</span> </div> </div> </div> <div id="ansButtonD" class="answerButton activeButton" data-answer="Dnum" data-date="2022-12-05"><span class="ansLetter">D</span> <div class="answerCell"><span id="answerD" class="quizAnswer">Dual launch</span> <div class="answerBar"> <div id="quizBarD" class="quizBar"></div><span id="quizPercD" class="quizperc">0%</span> </div> </div> </div> <div class="quizResult"><div class="qmsg"> <b class="quizPass">Correct!</b> <b class="quizFail">Incorrect!</b>   <span class="customMessage"></span>  View the <a href="/definition/dual_boot">Dual Boot definition</a>.</div> <a href="/quiz/#morequizzes" class="quizNext btnprimary">More Quizzes →</a> </div> </div> </div> </div> </div> </div> <div id="right"> <div class="prevnext"> <a href="biometrics"><span class="arrow">‹</span>  <span class="linktext">Biometrics</span></a><span> | </span><a href="biotech"><span class="linktext">Biotech</span>  <span class="arrow">›</span></a></div> <div class="tf card"> <h2 class="heading">Tech Factor</h2> <a href="/help/tech_factor" class="info" title="What is the Tech Factor?">?</a> <a href="/techfactor/6"><span class="factor">6</span><span class="denom"> / 10</span></a></div> <div class="listBox card related"> <h2 class="heading">Related Terms</h2> <div class="rlists"> <ol> <li><a href="/definition/rom">ROM</a></li> <li><a href="/definition/memory">Memory</a></li> <li><a href="/definition/boot_sequence">Boot Sequence</a></li> <li><a href="/definition/motherboard">Motherboard</a></li> </ol> <ol start="5"><li><a href="/definition/boot_disk">Boot Disk</a></li> <li><a href="/definition/cpu">CPU</a></li> <li><a href="/definition/io">I/O</a></li> <li><a href="/definition/firmware">Firmware</a></li> </ol> </div> </div> <div class="adRightSky"> <div id='div-gpt-ad-1589233879778-0'> </div> </div> </div> <div class="techterms card"> <h2 class="heading">The Tech Terms Computer Dictionary</h2> <p>The definition of BIOS on this page is an original definition written by the <a href="/authors/">TechTerms.com team</a>. 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