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class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Fortran"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.3</span> <span>Fortran</span> </div> </a> <ul id="toc-Fortran-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-JavaScript" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#JavaScript"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.4</span> <span>JavaScript</span> </div> </a> <ul id="toc-JavaScript-sublist" class="vector-toc-list"> <li id="toc-AngularJS" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#AngularJS"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.4.1</span> <span>AngularJS</span> </div> </a> <ul id="toc-AngularJS-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-jQuery" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#jQuery"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.4.2</span> <span>jQuery</span> </div> </a> <ul id="toc-jQuery-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Lodash" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Lodash"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.4.3</span> <span>Lodash</span> </div> </a> <ul id="toc-Lodash-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Pascal" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Pascal"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.5</span> <span>Pascal</span> </div> </a> <ul id="toc-Pascal-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Python" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Python"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.6</span> <span>Python</span> </div> </a> <ul id="toc-Python-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Shell_scripting_(bash,_zsh,_etc.)" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Shell_scripting_(bash,_zsh,_etc.)"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.7</span> <span>Shell scripting (bash, zsh, etc.)</span> </div> </a> <ul id="toc-Shell_scripting_(bash,_zsh,_etc.)-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-TeX_macro_language_(ConTeXt,_LaTeX,_etc.)" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#TeX_macro_language_(ConTeXt,_LaTeX,_etc.)"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.8</span> <span>TeX macro language (ConTeXt, LaTeX, etc.)</span> </div> </a> <ul id="toc-TeX_macro_language_(ConTeXt,_LaTeX,_etc.)-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-NOP_protocol_commands" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#NOP_protocol_commands"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>NOP protocol commands</span> </div> </a> <ul id="toc-NOP_protocol_commands-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Cracking" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Cracking"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Cracking</span> </div> </a> <ul id="toc-Cracking-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Security_exploits" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Security_exploits"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Security exploits</span> </div> </a> <ul id="toc-Security_exploits-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" title="Table of Contents" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" 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Available in 17 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-17" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">17 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D9%84%D8%A7_%D8%B9%D9%85%D9%84%D9%8A%D8%A9_(%D8%A8%D8%B1%D9%85%D8%AC%D8%A9)" title="لا عملية (برمجة) – Arabic" lang="ar" hreflang="ar" data-title="لا عملية (برمجة)" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/NOP_(codi)" title="NOP (codi) – Catalan" lang="ca" hreflang="ca" data-title="NOP (codi)" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Nulov%C3%A1_operace" title="Nulová operace – Czech" lang="cs" hreflang="cs" data-title="Nulová operace" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Nulloperation" title="Nulloperation – German" lang="de" hreflang="de" data-title="Nulloperation" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/NOP" title="NOP – Spanish" lang="es" hreflang="es" data-title="NOP" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/NOP_(%DA%A9%D8%AF)" title="NOP (کد) – Persian" lang="fa" hreflang="fa" data-title="NOP (کد)" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Instruction_nulle" title="Instruction nulle – French" lang="fr" hreflang="fr" data-title="Instruction nulle" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/NOP_(%EC%BD%94%EB%93%9C)" title="NOP (코드) – Korean" lang="ko" hreflang="ko" data-title="NOP (코드)" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/NOP_(informatica)" title="NOP (informatica) – Italian" lang="it" hreflang="it" data-title="NOP (informatica)" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/NOP_(mnemonische_computerinstructie)" title="NOP (mnemonische computerinstructie) – Dutch" lang="nl" hreflang="nl" data-title="NOP (mnemonische computerinstructie)" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/NOP" title="NOP – Japanese" lang="ja" hreflang="ja" data-title="NOP" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Instrukcja_pusta" title="Instrukcja pusta – Polish" lang="pl" hreflang="pl" data-title="Instrukcja pusta" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/NOP" title="NOP – Portuguese" lang="pt" hreflang="pt" data-title="NOP" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/NOP" title="NOP – Russian" lang="ru" hreflang="ru" data-title="NOP" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/NOP" title="NOP – Ukrainian" lang="uk" hreflang="uk" data-title="NOP" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-zh-yue mw-list-item"><a href="https://zh-yue.wikipedia.org/wiki/NOP" title="NOP – Cantonese" lang="yue" hreflang="yue" data-title="NOP" data-language-autonym="粵語" data-language-local-name="Cantonese" class="interlanguage-link-target"><span>粵語</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/NOP" title="NOP – Chinese" lang="zh" hreflang="zh" data-title="NOP" 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searchaux" style="display:none">Machine instruction that indicates to a computer to do nothing</div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">This article is about the "No Operation" computer instruction. For Null statement, see <a href="/wiki/Null_function" title="Null function">Null function</a>. For Do nothing instruction, see <a href="/wiki/Do_Nothing_(disambiguation)" class="mw-redirect mw-disambig" title="Do Nothing (disambiguation)">Do Nothing (disambiguation)</a>. For other uses, see <a href="/wiki/NOOP_(disambiguation)" class="mw-redirect mw-disambig" title="NOOP (disambiguation)">NOOP (disambiguation)</a> and <a href="/wiki/NOP_(disambiguation)" class="mw-redirect mw-disambig" title="NOP (disambiguation)">NOP (disambiguation)</a>.