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</a> <ul id="toc-PA1050-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-TOPS-20_capabilities" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#TOPS-20_capabilities"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>TOPS-20 capabilities</span> </div> </a> <button aria-controls="toc-TOPS-20_capabilities-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle TOPS-20 capabilities subsection</span> </button> <ul id="toc-TOPS-20_capabilities-sublist" class="vector-toc-list"> <li id="toc-Command_processor" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Command_processor"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1</span> <span>Command processor</span> </div> </a> <ul id="toc-Command_processor-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Commands" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Commands"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.2</span> <span>Commands</span> </div> </a> <ul id="toc-Commands-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-JSYS_features" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#JSYS_features"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.3</span> <span>JSYS features</span> </div> </a> <ul id="toc-JSYS_features-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-PCL_(Programmable_Command_Language)" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#PCL_(Programmable_Command_Language)"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>PCL (Programmable Command Language)</span> </div> </a> <button 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id="toc-TOPS-20_today-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> <li id="toc-Further_reading" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Further_reading"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>Further reading</span> </div> </a> <ul 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French" lang="fr" hreflang="fr" data-title="TOPS-20" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/TOPS-20" title="TOPS-20 – Italian" lang="it" hreflang="it" data-title="TOPS-20" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-ml mw-list-item"><a href="https://ml.wikipedia.org/wiki/%E0%B4%9F%E0%B5%8B%E0%B4%AA%E0%B5%8D%E0%B4%B8%E0%B5%8D-20" title="ടോപ്സ്-20 – Malayalam" lang="ml" hreflang="ml" data-title="ടോപ്സ്-20" data-language-autonym="മലയാളം" data-language-local-name="Malayalam" class="interlanguage-link-target"><span>മലയാളം</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/TOPS-20" title="TOPS-20 – Dutch" lang="nl" 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<div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Operating system by Digital Equipment Corporation</div> <div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Operating system</div> <style data-mw-deduplicate="TemplateStyles:r1257001546">.mw-parser-output .infobox-subbox{padding:0;border:none;margin:-3px;width:auto;min-width:100%;font-size:100%;clear:none;float:none;background-color:transparent}.mw-parser-output .infobox-3cols-child{margin:auto}.mw-parser-output .infobox .navbar{font-size:100%}@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-full-data:not(.notheme) div:not(.notheme){background:#1f1f23!important;color:#f8f9fa}}@media(min-width:640px){body.skin--responsive .mw-parser-output .infobox-table{display:table!important}body.skin--responsive .mw-parser-output .infobox-table>caption{display:table-caption!important}body.skin--responsive .mw-parser-output .infobox-table>tbody{display:table-row-group}body.skin--responsive .mw-parser-output .infobox-table tr{display:table-row!important}body.skin--responsive .mw-parser-output .infobox-table th,body.skin--responsive .mw-parser-output .infobox-table td{padding-left:inherit;padding-right:inherit}}</style><table class="infobox vevent"><caption class="infobox-title summary">TOPS-20</caption><tbody><tr><td colspan="2" class="infobox-image"><span typeof="mw:File"><a href="/wiki/File:TOPS-20.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/f/f4/TOPS-20.png/300px-TOPS-20.png" decoding="async" width="300" height="139" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/f/f4/TOPS-20.png/450px-TOPS-20.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/f/f4/TOPS-20.png/600px-TOPS-20.png 2x" data-file-width="664" data-file-height="307" /></a></span><div class="infobox-caption">login</div></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="/wiki/Programmer" title="Programmer">Developer</a></th><td class="infobox-data"><a href="/wiki/Digital_Equipment_Corporation" title="Digital Equipment Corporation">Digital Equipment Corporation</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="/wiki/Programming_language" title="Programming language">Written in</a></th><td class="infobox-data"><a href="/wiki/Assembly_language" title="Assembly language">Assembly language</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">OS family</th><td class="infobox-data"><a href="/wiki/TENEX_(operating_system)" title="TENEX (operating