CINXE.COM

<!doctype html> <html lang="en"> <head> <title>Function Definition - What is a function in computer programming?</title> <link rel="canonical" href="https://techterms.com/definition/function"> <meta name="description" content="Learn how computer programs use functions to take input parameters, perform a calculation, then return output."> <meta name="keywords" content="Function, definition, computer, program, input, output, parameters, mathematics, subroutine"> <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 src="https://cdn.cookielaw.org/scripttemplates/otSDKStub.js" data-domain-script="018decfc-da98-7112-b546-affa65c740cd"></script> <script>let adsLoaded=!1;let cmpReady=!1;let adsReady=!1;function OptanonWrapper(){cmpReady=!0;loadAds()}function loadAds(){if(!adsLoaded&&cmpReady&&adsReady){if((typeof __tcfapi!=="undefined")||(OnetrustActiveGroups.indexOf('C0004')!=-1)){googletag.cmd.push(function(){googletag.pubads().refresh()});!function(e,t,a,n,o,s){o=e.createElement(t),s=e.getElementsByTagName(t)[0],o.async=1,o.src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js",o.setAttribute("data-ad-client","ca-pub-0087137714961591"),s.parentNode.insertBefore(o,s)}(document,"script")}else{googletag.cmd.push(function(){googletag.pubads().setPrivacySettings({nonPersonalizedAds:!0}),googletag.pubads().refresh()});!function(e,t,a,n,o,s){o=e.createElement(t),s=e.getElementsByTagName(t)[0],o.async=1,o.src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js",o.setAttribute("data-ad-client","ca-pub-0087137714961591"),o.setAttribute("data-privacy-treatments","disablePersonalization"),s.parentNode.insertBefore(o,s)}(document,"script")} 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("; "),i=0;i<ca.length;i++){var c=ca[i];if(-1!=c.indexOf("tt_theme=")){var theme=c.substring(9,c.length),html=document.getElementsByTagName("html")[0];html.classList.add("theme-"+theme),USERTHEME=theme;}else-1!=c.indexOf("tt_size=")&&(USERSIZE=c.substring(8,c.length))}</script> <script async src="https://securepubads.g.doubleclick.net/tag/js/gpt.js"></script> <script>var sizes_tlb = [[970, 90], [728, 90], [468, 60], [320, 100], [320, 50]];var sizes_ss = [[300, 600], [160, 600], [468, 60], [320, 100], [320, 50]];var sizes_ra = [[336, 280], [300, 250], [320, 100], [320, 50]];var sizes_lb = [[728, 90], [468, 60], [320, 100], [320, 50], "fluid"];window.googletag = window.googletag || {cmd: []}; googletag.cmd.push(function() {function defineAdSlot(e,d,g,i){e="/1009901/"+e,g="div-gpt-ad-"+g+"-0",slot0=googletag.defineSlot(e,d,g).defineSizeMapping(i).addService(googletag.pubads())}var mapping_tlb = googletag.sizeMapping().addSize([1000, 0], [[970, 90], [728, 90], [468, 60], [320, 100], [320, 50]]).addSize([758, 0], [[728, 90], [468, 60], [320, 100], [320, 50]]).addSize([488, 0], [[468, 60], [320, 100], [320, 50]]).addSize([0, 0], [[320, 100], [320, 50]]).build();var mapping_ss = googletag.sizeMapping().addSize([981, 0], [[300, 600], [160, 600]]).build();var mapping_ra = googletag.sizeMapping().addSize([971, 0], [[336, 280], [300, 250], [320, 100], [320, 50]]).addSize([551, 0], [[300, 250]]).build();var mapping_lb = googletag.sizeMapping().addSize([1178, 0], [[728, 90], [468, 60], [320, 100], [320, 50], "fluid"]).addSize([966, 0], [[468, 60], [320, 100], [320, 50], "fluid"]).addSize([820, 0], [[728, 90], [468, 60], [320, 100], [320, 50], "fluid"]).addSize([520, 0], [[468, 60], [320, 100], [320, 50], "fluid"]).addSize([0, 0], [[320, 100], [320, 50], "fluid"]).build();var mapping_qlb = googletag.sizeMapping().addSize([758, 0], [[728, 90], [468, 60], [320, 100], [320, 50], "fluid"]).addSize([488, 0], [[468, 60], [320, 100], [320, 50], "fluid"]).addSize([0, 0], [[320, 100], [320, 50], "fluid"]).build();if (window.innerWidth >= 0) defineAdSlot('tt_tlb_2020', sizes_tlb, '1589388248615', mapping_tlb);if (window.innerWidth >= 551) defineAdSlot('tt_dra_2020', sizes_ra, '1589302365809', mapping_ra);if (window.innerWidth >= 0) defineAdSlot('tt_dlb_2020', sizes_lb, '1589236206757', mapping_lb);if (window.innerWidth >= 980) defineAdSlot('tt_dss_2020', sizes_ss, '1589233879778', mapping_ss);});googletag.cmd.push(function(){googletag.pubads().disableInitialLoad(),googletag.pubads().enableSingleRequest(),googletag.pubads().setTargeting("page_url","/definition/function"),googletag.enableServices()});adsReady=true;loadAds();if (window.innerWidth >= 0) googletag.cmd.push(function(){googletag.display("div-gpt-ad-1589388248615-0")});if (window.innerWidth >= 551) googletag.cmd.push(function(){googletag.display("div-gpt-ad-1589302365809-0")});if (window.innerWidth >= 0) googletag.cmd.push(function(){googletag.display("div-gpt-ad-1589236206757-0")});if (window.innerWidth >= 980) googletag.cmd.push(function(){googletag.display("div-gpt-ad-1589233879778-0")});</script> <script type="application/ld+json"> {"@context":"http://schema.org","@type":"Article","dateCreated":"2010-12-28","datePublished":"2010-12-28","dateModified":"2010-12-28","copyrightYear":"2010","copyrightHolder":{"@type":"Organization","name":"Sharpened