</div> <style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol ul,.mw-parser-output .hlist ul dl,.mw-parser-output .hlist ul ol,.mw-parser-output .hlist ul ul{display:inline}.mw-parser-output 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a{color:var(--color-progressive)!important}}@media print{body.ns-0 .mw-parser-output .sidebar{display:none!important}}</style><table class="sidebar nomobile nowraplinks" style="margin-top: 0.5em;"><tbody><tr><th class="sidebar-title" style="background-color: rgba(51, 153, 255, 0.15);"><a href="/wiki/Machine_code" title="Machine code">Machine code</a></th></tr><tr><th class="sidebar-heading" style="background-color: rgba(51, 153, 255, 0.15);"> General concepts</th></tr><tr><td class="sidebar-content" style="text-align: left;"> <ul><li><a href="/wiki/Instruction_set_architecture" title="Instruction set architecture">Instruction set</a></li> <li><a href="/wiki/Opcode" title="Opcode">Opcode</a> <ul><li><a href="/wiki/Illegal_opcode" title="Illegal opcode">Illegal opcode</a></li> <li><a href="/wiki/Opcode_table" title="Opcode table">Opcode table</a></li></ul></li> <li><a href="/wiki/Operand#Computer_science" title="Operand">Operand</a></li></ul></td> </tr><tr><th class="sidebar-heading" style="background-color: rgba(51, 153, 255, 0.15);"> Instructions</th></tr><tr><td class="sidebar-content" style="text-align: left;"> <ul><li><a class="mw-selflink selflink">NOP</a></li> <li><a href="/wiki/Branch_(computer_science)" title="Branch (computer science)">Branch</a> <ul><li><a href="/wiki/Indirect_branch" title="Indirect branch">Indirect branch</a></li></ul></li> <li><a href="/wiki/Repeat_instruction" title="Repeat instruction">Repeat instruction</a></li> <li><a href="/wiki/Execute_instruction" title="Execute instruction">Execute instruction</a></li></ul></td> </tr><tr><td class="sidebar-navbar"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374" /><style data-mw-deduplicate="TemplateStyles:r1239400231">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:"[ "}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:" ]"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Machine_code" title="Template:Machine code"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Machine_code" title="Template talk:Machine code"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Machine_code" title="Special:EditPage/Template:Machine code"><abbr title="Edit this template">e</abbr></a></li></ul></div></td></tr></tbody></table> <p>In <a href="/wiki/Computer_science" title="Computer science">computer science</a>, a <b>NOP</b>, <b>no-op</b>, or <b>NOOP</b> (pronounced "no op"; short for <b>no operation</b>) is a <a href="/wiki/Machine_code" title="Machine code">machine language</a> instruction and its <a href="/wiki/Assembly_language" title="Assembly language">assembly language</a> mnemonic, <a href="/wiki/Programming_language" title="Programming language">programming language</a> statement, or <a href="/wiki/Protocol_(computing)" class="mw-redirect" title="Protocol (computing)">computer protocol</a> command that does nothing. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Machine_language_instructions">Machine language instructions</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=NOP_(code)&action=edit&section=1" title="Edit section: Machine language instructions"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Some computer <a href="/wiki/Instruction_set" class="mw-redirect" title="Instruction set">instruction sets</a> include an instruction whose explicit purpose is to not change the state of any of the programmer-accessible <a href="/wiki/Processor_register" title="Processor register">registers</a>, <a href="/wiki/Process_states" class="mw-redirect" title="Process states">status flags</a>, or <a href="/wiki/Main_memory" class="mw-redirect" title="Main memory">memory</a>. It often takes a well-defined number of <a href="/wiki/Clock_cycles" class="mw-redirect" title="Clock cycles">clock cycles</a> to execute. In other instruction sets, there is no explicit NOP instruction, but the assembly language mnemonic NOP represents an instruction which acts as a NOP; e.g., on the <a href="/wiki/SPARC" title="SPARC">SPARC</a>, <code>sethi 0, %g0</code>. </p><p>A NOP must not access memory, as that could cause a <a href="/wiki/Memory_fault" class="mw-redirect" title="Memory fault">memory fault</a> or <a href="/wiki/Page_fault" title="Page fault">page fault</a>. </p><p>A NOP is most commonly used for timing purposes, to force <a href="/wiki/Data_structure_alignment" title="Data structure alignment">memory alignment</a>, to prevent <a href="/wiki/Hazard_(computer_architecture)" title="Hazard (computer architecture)">hazards</a>, to occupy a <a href="/wiki/Branch_delay_slot" class="mw-redirect" title="Branch delay slot">branch delay slot</a>, to render void an existing instruction such as a jump, as a target of an <a href="/wiki/Execute_instruction" title="Execute instruction">execute instruction</a>, or as a place-holder to be replaced by active instructions later on in program development (or to replace removed instructions when reorganizing would be problematic or time-consuming). In some cases, a NOP can have minor side effects; for example, on the <a href="/wiki/Motorola_68000" title="Motorola 68000">Motorola 68000</a> series of processors, the NOP opcode causes a synchronization of the <a href="/wiki/Pipeline_(computing)" title="Pipeline (computing)">pipeline</a>.<sup id="cite_ref-m68ref_1-0" class="reference"><a href="#cite_note-m68ref-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p><p>Listed below are the NOP instruction for some CPU architectures: </p> <style data-mw-deduplicate="TemplateStyles:r1281342579">@media screen{.mw-parser-output .sticky-header>thead>tr:first-child,.mw-parser-output .sticky-header>caption+tbody>tr:first-child,.mw-parser-output .sticky-header>tbody:first-child>tr:first-child,.mw-parser-output .sticky-header-multi>thead{position:sticky;top:0;z-index:10}.mw-parser-output .sticky-header:not(.wikitable),.mw-parser-output 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.sticky-header-multi.wikitable{border-bottom-width:0.2em;padding:0}.mw-parser-output .sticky-header.static-row-numbers.wikitable tr::before,.mw-parser-output .sticky-header-multi.static-row-numbers.wikitable tr::before{border-left-width:1px}.mw-parser-output .sticky-header.static-row-numbers.wikitable>thead>tr:first-child::before,.mw-parser-output .sticky-header.static-row-numbers.wikitable>caption+tbody>tr:first-child::before,.mw-parser-output .sticky-header.static-row-numbers.wikitable>tbody:first-child>tr:first-child::before,.mw-parser-output .sticky-header-multi.static-row-numbers.wikitable>thead>tr:first-child::before,.mw-parser-output .sticky-header-multi.static-row-numbers.wikitable>caption+tbody>tr:first-child::before,.mw-parser-output .sticky-header-multi.static-row-numbers.wikitable>tbody:first-child>tr:first-child::before,.mw-parser-output .sticky-header.static-row-numbers.wikitable .sortbottom::before,.mw-parser-output .sticky-header-multi.static-row-numbers.wikitable .sortbottom::before{border-top-width:1px}.mw-parser-output .sticky-header.static-row-numbers.wikitable .sortbottom~.sortbottom::before,.mw-parser-output .sticky-header-multi.static-row-numbers.wikitable .sortbottom~.sortbottom::before{border-top-width:0}.mw-parser-output .sticky-header.static-row-numbers.wikitable>tbody>tr:not(.static-row-header)::before,.mw-parser-output .sticky-header-multi.static-row-numbers.wikitable>tbody>tr:not(.static-row-header)::before{border-bottom-width:0!important;border-right-width:0!important}body.skin-timeless .mw-parser-output .content-table-scrollbar,body.skin-timeless .mw-parser-output .overflowed,body.skin-timeless .mw-parser-output .overflowed .content-table{overflow:visible}body.skin-timeless .mw-parser-output .scroll-right.overflowed .content-table-right{box-shadow:none;border-left:none}}@media screen and (min-width:1120px){body.vector-sticky-header-visible .mw-parser-output .sticky-header>thead>tr:first-child,body.vector-sticky-header-visible .mw-parser-output .sticky-header>caption+tbody>tr:first-child,body.vector-sticky-header-visible .mw-parser-output .sticky-header>tbody:first-child>tr:first-child,body.vector-sticky-header-visible .mw-parser-output .sticky-header-multi>thead{top:3.125rem}}@media screen and (min-width:851px){body.skin-timeless .mw-parser-output .sticky-header>thead>tr:first-child,body.skin-timeless .mw-parser-output .sticky-header>caption+tbody>tr:first-child,body.skin-timeless .mw-parser-output .sticky-header>tbody:first-child>tr:first-child,body.skin-timeless .mw-parser-output .sticky-header-multi>thead{top:3.51em}}@media screen and (max-width:639px){body.skin-monobook .mw-parser-output .sticky-header,body.skin-monobook .mw-parser-output .sticky-header-multi,body.skin-vector-legacy .mw-parser-output .sticky-header,body.skin-vector-legacy .mw-parser-output .sticky-header-multi,body.skin-vector-2022 .mw-parser-output .sticky-header,body.skin-vector-2022 .mw-parser-output .sticky-header-multi{display:table}}@media screen{html.skin-theme-clientpref-night body.skin-minerva .mw-parser-output .sticky-header-multi.wikitable{background-color:#101418}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os body.skin-minerva .mw-parser-output .sticky-header-multi.wikitable{background-color:#101418}}</style> <table class="wikitable sticky-header" border="1"> <tbody><tr> <th>CPU architecture </th> <th>Instruction <a href="/wiki/Mnemonic" title="Mnemonic">mnemonic</a> </th> <th><a href="/wiki/Byte" title="Byte">Bytes</a> </th> <th><a href="/wiki/Opcode" title="Opcode">Opcode</a> </th> <th>Notes </th></tr> <tr> <td rowspan="2"><a href="/wiki/Intel" title="Intel">Intel</a> <a href="/wiki/X86" title="X86">x86</a> <a href="/wiki/Central_processing_unit" title="Central processing unit">CPU</a> family </td> <td><code>NOP</code> </td> <td>1 </td> <td>0x90<sup id="cite_ref-x86-instruction-set-intel_2-0" class="reference"><a href="#cite_note-x86-instruction-set-intel-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </td> <td>0x90 is the one-byte encoding for <code>XCHG AX,AX</code> in 16-bit code and <code>XCHG EAX,EAX</code> in 32-bit code. In long mode, <code>XCHG RAX,RAX</code> requires two bytes, as it would begin with an <code>REX.W</code> prefix, making the encoding 0x48 0x90. However, 0x90 is interpreted as a <code>NOP</code> in long mode regardless of whether it is preceded by 0x48.<sup id="cite_ref-x86-instruction-set-intel_2-1" class="reference"><a href="#cite_note-x86-instruction-set-intel-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td>multi-byte <code>NOP</code> </td> <td>2–9 for <a href="/wiki/Pentium_Pro" title="Pentium Pro">Pentium Pro</a> and later Intel processors, and all AMD AMD64 processors </td> <td>0x66 0x90<br /> <p>0x0F 0x1F 0x00<br /> </p><p>0x0F 0x1F 0x40 0x00<br /> </p><p>0x0F 0x1F 0x44 0x00 0x00<br /> </p><p>0x66 0x0F 0x1F 0x44 0x00 0x00<br /> </p><p>0x0F 0x1F 0x80 0x00 0x00 0x00 0x00<br /> </p><p>0x0F 0x1F 0x84 0x00 0x00 0x00 0x00 0x00<br /> </p><p>0x66 0x0F 0x1F 0x84 0x00 0x00 0x00 0x00 0x00<sup id="cite_ref-x86-instruction-set-intel_2-2" class="reference"><a href="#cite_note-x86-instruction-set-intel-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p> </td> <td>0x66 is the operand-size override prefix. <p>0x0F 0x1F is a two-byte NOP opcode that takes a <a href="/wiki/ModR/M" title="ModR/M">ModR/M</a> operand upon which no operation is performed. Operands added to this are: </p><p>0x00 is <code>[EAX]</code> </p><p>0x40 0x00 is <code>[EAX + 00H]</code> </p><p>0x44 0x00 0x00 is <code>[EAX + EAX*1 + 00H]</code> </p><p>0x80 0x00 0x00 0x00 0x00 is <code>[EAX + 00000000H]</code> </p><p>0x84 0x00 0x00 0x00 0x00 0x00 is <code>[EAX + EAX*1 + 00000000H]</code>.<sup id="cite_ref-x86-instruction-set-intel_2-3" class="reference"><a href="#cite_note-x86-instruction-set-intel-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p> </td></tr> <tr> <td><a href="/wiki/Intel_8008" title="Intel 8008">Intel 8008</a> </td> <td><code>LAA</code> </td> <td>1 </td> <td>0xC0 </td> <td>Load A from A </td></tr> <tr> <td><a href="/wiki/Intel" title="Intel">Intel</a> <a href="/wiki/8051" class="mw-redirect" title="8051">8051</a> / <a href="/wiki/MCS-51" class="mw-redirect" title="MCS-51">MCS-51</a> family </td> <td><code>NOP</code> </td> <td>1 </td> <td>0x00 </td> <td> </td></tr> <tr> <td><a href="/wiki/Intel_8080" title="Intel 8080">Intel 8080</a>, <a href="/wiki/Intel_8085" title="Intel 8085">Intel 8085</a>, <a href="/wiki/Z80" class="mw-redirect" title="Z80">Z80</a> </td> <td><code>NOP</code> </td> <td>1 </td> <td>0x00 </td> <td> </td></tr> <tr> <td rowspan="2"><a href="/wiki/Intel_i860" title="Intel i860">Intel i860</a> </td> <td><code>NOP</code> </td> <td>4 </td> <td>0xA0000000 </td> <td>Core no-operation. Opcode for <span class="nowrap"><code>shl r0,r0,r0</code>,</span> an instruction to left-shift the all-0s register by itself.<sup id="cite_ref-i860_3-0" class="reference"><a href="#cite_note-i860-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td><code>FNOP</code> </td> <td>4 </td> <td>0xB0000000 </td> <td>Floating-point no-operation. Opcode for <span class="nowrap"><code>shrd r0,r0,r0</code></span>, a shift-right-double instruction that takes the all-0s register as input and output.<sup id="cite_ref-i860_3-1" class="reference"><a href="#cite_note-i860-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td rowspan="5"><a href="/wiki/Intel" title="Intel">Intel</a> <a href="/wiki/IA-64" title="IA-64">IA-64</a> (<a href="/wiki/Itanium" title="Itanium">Itanium</a>) </td> <td><code>(qp) NOP.b imm21</code> </td> <td>41 bits </td> <td>0x04000000000 </td> <td rowspan="5">On IA-64, the <code>NOP</code> instruction has five forms, each of which can be executed only on a particular execution unit type.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> <p>All five <code>NOP</code> forms include a 6-bit qp field (bits 5:0) and a 21-bit immediate field (bit 36 + bits 25:6). These fields may be set to any value with no effect on the operation of the instruction. (The encodings listed here result from setting these fields to all-0s - which is common but not required). </p><p>The <code>NOP.x</code> form of the instruction additionally consumes a second 41-bit instruction slot - the contents of this slot is considered to be providing 41 additional immediate-bits, for a total immediate-size of 62 bits. </p> </td></tr> <tr> <td><code>(qp) NOP.f imm21</code> </td> <td rowspan="3">41 bits </td> <td rowspan="3">0x00008000000 </td></tr> <tr> <td><code>(qp) NOP.i imm21</code> </td></tr> <tr> <td><code>(qp) NOP.m imm21</code> </td></tr> <tr> <td><span class="nowrap"><code>(qp) NOP.x imm62</code></span> </td> <td>41+41 bits </td> <td>0x00008000000 imm41 </td></tr> <tr> <th colspan="5"> </th></tr> <tr> <td rowspan="4"><a href="/wiki/ARM_architecture" class="mw-redirect" title="ARM architecture">ARM A32</a> </td> <td><code>NOP</code></td> <td>4</td> <td>0x*320F000 </td> <td>Architectural ARM A32 NOP ("true" nop, with no register dependencies). Introduced with ARMv6K (<a href="/wiki/ARM_11" class="mw-redirect" title="ARM 11">ARM 11</a>76, released in 2003), and present in all later ARM A32 processors. (The * indicates a 4-bit field that may take any value other than 0xF.)<sup id="cite_ref-arm_ddi_0406_5-0" class="reference"><a href="#cite_note-arm_ddi_0406-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td><code>MOV r0,r0</code>/<code>NOP</code></td> <td>4</td> <td>0xE1A00000 </td> <td>Recommended A32 no-operation encoding for older 32-bit ARM processors that pre-date ARMv6K. Assemblers for A32 will usually output this opcode when given the "NOP" mnemonic unless they are told to target ARMv6K or later versions of the ARM architecture.