system)">TENEX</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Working state</th><td class="infobox-data">Discontinued</td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Initial release</th><td class="infobox-data">1976<span class="noprint">; 48 years ago</span><span style="display:none"> (<span class="bday dtstart published updated">1976</span>)</span></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="/wiki/Software_release_life_cycle" title="Software release life cycle">Latest release</a></th><td class="infobox-data">7.1 / June 1988<span class="noprint">; 36 years ago</span><span style="display:none"> (<span class="bday dtstart published updated">1988-06</span>)</span></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Marketing target</th><td class="infobox-data"><a href="/wiki/Mainframe_computer" title="Mainframe computer">Mainframe computers</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="/wiki/Natural_language" title="Natural language">Available in</a></th><td class="infobox-data"><a href="/wiki/English_language" title="English language">English</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Platforms</th><td class="infobox-data"><a href="/wiki/PDP-10" title="PDP-10">PDP-10</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="/wiki/User_interface" title="User interface">Default<br />user interface</a></th><td class="infobox-data"><a href="/wiki/Command-line_interface" title="Command-line interface">Command-line interface</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="/wiki/Software_license" title="Software license">License</a></th><td class="infobox-data"><a href="/wiki/Proprietary_software" title="Proprietary software">Proprietary</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Preceded by</th><td class="infobox-data"><a href="/wiki/TENEX_(operating_system)" title="TENEX (operating system)">TENEX</a></td></tr></tbody></table> <p>The <b>TOPS-20</b> <a href="/wiki/Operating_system" title="Operating system">operating system</a> by <a href="/wiki/Digital_Equipment_Corporation" title="Digital Equipment Corporation">Digital Equipment Corporation</a> (DEC) is a proprietary<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> OS used on some of DEC's 36-bit <a href="/wiki/Mainframe_computer" title="Mainframe computer">mainframe computers</a>. The Hardware Reference Manual was described as for "DECsystem-10/DECSYSTEM-20 Processor" (meaning the DEC <a href="/wiki/PDP-10" title="PDP-10">PDP-10</a> and the <a href="/wiki/DECSYSTEM-20" title="DECSYSTEM-20">DECSYSTEM-20</a>).<sup id="cite_ref-CMDref_2-0" class="reference"><a href="#cite_note-CMDref-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p><p>TOPS-20 began in 1969 as the <a href="/wiki/TENEX_(operating_system)" title="TENEX (operating system)">TENEX</a> operating system of <a href="/wiki/Bolt,_Beranek_and_Newman" class="mw-redirect" title="Bolt, Beranek and Newman">Bolt, Beranek and Newman</a> (BBN) and shipped as a product by DEC starting in 1976.<sup id="cite_ref-TENXref_3-0" class="reference"><a href="#cite_note-TENXref-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> TOPS-20 is almost entirely unrelated to the similarly named <a href="/wiki/TOPS-10" title="TOPS-10">TOPS-10</a>, but it was shipped with the PA1050 TOPS-10 Monitor Calls emulation facility which allowed most, but not all, TOPS-10 executables to run unchanged. As a matter of policy, DEC did not update PA1050 to support later TOPS-10 additions except where required by DEC software. </p><p>TOPS-20 competed with TOPS-10, <a href="/wiki/Incompatible_Timesharing_System" title="Incompatible Timesharing System">ITS</a><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> and <a href="/wiki/WAITS" title="WAITS">WAITS</a>—all of which were <a href="/wiki/Time-sharing#Notable_time-sharing_systems" title="Time-sharing">notable time-sharing systems</a> for the <a href="/wiki/PDP-10" title="PDP-10">PDP-10</a> during this timeframe. TOPS-20 is informally known as TWENEX.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="TENEX">TENEX</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=TOPS-20&action=edit&section=1" title="Edit section: TENEX"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></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">Main article: <a href="/wiki/TENEX_(operating_system)" title="TENEX (operating system)">TENEX (operating system)</a></div> <p>TOPS-20 was based upon the <a href="/wiki/TENEX_(operating_system)" title="TENEX (operating system)">TENEX</a> operating system, which had been created by <a href="/wiki/BBN_Technologies" class="mw-redirect" title="BBN Technologies">Bolt Beranek and Newman</a> for Digital's <a href="/wiki/PDP-10" title="PDP-10">PDP-10</a> computer. After Digital started development of the KI-10 version of the PDP-10, an issue arose: by this point TENEX was the most popular customer-written PDP-10 operating systems, but it would not run on the new, faster KI-10s. To correct this problem, the DEC PDP-10 sales manager purchased the rights to TENEX from BBN and