Productions"},"name":"Function","description":"A technical definition of Function","headline":"Function","abstract":"Definition of Function","author":{"@type":"Person","name":"Per Christensson","url":"https://techterms.com/authors/per_christensson"},"publisher":{"@type":"Organization","name":"TechTerms.com","logo":"https://techterms.com/img/main/techterms.png"},"teaches":{"@type":"DefinedTerm","url":"https://techterms.com/definition/function","name":"Function","description":"A technical definition of Function"},"audience":{"@type":"Audience","audienceType":"everyone"},"genre":"Technology","inLanguage":"en-US","isFamilyFriendly":"True","keywords":"computer, program, input, output, parameters, mathematics, subroutine","locationCreated":{"@type":"Place","name":"United States"},"text":"In mathematics, a function is defined as a relationship between defined values and one or more variables. For example, a simple math function may be:","url":"https://techterms.com/definition/function"} </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. function, 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>Function Definition</div> </div> <article> <h1>Function</h1> <div class="adDefRect"> <div id='div-gpt-ad-1589302365809-0'> </div> </div> <p>In mathematics, a function is defined as a relationship between defined values and one or more variables. For example, a simple math function may be:</p> <p><span class="command">y = 2x</span></p> <p>In this example, the relationship of y to x is that y is twice as much as the value assigned to x. While math functions can be far more complex than this, most are simple relative to functions used in computer programming. This may be why math functions are often referred to as "expressions," while computer functions are often called "procedures" or "subroutines."</p> <p>Computer functions are similar to math functions in that they may reference <a href="/definition/parameter">parameters</a>, which are passed, or <a href="/definition/input">input</a> into the function. If the example above were written as a computer function, "x" would be the input parameter and "y" would be the resulting <a href="/definition/output">output</a> value. It might look something like this:</p> <p><span class="command">function double(x)</span><br> <span class="command">{</span><br> <span class="command">  $y = 2 * x;</span><br> <span class="command">  return $y;</span><br> <span class="command">}</span></p> <p>The above example is a very basic function. Most functions used in computer programs include several lines of instructions and may even reference other functions. A function may also reference itself, in which case it is called a <a href="/definition/recursive_function">recursive function</a>. Some functions may require no parameters, while others may require several. While it is common for functions to return variables, many functions do not return any values, but instead output data as they run.</p> <p>Functions are sometimes considered the building blocks of computer <a href="/definition/program">programs</a>, since they can control both small and large amounts of data. While functions can be called multiple times within a program, they only need to be declared once. Therefore, programmers often create "libraries" of functions that can referenced by one or more programs. Still, the <a href="/definition/source_code">source code</a> of large computer programs may contain hundreds or even thousands of functions.</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">December 28, 2010</span> by <a href="/authors/per_christensson">Per C.</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 role="tab" aria-selected="false" aria-controls="chicago" tabindex="-1">Chicago</button> <button role="tab" aria-selected="false" aria-controls="html" tabindex="-1">HTML</button> <button role="tab" aria-selected="false" aria-controls="link" tabindex="-1">Link</button> </div> <div class="citationwrap"> <div id="apa" role="tabpanel" class="citation" hidden> </div> <div id="mla" role="tabpanel" class="citation" hidden> </div> <div id="chicago" role="tabpanel" class="citation" hidden> </div> <div id="html" role="tabpanel" class="citation" hidden> </div> <div id="link" role="tabpanel" class="citation" hidden> <div>https://techterms.com/definition/function</div> </div> <button id="citecopy"><span class="visuallyhidden">Copy</span><svg enable-background="new 0 0 488.3 488.3" viewBox="-7.5 -7.5 495.8 503.3" xmlns="http://www.w3.org/2000/svg"><path d="m314.25 85.4h-227c-21.3 0-38.6 17.3-38.6 38.6v325.7c0 21.3 17.3 38.6 38.6 38.6h227c21.3 0 38.6-17.3 38.6-38.6v-325.7c-.1-21.3-17.4-38.6-38.6-38.6zm11.5 364.2c0 6.4-5.2 11.6-11.6 11.6h-227c-6.4 0-11.6-5.2-11.6-11.6v-325.6c0-6.4 5.2-11.6 11.6-11.6h227c6.4 0 11.6 5.2 11.6 11.6z" stroke-width="15"/><path d="m401.05 0h-227c-21.3 0-38.6 17.3-38.6 38.6 0 7.5 6 13.5 13.5 13.5s13.5-6 13.5-13.5c0-6.4 5.2-11.6 11.6-11.6h227c6.4 0 11.6 5.2 11.6 11.6v325.7c0 6.4-5.2 11.6-11.6 11.6-7.5 0-13.5 6-13.5 13.5s6 13.5 13.5 13.5c21.3 0 38.6-17.3 38.6-38.6v-325.7c0-21.3-17.3-38.6-38.6-38.6z" stroke-width="15"/></svg></button> </div> </div> </div> </div> </article> </div> <div id="defquiz" class="card"> <h2 class="heading logoheading"><img src="/img/main/quiz.png" alt="quiz" style="width:45px">Test Your Knowledge</h2> <div class="quizBox"> <div class="quizBody"> <p class="quizQuestion">Which of the following archive file formats stores its contents uncompressed?