<sup id="cite_ref-arm_dui_0041c_6-0" class="reference"><a href="#cite_note-arm_dui_0041c-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-arm_asmref_7-0" class="reference"><a href="#cite_note-arm_asmref-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td><code>ANDEQ r0,r0,r0</code></td> <td>4</td> <td>0x00000000 </td> <td>Bitwise-AND r0 with itself if equal. Commonly used no-op encoding due to the simplicity of its encoding.<sup id="cite_ref-osmith96_8-0" class="reference"><a href="#cite_note-osmith96-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td><code>MOVNV r0,r0</code></td> <td>4</td> <td>0xF1A00000 </td> <td>Move r0 to itself never. Obsolete no-op encoding that used to be recommended for the ARM2/ARM3 processors in older <a href="/wiki/Acorn_Archimedes" title="Acorn Archimedes">Acorn Archimedes</a> computers.<sup id="cite_ref-osmith96_8-1" class="reference"><a href="#cite_note-osmith96-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> Makes use of the NV ("never") condition code — which has been deprecated since 1993,<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> with support fully removed with ARMv5.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td rowspan="3"><a href="/wiki/ARM_architecture#Thumb-2" class="mw-redirect" title="ARM architecture">ARM T32</a> (Thumb) </td> <td><code>NOP</code></td> <td>2</td> <td>0xBF00 </td> <td rowspan="2">Architectural ARM T32 (Thumb-2) NOPs ("true" nops, with no register dependencies). Introduced with ARMv6T2 (<a href="/wiki/ARM_11" class="mw-redirect" title="ARM 11">ARM 11</a>56, released in 2003), and present in all later ARM T32 processors.<sup id="cite_ref-arm_ddi_0406_5-1" class="reference"><a href="#cite_note-arm_ddi_0406-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td><code>NOP.W</code></td> <td>4</td> <td>0xF3AF8000 </td></tr> <tr> <td><code>MOV r8,r8</code>/<code>NOP</code></td> <td>2</td> <td>0x46C0 </td> <td>Recommended Thumb no-operation encoding for older 32-bit Thumb processors that pre-date ARMv6T2. Assemblers for T32 will usually output this opcode when given the "NOP" mnemonic unless they are told to target ARMv6T2 or later versions of the ARM Thumb architecture.<sup id="cite_ref-arm_dui_0041c_6-1" class="reference"><a href="#cite_note-arm_dui_0041c-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-arm_asmref_7-1" class="reference"><a href="#cite_note-arm_asmref-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td><a href="/wiki/ARM_architecture#ARMv8_and_64-bit" class="mw-redirect" title="ARM architecture">ARM A64</a> (64 bit) </td> <td><code>NOP</code> </td> <td>4 </td> <td>0xD503201F </td> <td>Architectural NOP. </td></tr> <tr> <th colspan="5"> </th></tr> <tr> <td><a href="/wiki/DEC_Alpha" title="DEC Alpha">DEC Alpha</a> </td> <td><code>NOP</code> </td> <td>4 </td> <td>0x47FF041F </td> <td>Opcode for <code>BIS r31,r31,r31</code>, an instruction that bitwise-ORs the always-0 register with itself. </td></tr> <tr> <td><a href="/wiki/AMD_29k" class="mw-redirect" title="AMD 29k">AMD 29k</a> </td> <td><code>NOP</code> </td> <td>4 </td> <td>0x70400101 </td> <td>Opcode for <code>aseq 0x40,gr1,gr1</code>, an instruction that asserts that the <a href="/wiki/Stack_register" title="Stack register">stack register</a> is equal to itself.<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td><a href="/wiki/AVR_microcontrollers" title="AVR microcontrollers">AVR</a> </td> <td><code>NOP</code> </td> <td>2 </td> <td>0x0000 </td> <td>one clock cycle </td></tr> <tr> <td rowspan="2"><span class="nowrap"><a href="/wiki/IBM_System/360" title="IBM System/360">IBM System/360</a>,</span> <span class="nowrap"><a href="/wiki/IBM_System/370" title="IBM System/370">IBM System/370</a>,</span> <span class="nowrap"><a href="/wiki/IBM_System/390" title="IBM System/390">IBM System/390</a>,</span> <span class="nowrap"><a href="/wiki/Z/Architecture" title="Z/Architecture">z/Architecture</a>,</span> <span class="nowrap"><a href="/wiki/UNIVAC_Series_90" title="UNIVAC Series 90">UNIVAC Series 90</a></span> </td> <td><code>NOP</code> </td> <td>4 </td> <td>0x47000000 or 0x470nnnnn or 0x47n0nnnn where "n" is any 4-bit value. </td> <td rowspan="2">The NOP ("No-Op") and NOPR ("No-Op Register") are a subset of the "Branch on Condition" or "Branch on Condition Register" instructions, respectively; both versions have two options for generating a NO-OP. <p>In the case of both the NOP and NOPR instructions, the first 0 in the second byte is the "mask" value, the condition to test such as equal, not equal, high, low, etc. If the mask is 0, no branch occurs. </p><p>In the case of the NOPR instruction, the second value in the second byte is the register to branch on. If register 0 is chosen, no branch occurs regardless of the mask value. Thus, if either of the two values in the second byte is 0, the branch will not happen. If the first 0 in the second byte is 0, the value of the second value in the second byte is irrelevant on most processors; however, on the <a href="/wiki/IBM_System/360_Model_91" title="IBM System/360 Model 91">IBM System/360 Model 91</a>, if that value refers to register 15, the instruction will wait for all previously-decoded instructions to complete before continuing.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p><p>In the case of the NOP instruction, the second value in the second byte is the "base" register of a combined base register, displacement register and offset address. If the base register is also 0, the branch is not taken regardless of the value of the displacement register or displacement address. </p> </td></tr> <tr> <td><code>NOPR</code> </td> <td>2 </td> <td>0x0700 or 0x070n or 0x07n0 where "n" is any 4-bit value. </td></tr> <tr> <td><a href="/wiki/LoongArch" class="mw-redirect" title="LoongArch">LoongArch</a> </td> <td><code>NOP</code> </td> <td>4 </td> <td>0x03400000 </td> <td>Opcode for <code>andi r0,r0,0</code>, an instruction that bitwise-ANDs the always-0 register with zero.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td><a href="/wiki/MIPS_architecture" title="MIPS architecture">MIPS</a> </td> <td><code>NOP</code> </td> <td>4 </td> <td>0x00000000 </td> <td>Stands for <code>sll r0,r0,0</code>, meaning: Logically shift register 0 zero bits to the left and store the result in register 0. Writes to register 0 are ignored; it always contains 0. </td></tr> <tr> <td><a href="/wiki/MIPS-X" title="MIPS-X">MIPS-X</a> </td> <td><code>NOP</code> </td> <td>4 </td> <td>0x60000019 </td> <td>(extended opcode for <code>add r0,r0,r0</code>) </td></tr> <tr> <td><a href="/wiki/MIX_(abstract_machine)" title="MIX (abstract machine)">MIX</a> </td> <td><code>NOP</code> </td> <td>1 word </td> <td>± * * * * 0 </td> <td>The * bytes are arbitrary, and can be anything from 0 to the maximum byte (required to be in the range 63-99). MIX uses sign-magnitude representation. </td></tr> <tr> <td><a href="/wiki/MMIX" title="MMIX">MMIX</a> </td> <td><code>SWYM</code> </td> <td>4 </td> <td>0xFD****** </td> <td>SWYM stands for "Sympathize with your machinery". The * digits can be chosen arbitrarily. </td></tr> <tr> <td><a href="/wiki/MOS_Technology_65xx" class="mw-redirect" title="MOS Technology 65xx">MOS Technology 65xx</a> (e.g. <a href="/wiki/6502" class="mw-redirect" title="6502">6502</a>) </td> <td><code>NOP</code> </td> <td>1 </td> <td>0xEA </td> <td><code><b>NOP</b></code> consumes two clock cycles. <a href="/wiki/Illegal_opcode" title="Illegal opcode">Undefined opcodes</a> in the <a href="/wiki/NMOS_logic" title="NMOS logic">NMOS</a> versions of the 65xx family were converted to be NOPs of varying instruction lengths and cycle times in the <a href="/wiki/WDC_65C02" title="WDC 65C02">65C02</a>. </td></tr> <tr> <td><a href="/wiki/Motorola_6800" title="Motorola 6800">Motorola 6800</a> </td> <td><code>NOP</code> </td> <td>1 </td> <td>0x01 </td> <td> </td></tr> <tr> <td rowspan="2"><a href="/wiki/Motorola_68000_family" class="mw-redirect" title="Motorola 68000 family">Motorola 68000 family</a> </td> <td><code>NOP</code> </td> <td>2 </td> <td>0x4E71 </td> <td>This synchronizes the <a href="/wiki/Pipeline_(computing)" title="Pipeline (computing)">pipeline</a> and prevents instruction overlap.