set up a project to port it to the new machine. In the end, very little of the original TENEX code remained, and Digital ultimately named the resulting operating system TOPS-20. </p> <div class="mw-heading mw-heading2"><h2 id="PA1050">PA1050</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=TOPS-20&action=edit&section=2" title="Edit section: PA1050"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Some of what came with TOPS-20 was merely an emulation of the <a href="/wiki/TOPS-10" title="TOPS-10">TOPS-10</a> Operating System's calls. These were known as UUO's, standing for Unimplemented User Operation,<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> and were needed both for compilers, which were not 20-specific, to run, as well as user-programs written in these languages. The package that was mapped into a user's address space was named PA1050: PA as in PAT as in compatibility; 10 as in DEC or PDP 10; 50 as in a PDP 10 Model 50, 10/50, 1050.<sup id="cite_ref-JSYS104_7-0" class="reference"><a href="#cite_note-JSYS104-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p><p>Sometimes PA1050 was referred to as PAT, a name that was a good fit to the fact that PA1050, "was simply unprivileged user-mode code" that "performed the requested action, using JSYS calls where necessary."<sup id="cite_ref-JSYS104_7-1" class="reference"><a href="#cite_note-JSYS104-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="TOPS-20_capabilities">TOPS-20 capabilities</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=TOPS-20&action=edit&section=3" title="Edit section: TOPS-20 capabilities"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The major ways to get at TOPS-20 capabilities, and what made TOPS-20 important, were </p> <ul><li>Commands entered via the command processor, EXEC.EXE<sup id="cite_ref-CMDref_2-1" class="reference"><a href="#cite_note-CMDref-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup></li> <li>JSYS (Jump to System) calls from MACro-language (.MAC) programs<sup id="cite_ref-8" class="reference"><a href="#cite_note-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></li></ul> <p>The "EXEC" accomplished its work primarily using </p> <ul><li>internal code, including calls via JSYS</li> <li>requesting services from "GALAXY" components (e.g. spoolers)</li></ul> <div class="mw-heading mw-heading3"><h3 id="Command_processor">Command processor</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=TOPS-20&action=edit&section=4" title="Edit section: Command processor"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Rather advanced for its day were some TOPS-20-specific features: </p> <ul><li><a href="/wiki/Command-line_completion" title="Command-line completion">Command completion</a><sup id="cite_ref-TENXref_3-1" class="reference"><a href="#cite_note-TENXref-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup></li> <li>Dynamic help in the form of</li></ul> <dl><dd><ul><li><i>noise-words</i> - typing DIR and then pressing the ESCape key resulted in</li></ul> <dl><dd><dl><dd><dl><dd>DIRectory (of files)</dd></dl></dd></dl></dd> <dd>typing <style data-mw-deduplicate="TemplateStyles:r1249182868">.mw-parser-output .keyboard-key{border:1px solid #aaa;border-radius:0.2em;box-shadow:0.1em 0.1em 0.2em rgba(0,0,0,0.1);background-color:var(--background-color-neutral-subtle,#f8f9fa);background-image:linear-gradient(to bottom,var(--background-color-neutral,#eaecf0),var(--background-color-neutral-subtle,#f8f9fa),var(--background-color-neutral,#eaecf0));color:var(--color-base,#202122);padding:0.1em 0.3em;font-family:inherit;font-size:0.85em}</style><kbd class="keyboard-key nowrap">I</kbd> and pressing the <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1249182868"><kbd class="keyboard-key nowrap">Esc</kbd> key resulted in <dl><dd><dl><dd>Information (about)</dd></dl></dd></dl></dd></dl></dd></dl> <p>One could then type <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1249182868"><kbd class="keyboard-key nowrap">?</kbd> to find out what operands were permitted/required. Pressing <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1249182868"><kbd class="keyboard-key nowrap">Ctrl-T</kbd> displays <a href="/wiki/Status_key" title="Status key">status information</a>. </p> <div class="mw-heading mw-heading3"><h3 id="Commands">Commands</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=TOPS-20&action=edit&section=5" title="Edit section: Commands"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The following list of <a href="/wiki/Command_(computing)" title="Command (computing)">commands</a> are supported by the TOPS-20 Command Processor.