</p> <div class="quizTable"> <div id="ansButtonA" class="answerButton activeButton" data-answer="Anum" data-date="2023-05-05"><span class="ansLetter">A</span> <div class="answerCell"><span id="answerA" class="quizAnswer">RAR</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="2023-05-05"><span class="ansLetter">B</span> <div class="answerCell"><span id="answerB" class="quizAnswer">ZIP</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="2023-05-05"><span class="ansLetter">C</span> <div class="answerCell"><span id="answerC" class="quizAnswer">TAR</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="2023-05-05"><span class="ansLetter">D</span> <div class="answerCell"><span id="answerD" class="quizAnswer">7Z</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/archive">Archive 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="full-duplex"><span class="arrow">‹</span>  <span class="linktext">Full-Duplex</span></a><span> | </span><a href="function_key"><span class="linktext">Function Key</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/5"><span class="factor">5</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/program">Program</a></li> <li><a href="/definition/input">Input</a></li> <li><a href="/definition/output">Output</a></li> </ol> <ol start="4"><li><a href="/definition/parameter">Parameter</a></li> <li><a href="/definition/programming_language">Programming Language</a></li> <li><a href="/definition/library">Library</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 Function on this page is an original definition written by the <a href="/authors/">TechTerms.com team</a>. If you would like to reference this page or cite this definition, please use the green citation links above.</p> <p>The goal of TechTerms.com is to explain computer terminology in a way that is easy to understand. We strive for simplicity and accuracy with every definition we publish. If you have feedback about this definition or would like to suggest a new technical term, please <a href="/contact">contact us</a>.</p> </div> </div> <div class="popupwrapper"> <div id="newsletter_popup"> <button class="close">×</button> <div id="ttnform"> <h3 class="heading">Sign up for the free TechTerms Newsletter</h3> <form id="subscribe"> <div class="field"><label for="newsletter_email">Email (required):</label> <input type="email" id="newsletter_email" name="newsletter_email" required aria-label="email address"> </div> <div class="row1"> <div class="field"><label for="first_name">First Name:</label> <input type="text" name="first_name" id="first_name"></div> <div class="field"><label for="first_name">Last Name:</label> <input type="text" name="last_name" id="last_name"></div> </div> <fieldset class="row2"> <legend>How often would you like to receive an email?</legend> <input type="radio" name="frequency" id="daily" value="d" checked><label for="daily">Daily</label> <input type="radio" name="frequency" id="weekly" value="w"><label for="weekly">Weekly (Every Tuesday)</label> <input type="text" id="newsletter_message" name="message" class="cfieldhid" aria-hidden="true" aria-label="If you are a human, please do not fill in this field." tabindex="-1"> </fieldset> <input type="submit" class="btnprimary" value="Subscribe"> <div id="ttnerror"> </div> <p>You can unsubscribe or change your frequency setting at any time using the links available in each email.<br><br>Questions? Please <a href="/contact">contact us</a>.</p> </form> </div> <div id="ttnconfirm" style="display: none;"> <h3>Thank You</h3> <p>We just sent you an email to confirm your email address. Once you confirm your address, you will begin to receive the newsletter.</p> <p>If you have any questions, please <a href="/contact">contact us</a>.</p> <button class="ok btnprimary">Ok</button> </div> </div> </div> </main> <footer id="sitefooter"><a href="https://sharpened.com/" target="_blank" rel="noopener"><span class="copyright">© 2024 Sharpened Productions</span></a>  |  <a href="/terms">Terms of Use</a>  |  <a href="/privacy">Privacy Policy</a>  |  <button id="ot-sdk-btsn" class="ot-sdk-show-settings">Cookie Settings</button>  |  <a href="/about">About</a>  |  <a href="/contact">Contact</a></footer> </div> <script defer src="https://techterms.com/js/tt.js"></script><script> var cterm = 'Function'; var curl = 'function'; quizDate = '2023-05-05'; T = cterm; C = "a549c830f93ce664583cf1c9eb72f861"; </script> <script defer src="https://techterms.com/js/quiz.js?v=1"></script> </body> </html>