<sup id="cite_ref-m68ref_1-1" class="reference"><a href="#cite_note-m68ref-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page: 3-21">: 3-21 </span></sup><sup id="cite_ref-m68ref_1-2" class="reference"><a href="#cite_note-m68ref-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page: 4-147">: 4-147 </span></sup> </td></tr> <tr> <td><code>TRAPF</code>,<br /><span class="nowrap"><code>TRAPF.W #data</code>,</span><br /><code>TRAPF.L #data</code> </td> <td>2,<br />4,<br />6 </td> <td>0x51FC,<br /><span class="nowrap">0x51FA 0xnnnn,</span><br /><span class="nowrap">0x51FB 0xnnnn 0xnnnn</span> </td> <td>Trap if false. <p>Suggested opcode for <a href="/wiki/Motorola_68020" title="Motorola 68020">68020</a> and later 68k processors if a NOP without pipeline synchronization is desired. ('n' may take any 4-bit value.)<sup id="cite_ref-m68ref_1-3" class="reference"><a href="#cite_note-m68ref-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page: 3-21">: 3-21 </span></sup><sup id="cite_ref-m68ref_1-4" class="reference"><a href="#cite_note-m68ref-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page: 4-189">: 4-189 </span></sup> </p> </td></tr> <tr> <td><a href="/wiki/Motorola_6809" title="Motorola 6809">Motorola 6809</a> </td> <td><code>NOP</code> </td> <td>1 </td> <td>0x12 </td> <td> </td></tr> <tr> <td><a href="/wiki/MSP430" class="mw-redirect" title="MSP430">MSP430</a> </td> <td><code>NOP</code> </td> <td>2 </td> <td>0x4303 </td> <td>Opcode for <code>mov #0,r3</code> or <code>mov r3,r3</code>, an instruction that performs a move from a "constant generation register" to itself.<sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td rowspan="2"><a href="/wiki/PA-RISC" title="PA-RISC">PA-RISC</a> </td> <td><code>NOP</code> </td> <td>4 </td> <td>0x08000240 </td> <td>Opcode for <code>OR 0,0,0</code>.<sup id="cite_ref-parisc_nop_16-0" class="reference"><a href="#cite_note-parisc_nop-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td><code>LDI 26,0</code> </td> <td>4 </td> <td>0x34000034 </td> <td>Palindromic NOP - that is, an instruction that executes as NOP regardless of whether byte order is interpreted as <a href="/wiki/Endianness" title="Endianness">little-endian or big-endian</a>. Some PA-RISC system instructions are required to be followed by seven palindromic NOPs.<sup id="cite_ref-parisc_nop_16-1" class="reference"><a href="#cite_note-parisc_nop-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td><a href="/wiki/PDP-10" title="PDP-10">PDP-10</a> </td> <td><code>JFCL 0,</code> (conventional)<br /><code>JUMP, SETA, SETAI, CAI, TRN, TLN</code> </td> <td>1 word </td> <td>25500******* (octal) </td> <td>Jump never<br />Jump never, set nothing, skip never </td></tr> <tr> <td><a href="/wiki/PDP-11_architecture" title="PDP-11 architecture">PDP-11</a> </td> <td><code>NOP</code> </td> <td>2 </td> <td>000240 (octal) </td> <td>Clear none of the condition codes </td></tr> <tr> <td><a href="/wiki/PIC_microcontroller" class="mw-redirect" title="PIC microcontroller">PIC microcontroller</a> </td> <td><code>NOP</code> </td> <td>12 bits </td> <td>0b000000000000 </td> <td> </td></tr> <tr> <td><a href="/wiki/IBM_POWER_architecture" title="IBM POWER architecture">POWER</a>, <a href="/wiki/PowerPC" title="PowerPC">PowerPC</a>, <a href="/wiki/Power_ISA" title="Power ISA">Power ISA</a> </td> <td><code>NOP</code> </td> <td>4 </td> <td>0x60000000 </td> <td>Opcode for <code>ori r0,r0,0</code>. <p>Under the Power ISA, many apparent no-op instruction encodings have significant side-effects − therefore, no-op encodings other than <span class="nowrap"><code>ori r0,r0,0</code></span> should be carefully avoided unless these side-effects are specifically intended. For example:<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> </p> <ul><li><code>ori r31,r31,0</code> is a serializing instruction.</li> <li><code>or rX,rX,rX</code> with X=1,2,3,5,6,7 or 31 sets thread priority based on X.</li> <li><code>or r26,r26,r26</code> is a memory store writeback hint.</li> <li><code>xori r0,r0,0</code> is an explicitly unoptimized no-op for use in timing-loops.</li> <li><code>and rX,rX,rX</code> with X=0,1 are performance-probe no-ops.</li> <li><code>or rX,rX,rX</code> with X=28,29,30,31 will stall instruction dispatch for a fixed number of CPU cycles on IBM <a href="/wiki/Power_Processing_Element" title="Power Processing Element">PPE</a> based processors.<sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup></li> <li><code> ori rX,rX,0</code> with X=1,2 are "group ending NOP"s in some <a href="/wiki/IBM_Power_microprocessors" title="IBM Power microprocessors">POWER CPUs</a><sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup></li></ul> </td></tr> <tr> <td rowspan="2"><a href="/wiki/RISC-V" title="RISC-V">RISC-V</a> </td> <td><code>NOP</code> </td> <td>4 </td> <td>0x00000013 </td> <td><code>ADDI x0, x0, 0</code> </td></tr> <tr> <td><code>C.NOP</code> </td> <td>2 </td> <td>0x0001 </td> <td><code>C.ADDI x0, 0</code>. Only available on RISC-V CPUs that support the "C" (compressed instructions) extension.<sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td><a href="/wiki/Signetics_8X300" title="Signetics 8X300">Signetics 8X300</a> </td> <td><code>MOV AUX, AUX</code> </td> <td>16 bits </td> <td>0x0000 </td> <td>Move AUX to AUX with no rotate </td></tr> <tr> <td><a href="/wiki/SPARC" title="SPARC">SPARC</a> </td> <td><code>NOP</code> </td> <td>4 </td> <td>0x01000000 </td> <td>Stands for <code>sethi 0, %g0</code> which zeroes the hardwired-to-zero <code>%g0</code> register<sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td rowspan="2"><a href="/wiki/SuperH" title="SuperH">SuperH</a> </td> <td><code>NOP</code> </td> <td>2 </td> <td>0x0009 </td> <td><sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td><code>NOP</code> </td> <td>4 </td> <td>0x6FF0FFF0 </td> <td>32-bit NOP, present on SH-5 only.<sup id="cite_ref-24" class="reference"><a href="#cite_note-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td rowspan="2"><a href="/wiki/Tensilica" title="Tensilica">Tensilica</a> Xtensa </td> <td><code>NOP</code>, <code>_NOP</code> </td> <td>3 </td> <td>0x0020F0 </td> <td>Assemblers may convert "NOP" to "NOP.N" - the "_NOP" mnemonic (with a leading underscore) can be used to prevent such conversion.