<sup id="cite_ref-CMDref_2-2" class="reference"><a href="#cite_note-CMDref-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p> <style data-mw-deduplicate="TemplateStyles:r1184024115">.mw-parser-output .div-col{margin-top:0.3em;column-width:30em}.mw-parser-output .div-col-small{font-size:90%}.mw-parser-output .div-col-rules{column-rule:1px solid #aaa}.mw-parser-output .div-col dl,.mw-parser-output .div-col ol,.mw-parser-output .div-col ul{margin-top:0}.mw-parser-output .div-col li,.mw-parser-output .div-col dd{page-break-inside:avoid;break-inside:avoid-column}</style><div class="div-col" style="column-width: 9em;"> <ul><li>ACCESS</li> <li>ADVISE</li> <li><a href="/wiki/Append" title="Append">APPEND</a></li> <li>ARCHIVE</li> <li>ASSIGN</li> <li>ATTACH</li> <li>BACKSPACE</li> <li>BLANK</li> <li>BREAK</li> <li>BUILD</li> <li>CANCEL</li> <li>CLOSE</li> <li>COMPILE</li> <li>CONNECT</li> <li>CONTINUE</li> <li><a href="/wiki/Copy_(command)" title="Copy (command)">COPY</a></li> <li>CREATE</li> <li>CREF</li> <li>CSAVE</li> <li>DAYTIME</li> <li><a href="/wiki/Dynamic_debugging_technique" title="Dynamic debugging technique">DDT</a></li> <li>DEASSIGN</li> <li><a href="/wiki/Debug_(command)" title="Debug (command)">DEBUG</a></li> <li>DEFINE</li> <li><a href="/wiki/Del_(command)" title="Del (command)">DELETE</a></li> <li>DEPOSIT</li> <li>DETACH</li> <li><a href="/wiki/Dir_(command)" title="Dir (command)">DIRECTORY</a></li> <li>DISABLE</li> <li>DISCARD</li> <li>DISMOUNT</li> <li>EDIT</li> <li>ENABLE</li> <li>END-ACCESS</li> <li>EOF</li> <li>ERUN</li> <li>EXAMINE</li> <li>EXECUTE</li> <li>EXPUNGE</li> <li>FDIRECTORY</li> <li>FORK</li> <li>FREEZE</li> <li>GET</li> <li><a href="/wiki/Help_(command)" title="Help (command)">HELP</a></li> <li>INFORMATION</li> <li>KEEP</li> <li>LOAD</li> <li><a href="/wiki/Login" title="Login">LOGIN</a></li> <li>LOGOUT</li> <li>MERGE</li> <li>MODIFY</li> <li><a href="/wiki/Mount_(computing)" title="Mount (computing)">MOUNT</a></li> <li>PERUSE</li> <li>PLOT</li> <li>POP</li> <li><a href="/wiki/Print_(command)" class="mw-redirect" title="Print (command)">PRINT</a></li> <li>PUNCH</li> <li>PUSH</li> <li>RECEIVE</li> <li>REENTER</li> <li>REFUSE</li> <li><a href="/wiki/Comment_(computer_programming)" title="Comment (computer programming)">REMARK</a></li> <li><a href="/wiki/Ren_(command)" title="Ren (command)">RENAME</a></li> <li>RESET</li> <li>RETRIEVE</li> <li>REWIND</li> <li><a href="/wiki/Run_command" title="Run command">RUN</a></li> <li>SAVE</li> <li>SEND</li> <li>SET</li> <li>SET HOST</li> <li>SKIP</li> <li><a href="/wiki/Start_(command)" title="Start (command)">START</a></li> <li>SUBMIT</li> <li>SYSTAT</li> <li>TAKE</li> <li>TALK</li> <li>TDIRECTORY</li> <li>TERMINAL</li> <li>TRANSLATE</li> <li><a href="/wiki/TYPE_(DOS_command)" title="TYPE (DOS command)">TYPE</a></li> <li>UNATTACH</li> <li><a href="/wiki/Undeletion" title="Undeletion">UNDELETE</a></li> <li>UNKEEP</li> <li>UNLOAD</li> <li>VDIRECTORY</li></ul> </div> <div class="mw-heading mw-heading3"><h3 id="JSYS_features">JSYS features</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=TOPS-20&action=edit&section=6" title="Edit section: JSYS features"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>JSYS stands for <b>J</b>ump to <b>SYS</b>tem.<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> Operands were at times memory addresses. "TOPS-20 allows you to use 18-bit or 30-bit addresses. Some monitor calls require one kind, some the other; some calls accept either kind. Some monitor calls use only 18 bits to hold an address. These calls interpret 18-bit addresses as locations in the current section."<sup id="cite_ref-CMDref_2-3" class="reference"><a href="#cite_note-CMDref-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p><p>Internally, files were first identified, using a GTJFN (Get Job File Number) JSYS, and then that JFN number was used to open (OPENF) and manipulate the file's contents. </p> <div class="mw-heading mw-heading2"><h2 id="PCL_(Programmable_Command_Language)"><span id="PCL_.28Programmable_Command_Language.29"></span>PCL (Programmable Command Language)</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=TOPS-20&action=edit&section=7" title="Edit section: PCL (Programmable Command Language)"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><b>PCL (Programmable Command Language)</b> is a programming language that runs under TOPS-20. PCL source programs are, by default, stored with Filetype .PCL, and enable extending the TOPS-20 EXEC via a verb named DECLARE. Newly compiled commands then become functionally part of the EXEC.<sup id="cite_ref-PCLman_11-0" class="reference"><a href="#cite_note-PCLman-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup><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><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><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> </p> <div class="mw-heading mw-heading3"><h3 id="PCL_language_features">PCL language features</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=TOPS-20&action=edit&section=8" title="Edit section: PCL language features"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>PCL includes:<sup id="cite_ref-PCLman_11-1" class="reference"><a href="#cite_note-PCLman-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> </p> <ul><li>flow control: DO While/Until, CASE/SELECT, IF-THEN-ELSE, GOTO</li> <li>character string operations (length, substring, concatenation)</li> <li>access to