<sup id="cite_ref-25" class="reference"><a href="#cite_note-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td><code>NOP.N</code> </td> <td>2 </td> <td>0xF03D </td> <td> </td></tr> <tr> <td><a href="/wiki/VAX" title="VAX">VAX</a> </td> <td><code>NOP</code> </td> <td>1 </td> <td>0x01 </td> <td>Delay is dependent on processor type </td></tr> <tr> <td><a href="/wiki/WD16" title="WD16">WD16</a> </td> <td><code>NOP</code> </td> <td>2 </td> <td>0x0000 </td> <td> </td></tr></tbody></table> <p>From a hardware design point of view, unmapped areas of a bus are often designed to return zeroes; since the <a href="/wiki/NOP_slide" title="NOP slide">NOP slide</a> behavior is often desirable, it gives a bias to coding it with the all-zeroes opcode. </p> <div class="mw-heading mw-heading2"><h2 id="Code">Code</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=NOP_(code)&action=edit&section=2" title="Edit section: Code"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A function or a sequence of programming language statements is a NOP or null statement if it has no effect. Null statements may be required by the <a href="/wiki/Programming_language_syntax" class="mw-redirect" title="Programming language syntax">syntax</a> of some languages in certain contexts. </p> <div class="mw-heading mw-heading3"><h3 id="Ada">Ada</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=NOP_(code)&action=edit&section=3" title="Edit section: Ada"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In <a href="/wiki/Ada_(programming_language)" title="Ada (programming language)">Ada</a>, the <code>null</code> statement serves as a NOP.<sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> As the syntax forbids that control statements or functions be empty, the <code>null</code> statement must be used to specify that no action is required. (Thus, if the programmer forgets to write a sequence of statements, the program will fail to compile.) </p> <div class="mw-heading mw-heading3"><h3 id="C_and_derivatives">C and derivatives</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=NOP_(code)&action=edit&section=4" title="Edit section: C and derivatives"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The simplest NOP statement in C is the <i>null statement</i>, which is just a semi-colon in a context requiring a statement. </p><p>Most C compilers generate no code for null statements, which has historical and performance reasons. </p> <pre>  ; </pre> <p>An empty block (compound statement) is also a NOP, and may be more legible, but will still have no code generated for it by the compiler. </p> <pre> {} </pre> <p>In some cases, such as the body of a function, a block must be used, but this can be empty. In C, statements cannot be empty—simple statements must end with a <code>;</code> (semicolon) while compound statements are enclosed in <code>{}</code> (braces), which does not itself need a following semicolon. Thus in contexts where a statement is grammatically required, some such null statement can be used. </p><p>The null statement is useless by itself, but it can have a syntactic use in a wider context, e.g., within the context of a loop: </p> <div class="mw-highlight mw-highlight-lang-c mw-content-ltr" dir="ltr"><pre><span></span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">getchar</span><span class="p">()</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="sc">'\n'</span><span class="p">)</span><span class="w"> </span><span class="p">{}</span> </pre></div> <p>alternatively, </p> <div class="mw-highlight mw-highlight-lang-c mw-content-ltr" dir="ltr"><pre><span></span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">getchar</span><span class="p">()</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="sc">'\n'</span><span class="p">)</span> <span class="w"> </span><span class="p">;</span> </pre></div> <p>or more tersely: </p> <div class="mw-highlight mw-highlight-lang-c mw-content-ltr" dir="ltr"><pre><span></span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">getchar</span><span class="p">()</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="sc">'\n'</span><span class="p">);</span> </pre></div> <p>(note that the last form may be confusing, and as such generates a warning with some compilers or compiler options, as semicolon usually indicates an end of function call instruction when placed after a parenthesis on the end of line). </p><p>The above code continues calling the function <code>getchar()</code> until it returns a <code>\n</code> (newline) character, essentially fast-forwarding the current reading location of standard input to the beginning of next line. </p> <div class="mw-heading mw-heading3"><h3 id="Fortran">Fortran</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=NOP_(code)&action=edit&section=5" title="Edit section: Fortran"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In <a href="/wiki/Fortran" title="Fortran">Fortran</a>, the <code>CONTINUE</code> statement is used in some contexts such as the last statement in a DO loop, although it can be used anywhere, and does not have any functionality. </p> <div class="mw-heading mw-heading3"><h3 id="JavaScript">JavaScript</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=NOP_(code)&action=edit&section=6" title="Edit section: JavaScript"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <a href="/wiki/JavaScript" title="JavaScript">JavaScript</a> language does not have a built-in NOP statement. Many implementations are possible: </p> <ul><li>Use the <code>;</code> <i>empty statement</i><sup id="cite_ref-27" class="reference"><a href="#cite_note-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> or the <code>{}</code> empty <i>block statement</i> the same way as in the <a class="mw-selflink-fragment" href="#C_and_derivatives">C and derivatives</a> examples;</li> <li>Use the <code>undefined</code> or the <code>null</code> expression as a complete statement (an <i>expression statement</i>) when the previous methods are not allowed by the syntax.</li></ul> <p>Alternatives, in situations where a function is required, are: </p> <ul><li>Use the <code>Function.prototype()</code> built-in function, that accepts any arguments and returns <code>undefined</code>;<sup id="cite_ref-28" class="reference"><a href="#cite_note-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup></li> <li>Use a NOP function available in a third-party library —see below;</li> <li>Define a custom NOP function, as in the following example (using the <a href="/wiki/ES6" class="mw-redirect" title="ES6">ES6</a> arrow function syntax):</li></ul> <div class="mw-highlight mw-highlight-lang-javascript mw-content-ltr" dir="ltr"><pre><span></span><span class="kd">const</span><span class="w"> </span><span class="nx">noop</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">()</span><span class="w"> </span><span class="p">=></span><span class="w"> </span><span class="p">{};</span> </pre></div> <div class="mw-heading mw-heading4"><h4 id="AngularJS">AngularJS</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=NOP_(code)&action=edit&section=7" title="Edit section: AngularJS"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <a href="/wiki/AngularJS" title="AngularJS">AngularJS</a> framework provides <a rel="nofollow" class="external text" href="https://docs.angularjs.org/api/ng/function/angular.noop">angular.noop</a> function that performs no operations. </p> <div class="mw-heading mw-heading4"><h4 id="jQuery">jQuery</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=NOP_(code)&action=edit&section=8" title="Edit section: jQuery"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <a href="/wiki/JQuery" title="JQuery">jQuery</a> library provides a function <code>jQuery.noop()</code>, which does nothing.<sup id="cite_ref-29" class="reference"><a href="#cite_note-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading4"><h4 id="Lodash">Lodash</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=NOP_(code)&action=edit&section=9" title="Edit section: Lodash"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <a href="/wiki/Lodash" title="Lodash">Lodash</a> library provides a function <code>_.noop()</code>, which returns undefined and does nothing.<sup id="cite_ref-30" class="reference"><a href="#cite_note-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Pascal">Pascal</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=NOP_(code)&action=edit&section=10" title="Edit section: Pascal"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>As with C, the ; used by itself can be used as a null statement in <a href="/wiki/Pascal_(programming_language)" title="Pascal (programming language)">Pascal</a>. In fact, due to the specification of the language, in a BEGIN / END block, the semicolon is optional before the END statement, thus a semicolon used there is superfluous. </p><p>Also, a block consisting of <code> BEGIN END;</code> may be used as a placeholder to indicate no action, even if placed inside another BEGIN / END block. </p> <div class="mw-heading mw-heading3"><h3 id="Python">Python</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=NOP_(code)&action=edit&section=11" title="Edit section: Python"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <a href="/wiki/Python_(programming_language)" title="Python (programming language)">Python</a> programming language has a <a href="/wiki/Python_(programming_language)#Statements_and_control_flow" title="Python (programming language)"><code>pass</code> statement</a> which has no effect when executed and thus serves as a NOP. It is primarily used to ensure correct syntax due to Python's <a href="/wiki/Off-side_rule" title="Off-side rule">indentation-sensitive syntax</a>; for example the syntax for definition of a <a href="/wiki/Class_(computer_programming)" title="Class (computer programming)">class</a> requires an indented block with the class logic, which has to be expressed as <code>pass</code> when it should be empty. </p> <div class="mw-heading mw-heading3"><h3 id="Shell_scripting_(bash,_zsh,_etc.)"><span id="Shell_scripting_.28bash.2C_zsh.2C_etc..29"></span>Shell scripting (bash, zsh, etc.)</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=NOP_(code)&action=edit&section=12" title="Edit section: Shell scripting (bash, zsh, etc.)"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The '<code>:</code>' [colon] command is a shell builtin that has similar effect to a "NOP" (a do-nothing operation). It is not technically an NOP, as it changes the special parameter $? (exit status of last command) to 0. It may be considered a synonym for the shell builtin 'true', and its exit status is true (0).<sup id="cite_ref-31" class="reference"><a href="#cite_note-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-32" class="reference"><a href="#cite_note-32"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-33" class="reference"><a href="#cite_note-33"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="TeX_macro_language_(ConTeXt,_LaTeX,_etc.)"><span id="TeX_macro_language_.28ConTeXt.2C_LaTeX.2C_etc..29"></span>TeX macro language (ConTeXt, LaTeX, etc.)</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=NOP_(code)&action=edit&section=13" title="Edit section: TeX macro language (ConTeXt, LaTeX, etc.)"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <a href="/wiki/TeX" title="TeX">TeX</a> typographical system's macro language has the <code>\relax</code> command.<sup id="cite_ref-34" class="reference"><a href="#cite_note-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> It does nothing by itself, but may be used to prevent the immediately preceding command from parsing any subsequent tokens.<sup id="cite_ref-35" class="reference"><a href="#cite_note-35"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="NOP_protocol_commands">NOP protocol commands</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=NOP_(code)&action=edit&section=14" title="Edit section: NOP protocol commands"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Many <a href="/wiki/Protocol_(computing)" class="mw-redirect" title="Protocol (computing)">computer protocols</a>, such as <a href="/wiki/Telnet" title="Telnet">telnet</a>, include a NOP command that a client can issue to request a response from the server without requesting any other actions. Such a command can be used to <a href="/wiki/Keepalive" title="Keepalive">ensure the connection is still alive</a> or that the server is responsive. A NOOP command is part of the following protocols (<i>this is a partial list</i>): </p> <ul><li><a href="/wiki/Telnet" title="Telnet">telnet</a></li> <li><a href="/wiki/File_Transfer_Protocol" title="File Transfer Protocol">FTP</a></li> <li><a href="/wiki/Simple_Mail_Transfer_Protocol" title="Simple Mail Transfer Protocol">SMTP</a></li> <li><a href="/wiki/X_Window_core_protocol" class="mw-redirect" title="X Window core protocol">X11</a></li> <li><a href="/wiki/Post_Office_Protocol" title="Post Office Protocol">POP3</a></li> <li><a href="/wiki/Network_News_Transfer_Protocol" title="Network News Transfer Protocol">NNTP</a></li> <li><a href="/wiki/Finger_protocol" class="mw-redirect" title="Finger protocol">finger</a></li> <li><a href="/wiki/Internet_Message_Access_Protocol" title="Internet Message Access Protocol">IMAP4</a></li> <li><a href="/wiki/BitTorrent_(protocol)" class="mw-redirect" title="BitTorrent (protocol)">BitTorrent</a></li></ul> <p>Note that unlike the other protocols listed, the IMAP4 NOOP command has a specific purpose—it allows the server to send any pending notifications to the client. </p><p>While most <a href="/wiki/Telnet" title="Telnet">telnet</a> or <a href="/wiki/FTP" class="mw-redirect" title="FTP">FTP</a> servers respond to a NOOP command with "OK" or "+OK", some programmers have added quirky responses to the client. For example, the <code>ftpd</code> daemon of <a href="/wiki/MINIX" class="mw-redirect" title="MINIX">MINIX</a> responds to NOOP with the message:<sup id="cite_ref-minix_ftpd_36-0" class="reference"><a href="#cite_note-minix_ftpd-36"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup> </p> <pre><a href="/wiki/List_of_FTP_server_return_codes" title="List of FTP server return codes">200</a> NOOP to you too! </pre> <div class="mw-heading mw-heading2"><h2 id="Cracking">Cracking</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=NOP_(code)&action=edit&section=15" title="Edit section: Cracking"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>NOPs are often involved when <a href="/wiki/Software_cracking" title="Software cracking">cracking</a> software that checks for serial numbers, specific hardware or software requirements, presence or absence of hardware <a href="/wiki/Dongle" title="Dongle">dongles</a>, etc. in the form of a <a href="/wiki/NOP_slide" title="NOP slide">NOP slide</a>. This process is accomplished by altering <a href="/wiki/Subroutine" class="mw-redirect" title="Subroutine">functions and subroutines</a> to bypass security checks and instead simply return the expected value being checked for. Because most of the instructions in the security check routine will be unused, these would be replaced with NOPs, thus removing the software's security functionality without altering the positioning of everything which follows in the binary. </p> <div class="mw-heading mw-heading2"><h2 id="Security_exploits">Security exploits</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=NOP_(code)&action=edit&section=16" title="Edit section: Security exploits"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The NOP opcode can be used to form a <a href="/wiki/NOP_slide" title="NOP slide">NOP slide</a>, which allows code to execute when the exact value of the instruction pointer is indeterminate (e.g., when a buffer overflow causes a function's return address on the stack to be