system information (date/time, file attributes, device characteristics)</li></ul> <div class="mw-heading mw-heading2"><h2 id="TOPS-20_today">TOPS-20 today</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=TOPS-20&action=edit&section=9" title="Edit section: TOPS-20 today"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Paul_Allen" title="Paul Allen">Paul Allen</a> maintained several publicly accessible historic computer systems before his death, including an <a href="/wiki/XKL" title="XKL">XKL</a> TOAD-2 running TOPS-20. </p><p>See also <a href="/wiki/SDF_Public_Access_Unix_System" title="SDF Public Access Unix System">SDF Public Access Unix System</a>. </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=TOPS-20&action=edit&section=10" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Time-sharing_system_evolution" title="Time-sharing system evolution">Time-sharing system evolution</a></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=TOPS-20&action=edit&section=11" 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-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></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 id="CITEREFRichard_Stallman1986" class="citation web cs1">Richard Stallman (30 October 1986). <a rel="nofollow" class="external text" href="https://www.gnu.org/philosophy/stallman-kth.html">"RMS lecture at KTH (Sweden)"</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=RMS+lecture+at+KTH+%28Sweden%29&rft.date=1986-10-30&rft.au=Richard+Stallman&rft_id=https%3A%2F%2Fwww.gnu.org%2Fphilosophy%2Fstallman-kth.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATOPS-20" class="Z3988"></span></span> </li> <li id="cite_note-CMDref-2"><span class="mw-cite-backlink">^ <a href="#cite_ref-CMDref_2-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-CMDref_2-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-CMDref_2-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-CMDref_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://livingcomputers.org/UI/UserDocs/TOPS-20-v7-1/2_TOPS-20_Commands_Reference_Manual.pdf">"TOPS-20 Command manual"</a> <span class="cs1-format">(PDF)</span>. Digital Equipement Corporation. September 1985.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=TOPS-20+Command+manual&rft.pub=Digital+Equipement+Corporation&rft.date=1985-09&rft_id=https%3A%2F%2Flivingcomputers.org%2FUI%2FUserDocs%2FTOPS-20-v7-1%2F2_TOPS-20_Commands_Reference_Manual.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATOPS-20" class="Z3988"></span></span> </li> <li id="cite_note-TENXref-3"><span class="mw-cite-backlink">^ <a href="#cite_ref-TENXref_3-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-TENXref_3-1"><sup><i><b>b</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="http://tenex.opost.com/hbook.html">"Origins and Development of TOPS-20"</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Origins+and+Development+of+TOPS-20&rft_id=http%3A%2F%2Ftenex.opost.com%2Fhbook.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATOPS-20" class="Z3988"></span></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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://dspace.mit.edu/bitstream/handle/1721.1/6165/AIM-161A.pdf">"ITS 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=ITS+reference+manual&rft_id=https%3A%2F%2Fdspace.mit.edu%2Fbitstream%2Fhandle%2F1721.1%2F6165%2FAIM-161A.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATOPS-20" class="Z3988"></span></span> </li> <li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</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.catb.org/jargon/html/T/TWENEX.html">"TWENEX"</a>. <i>The Jargon File</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=The+Jargon+File&rft.atitle=TWENEX&rft_id=http%3A%2F%2Fwww.catb.org%2Fjargon%2Fhtml%2FT%2FTWENEX.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATOPS-20" class="Z3988"></span></span> </li> <li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</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.abbreviations.com/term/223192">"What does UUO mean in Software?"</a>. <i>abbreviations.com</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=abbreviations.com&rft.atitle=What+does+UUO+mean+in+Software%3F&rft_id=http%3A%2F%2Fwww.abbreviations.com%2Fterm%2F223192&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATOPS-20" class="Z3988"></span></span> </li> <li id="cite_note-JSYS104-7"><span class="mw-cite-backlink">^ <a href="#cite_ref-JSYS104_7-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-JSYS104_7-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text">The 10/50 was the top-of-the-line KA machine at that time. <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDan_Murphy1989" class="citation web cs1">Dan Murphy (1989). <a rel="nofollow" class="external text" href="http://tenex.opost.com/hbook.html">"Origins and Development of TOPS-20"</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Origins+and+Development+of+TOPS-20&rft.date=1989&rft.au=Dan+Murphy&rft_id=http%3A%2F%2Ftenex.opost.com%2Fhbook.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATOPS-20" class="Z3988"></span> The family continued with another KA, the 10/55, and then came KI, KL & KS.</span> </li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text">The JSYS was the counterpart for the 20 of what was done by TOPS-10 on a "10" and thus the emulator for a DEC PDP-10 Model 50 was what PA1050 was emulating. The 10's system calls were known as UUO's</span> </li> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</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.columbia.edu/kermit/ftp/dec20/assembler-guide.txt">"DECSYSTEM-20 Assembly Language Guide"</a>. <i>The Kermit Project</i>. 3 July 1980.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=The+Kermit+Project&rft.atitle=DECSYSTEM-20+Assembly+Language+Guide&rft.date=1980-07-03&rft_id=http%3A%2F%2Fwww.columbia.edu%2Fkermit%2Fftp%2Fdec20%2Fassembler-guide.txt&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATOPS-20" class="Z3988"></span></span> </li> <li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</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://www.allacronyms.com/JSYS/Jump_to_System">"JSYS means Jump to System"</a>. <i>allacronyms.com</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=allacronyms.com&rft.atitle=JSYS+means+Jump+to+System&rft_id=https%3A%2F%2Fwww.allacronyms.com%2FJSYS%2FJump_to_System&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATOPS-20" class="Z3988"></span></span> </li> <li id="cite_note-PCLman-11"><span class="mw-cite-backlink">^ <a href="#cite_ref-PCLman_11-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-PCLman_11-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation book cs1"><i>TOPS-20 Programmable Command Language / User's Guide and Reference Manual</i>. Carnegie Mellon University Computation Center. 1981.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=TOPS-20+Programmable+Command+Language+%2F+User%27s+Guide+and+Reference+Manual&rft.pub=Carnegie+Mellon+University+Computation+Center&rft.date=1981&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATOPS-20" class="Z3988"></span></span> </li> <li id="cite_note-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-12">^</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://fileformats.archiveteam.org/wiki/Programmable_Command_Language">"Programmable Command Language"</a>. <i>fileformats.archiveteam.org</i>. March 11, 2016.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=fileformats.archiveteam.org&rft.atitle=Programmable+Command+Language&rft.date=2016-03-11&rft_id=http%3A%2F%2Ffileformats.archiveteam.org%2Fwiki%2FProgrammable_Command_Language&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATOPS-20" class="Z3988"></span></span> </li> <li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFR._J._Cohn1988" class="citation web cs1">R. J. Cohn (1988). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20030926230320/http://reports-archive.adm.cs.cmu.edu/anon/scan/CMU-CS-88-139.pdf">"Programmable Command Languages for Window System"</a> <span class="cs1-format">(PDF)</span>. Archived from <a rel="nofollow" class="external text" href="http://reports-archive.adm.cs.cmu.edu/anon/scan/CMU-CS-88-139.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 2003-09-26.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Programmable+Command+Languages+for+Window+System&rft.date=1988&rft.au=R.+J.+Cohn&rft_id=http%3A%2F%2Freports-archive.adm.cs.cmu.edu%2Fanon%2Fscan%2FCMU-CS-88-139.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATOPS-20" class="Z3988"></span></span> </li> <li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFRay_Scott1983" class="citation web cs1">Ray Scott (12 January 1983). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20081007044359/http://www.math.utah.edu/~bowman/pcl.txt">"TOPS-20 Programmable Command Language"</a>. Archived from <a rel="nofollow" class="external text" href="http://www.math.utah.edu/~bowman/pcl.txt">the original</a> on 2008-10-07.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=TOPS-20+Programmable+Command+Language&rft.date=1983-01-12&rft.au=Ray+Scott&rft_id=http%3A%2F%2Fwww.math.utah.edu%2F~bowman%2Fpcl.txt&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATOPS-20" class="Z3988"></span></span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="Further_reading">Further reading</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=TOPS-20&action=edit&section=12" title="Edit section: Further reading"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><i><a rel="nofollow" class="external text" href="http://tenex.opost.com/fjcc72/">Storage Organization and Management in TENEX</a></i>. Daniel L. Murphy. AFIPS Proceedings, 1972 FJCC.</li> <li><i>Implementation of TENEX on the KI10</i>. Daniel L. Murphy. TENEX Panel Session, NCC 1974.</li> <li>"<a rel="nofollow" class="external text" href="http://tilt.twenex.org">TOPS-20 User's Guide</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20140107050623/http://tilt.twenex.org/">Archived</a> 2014-01-07 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>." 