overwritten). </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=NOP_(code)&action=edit&section=17" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Comment_(computer_programming)" title="Comment (computer programming)">Comment (computer programming)</a> – annotations generally for programmers that are ignored by compilers and interpreters</li> <li><a href="/wiki/Computer_architecture" title="Computer architecture">Computer architecture</a></li> <li><a href="/wiki/Filler_text" title="Filler text">Filler text</a></li> <li><a href="/wiki/Halt_and_Catch_Fire_(computing)" title="Halt and Catch Fire (computing)">Halt and Catch Fire</a> – also pauses the CPU</li> <li><a href="/wiki/HLT_(x86_instruction)" title="HLT (x86 instruction)">HLT (x86 instruction)</a> – pauses the CPU</li> <li><a href="/wiki/Identity_function" title="Identity function">Identity function</a> – the functional programming equivalent to NOP</li> <li><a href="/wiki/IEFBR14" title="IEFBR14">IEFBR14</a> – mainframe tautology</li> <li><a href="/wiki/Xyzzy_(computing)" title="Xyzzy (computing)">xyzzy (computing)</a> – a command sometimes used instead of NOP</li> <li><a href="/wiki/X86_instruction_listings#Added_in_P5/P6-class_processors" title="X86 instruction listings">X86 instruction listings#Added in P5/P6-class processors</a> - <code>NOPL</code>, the official long <code>NOP</code></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=NOP_(code)&action=edit&section=18" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-m68ref-1"><span class="mw-cite-backlink">^ <a href="#cite_ref-m68ref_1-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-m68ref_1-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-m68ref_1-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-m68ref_1-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-m68ref_1-4"><sup><i><b>e</b></i></sup></a></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.nxp.com/docs/en/reference-manual/M68000PRM.pdf">"Motorola 68000 Programmer's Reference Manual"</a> <span class="cs1-format">(PDF)</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Motorola+68000+Programmer%27s+Reference+Manual&rft_id=https%3A%2F%2Fwww.nxp.com%2Fdocs%2Fen%2Freference-manual%2FM68000PRM.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3ANOP+%28code%29" class="Z3988"></span></span> </li> <li id="cite_note-x86-instruction-set-intel-2"><span class="mw-cite-backlink">^ <a href="#cite_ref-x86-instruction-set-intel_2-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-x86-instruction-set-intel_2-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-x86-instruction-set-intel_2-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-x86-instruction-set-intel_2-3"><sup><i><b>d</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.intel.com/content/www/us/en/developer/articles/technical/intel-sdm.html">"Intel 64 and IA-32 Architectures Software Developer's Manual: Instruction Set Reference A-Z"</a><span class="reference-accessdate">. Retrieved <span class="nowrap">2012-03-01</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Intel+64+and+IA-32+Architectures+Software+Developer%27s+Manual%3A+Instruction+Set+Reference+A-Z&rft_id=https%3A%2F%2Fwww.intel.com%2Fcontent%2Fwww%2Fus%2Fen%2Fdeveloper%2Farticles%2Ftechnical%2Fintel-sdm.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ANOP+%28code%29" class="Z3988"></span></span> </li> <li id="cite_note-i860-3"><span class="mw-cite-backlink">^ <a href="#cite_ref-i860_3-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-i860_3-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text">Intel, <a rel="nofollow" class="external text" href="https://bitsavers.org/components/intel/i860/240329-002_i860_64-Bit_Microprocessor_Programmers_Reference_Feb89.pdf">i860 64-bit Microprocessor Programmer's Reference Manual</a>, order no. 240329-002, Feb 1989, pages 68 and 172.</span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text">Intel, <a rel="nofollow" class="external text" href="https://www.intel.com/content/dam/doc/manual/itanium-architecture-vol-1-2-3-4-reference-set-manual.pdf">Intel Itanium Architecture Software Developer’s Manual rev 2.3</a>, May 2010. 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"The empty statement is a semicolon (<code>;</code>) indicating that no statement will be executed, even if JavaScript syntax requires one."</span> </li> <li id="cite_note-28"><span class="mw-cite-backlink"><b><a href="#cite_ref-28">^</a></b></span> <span class="reference-text">ECMAScript Language Specification – Edition 5.1 – <a rel="nofollow" class="external text" href="https://www.ecma-international.org/ecma-262/5.1/#sec-15.3.4">Properties of the Function Prototype Object</a></span> </li> <li id="cite_note-29"><span class="mw-cite-backlink"><b><a href="#cite_ref-29">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://api.jquery.com/jquery.noop/">jQuery.noop()</a> from jQuery API documentation</span> </li> <li id="cite_note-30"><span class="mw-cite-backlink"><b><a href="#cite_ref-30">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://lodash.com/docs/#noop">"Lodash Documentation"</a>. <i>lodash.com</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2017-12-15</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=lodash.com&rft.atitle=Lodash+Documentation&rft_id=https%3A%2F%2Flodash.com%2Fdocs%2F%23noop&rfr_id=info%3Asid%2Fen.wikipedia.org%3ANOP+%28code%29" class="Z3988"></span></span> </li> <li id="cite_note-31"><span class="mw-cite-backlink"><b><a href="#cite_ref-31">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://tldp.org/LDP/abs/html/special-chars.html">Advanced Bash-Scripting Guide > Chapter 3. Special Characters</a></span> </li> <li id="cite_note-32"><span class="mw-cite-backlink"><b><a href="#cite_ref-32">^</a></b></span> <span class="reference-text">bash manpage > SHELL BUILTIN COMMANDS</span> </li> <li id="cite_note-33"><span class="mw-cite-backlink"><b><a href="#cite_ref-33">^</a></b></span> <span class="reference-text">zsh manpage (zshbuiltins) > SHELL BUILTIN COMMANDS</span> </li> <li id="cite_note-34"><span class="mw-cite-backlink"><b><a href="#cite_ref-34">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFBausum2002" class="citation book cs1">Bausum, David (2002). "TeX Primitive Control Sequences". <a rel="nofollow" class="external text" href="https://www.tug.org/utilities/plain/cseq.html#relax-rp"><i>TeX Reference Manual</i></a>. Kluwer Academic Publishers<span class="reference-accessdate">. Retrieved <span class="nowrap">1 April</span> 2020</span>. <q>According to The TeXbook, 'TeX does nothing' when it encounters <code>\relax</code>. Actually, <code>\relax</code> may tell TeX, 'This is the end of what you've been doing'.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=TeX+Primitive+Control+Sequences&rft.btitle=TeX+Reference+Manual&rft.pub=Kluwer+Academic+Publishers&rft.date=2002&rft.aulast=Bausum&rft.aufirst=David&rft_id=https%3A%2F%2Fwww.tug.org%2Futilities%2Fplain%2Fcseq.html%23relax-rp&rfr_id=info%3Asid%2Fen.wikipedia.org%3ANOP+%28code%29" class="Z3988"></span></span> </li> <li id="cite_note-35"><span class="mw-cite-backlink"><b><a href="#cite_ref-35">^</a></b></span> <span class="reference-text">TeX wikibook – <a class="external text" href="https://en.wikibooks.org/wiki/TeX/relax">relax</a></span> </li> <li id="cite_note-minix_ftpd-36"><span class="mw-cite-backlink"><b><a href="#cite_ref-minix_ftpd_36-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.cise.ufl.edu/~cop4600/cgi-bin/lxr/http/source.cgi/commands/ftpd/ftpd.c#L139">"ftpd.c"</a><span class="reference-accessdate">. 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