1988.</li> <li>"<a rel="nofollow" class="external text" href="http://www.columbia.edu/kermit/ftp/dec20/assembler-guide.txt">DECSYSTEM-20 Assembly Language Guide</a>." Frank da Cruz and Chris Ryland, 1980.</li> <li>"<a rel="nofollow" class="external text" href="http://gunkies.org/wiki/Running_TOPS-20_V4.1_under_SIMH">Running TOPS-20 V4.1 under the SIMH Emulator</a>."</li></ul> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=TOPS-20&action=edit&section=13" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a rel="nofollow" class="external text" href="http://www.vt100.net/timeline/1976.html">DIGITAL Computing Timeline</a></li> <li><a rel="nofollow" class="external text" href="http://tenex.opost.com/hbook.html">Origins and Development of TOPS-20</a> is an excellent longer history.</li> <li><a rel="nofollow" class="external text" href="http://panda.trailing-edge.com">Panda TOPS-20 distribution</a>.</li> <li><a rel="nofollow" class="external text" href="http://www.twenex.org">SDF Public Access TWENEX</a>.</li> <li><a rel="nofollow" class="external text" href="http://simh.trailing-edge.com">SIMH Simulator</a> capable of simulating the PDP-10 and running TOPS-20.</li> <li><a rel="nofollow" class="external text" href="http://www.36bit.org/dec/manual/">Manuals for DEC 36-bit computers</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20140302093233/http://www.36bit.org/dec/manual/">Archived</a> 2014-03-02 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>.</li> <li><a rel="nofollow" class="external text" href="http://pdp-10.trailing-edge.com">PDP-10 Software Archive</a>.</li> <li><a rel="nofollow" class="external text" href="http://www.inwap.com/pdp10/">36-bits Forever</a>.</li> <li><a rel="nofollow" class="external text" href="https://livingcomputers.org/Computer-Collection/Online-Systems/Request-A-Login.aspx">Request a login</a> to <a href="/wiki/Living_Computers:_Museum_%2B_Labs" title="Living Computers: Museum + Labs">Living Computers: Museum + Labs</a> TOAD-2 running TOPS-20.</li></ul> <div class="navbox-styles"><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 .hlist .mw-empty-li{display:none}.mw-parser-output .hlist dt::after{content:": "}.mw-parser-output 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class="navbox-title" colspan="3"><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:Digital_Equipment_Corporation" title="Template:Digital Equipment Corporation"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Digital_Equipment_Corporation" title="Template talk:Digital Equipment Corporation"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Digital_Equipment_Corporation" title="Special:EditPage/Template:Digital Equipment Corporation"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Digital_Equipment_Corporation" style="font-size:114%;margin:0 4em"><a href="/wiki/Digital_Equipment_Corporation" title="Digital Equipment Corporation">Digital Equipment Corporation</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Key people</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Ken_Olsen" title="Ken Olsen">Ken Olsen</a> (founder and CEO, 1957–1992)</li> <li><a href="/wiki/Harlan_Anderson" title="Harlan Anderson">Harlan Anderson</a> (co-founder)</li> <li><a href="/wiki/Gordon_Bell" title="Gordon Bell">Gordon Bell</a> (VP of engineering)</li> <li><a href="/wiki/Robert_Palmer_(computer_businessman)" title="Robert Palmer (computer businessman)">Robert Palmer</a> (CEO, 1992–1998)</li></ul> </div></td><td class="noviewer navbox-image" rowspan="9" style="width:1px;padding:0 0 0 2px"><div><span class="mw-default-size" typeof="mw:File/Frameless"><a href="/wiki/File:Digital_Equipment_Corporation_1993_logo.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/90/Digital_Equipment_Corporation_1993_logo.svg/110px-Digital_Equipment_Corporation_1993_logo.svg.png" decoding="async" width="110" height="33" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/90/Digital_Equipment_Corporation_1993_logo.svg/165px-Digital_Equipment_Corporation_1993_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/90/Digital_Equipment_Corporation_1993_logo.svg/220px-Digital_Equipment_Corporation_1993_logo.svg.png 2x" data-file-width="3124" data-file-height="938" /></a></span></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Instruction_set_architecture" title="Instruction set architecture">Instruction set<br />architectures</a>,<br /><a href="/wiki/Processor_(computing)" title="Processor (computing)">processors</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/PDP-11_architecture" title="PDP-11 architecture">PDP-11</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li>LSI-11</li> <li>F-11</li> <li><a href="/wiki/DEC_T-11" title="DEC T-11">T-11</a></li> <li><a href="/wiki/DEC_J-11" title="DEC J-11">J-11</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/VAX" title="VAX">VAX</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/DEC_V-11" title="DEC V-11">V-11</a></li> <li><a href="/wiki/MicroVAX_78032" title="MicroVAX 78032">MicroVAX 78032</a></li> <li><a href="/wiki/CVAX" title="CVAX">CVAX</a> <ul><li><a href="/wiki/CVAX#SOC" title="CVAX">SOC</a></li></ul></li> <li><a href="/wiki/Rigel_(microprocessor)" title="Rigel (microprocessor)">Rigel</a> <ul><li><a href="/wiki/Rigel_(microprocessor)#Mariah" title="Rigel (microprocessor)">Mariah</a></li></ul></li> <li><a href="/wiki/NVAX" title="NVAX">NVAX</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/DEC_Alpha" title="DEC Alpha">Alpha</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Alpha_21064" title="Alpha 21064">Alpha 21064</a> <ul><li><a href="/wiki/Alpha_21064#Alpha_21066" title="Alpha 21064">21066</a></li> <li><a href="/wiki/Alpha_21064#Alpha_21068" title="Alpha 21064">21068</a></li></ul></li> <li><a href="/wiki/Alpha_21164" title="Alpha 21164">Alpha 21164</a> (<a href="/wiki/Alpha_21164#Alpha_21164PC_(PCA56)" title="Alpha 21164">21164PC</a>)</li> <li><a href="/wiki/Alpha_21264" title="Alpha 21264">Alpha 21264</a></li> <li><a href="/wiki/Alpha_21364" title="Alpha 21364">Alpha 21364</a></li> <li><a href="/wiki/Alpha_21464" title="Alpha 21464">Alpha 21464</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Other</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/DEC_PRISM" title="DEC PRISM">MicroPRISM</a></li> <li><a href="/wiki/StrongARM" title="StrongARM">StrongARM</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Computer_terminal" title="Computer terminal">Computer<br />terminals</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/VT05" title="VT05">VT05</a> (1970)</li> <li><a href="/wiki/DEC_GT40" title="DEC GT40">GT40</a> (1972)</li> <li><a href="/wiki/VT52" title="VT52">VT50/VT52</a> (1975)</li> <li><a href="/wiki/VT55" class="mw-redirect" title="VT55">VT55</a></li> <li><a href="/wiki/VT62" class="mw-redirect" title="VT62">VT62</a></li> <li><a href="/wiki/VT100" title="VT100">VT100</a> (1978)</li> <li><a href="/wiki/VT101" class="mw-redirect" title="VT101">VT101</a></li> <li><a href="/wiki/VT102" class="mw-redirect" title="VT102">VT102</a></li> <li><a href="/wiki/VT103" class="mw-redirect" title="VT103">VT103</a></li> <li><a href="/wiki/VT105" class="mw-redirect" title="VT105">VT105</a></li> <li><a href="/wiki/VT131" class="mw-redirect" title="VT131">VT131</a></li> <li><a href="/wiki/VT180" title="VT180">VT180</a></li> <li><a href="/wiki/VT220" title="VT220">VT220</a> (1983)</li> <li><a href="/wiki/VT240" class="mw-redirect" title="VT240">VT240</a></li> <li><a href="/wiki/VT241" class="mw-redirect" title="VT241">VT241</a></li> <li><a href="/wiki/VT320" title="VT320">VT320</a> (1987)</li> <li><a href="/wiki/VT330" class="mw-redirect" title="VT330">VT330</a></li> <li><a href="/wiki/VT340" class="mw-redirect" title="VT340">VT340</a></li> <li><a href="/wiki/VT420" title="VT420">VT420</a> (1990)</li> <li><a href="/wiki/VT1000" title="VT1000">VT1000</a> (1990)</li> <li><a href="/wiki/VT510" class="mw-redirect" title="VT510">VT510</a> (1993)</li> <li><a href="/wiki/VT520" title="VT520">VT520</a> (1994)</li> <li><a href="/wiki/VT525" class="mw-redirect" title="VT525">VT525</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Operating_system" title="Operating system">Operating<br />systems</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/PDP-7#Software" title="PDP-7">DECsys</a></li> <li><a href="/wiki/4K_Disk_Monitor_System" class="mw-redirect" title="4K Disk Monitor System">4K DMS</a></li> <li><a href="/wiki/Commercial_Operating_System" title="Commercial Operating System">COS</a></li> <li><a href="/wiki/TOPS-10" title="TOPS-10">TOPS-10</a></li> <li><a href="/wiki/RSX-15" class="mw-redirect" title="RSX-15">RSX-15</a></li> <li><a href="/wiki/TSS/8" title="TSS/8">TSS/8</a></li> <li><a href="/wiki/OS/8" title="OS/8">OS/8</a></li> <li><a href="/wiki/DEC_BATCH-11/DOS-11" title="DEC BATCH-11/DOS-11">DOS-11</a></li> <li><a href="/wiki/RT-11" title="RT-11">RT-11</a></li> <li><a href="/wiki/RSTS/E" title="RSTS/E">RSTS/E</a></li> <li><a href="/wiki/RSX-11" title="RSX-11">RSX-11</a> <ul><li><a href="/wiki/Interactive_Application_System" title="Interactive Application System">IAS</a></li></ul></li> <li><a href="/wiki/MUMPS#1970s" title="MUMPS">DSM-11</a></li> <li><a class="mw-selflink selflink">TOPS-20</a></li> <li><a href="/wiki/OpenVMS" title="OpenVMS">VAX/VMS</a></li> <li><a href="/wiki/VAXELN" title="VAXELN">VAXELN</a></li> <li><a href="/wiki/Ultrix" title="Ultrix">Ultrix</a></li> <li><a href="/wiki/DEC_MICA" title="DEC MICA">MICA</a></li> <li><a href="/wiki/Digital_UNIX" class="mw-redirect" title="Digital UNIX">Digital UNIX</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Programming_language" title="Programming language">Programming<br />languages</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/BASIC-8" title="BASIC-8">BASIC-8</a></li> <li><a href="/wiki/DIBOL" title="DIBOL">DIBOL</a></li> <li><a href="/wiki/FOCAL_(programming_language)" title="FOCAL (programming language)">FOCAL</a></li> <li><a href="/wiki/MACRO-10" title="MACRO-10">MACRO-10</a></li> <li><a href="/wiki/MACRO-11" title="MACRO-11">MACRO-11</a></li> <li><a href="/wiki/MUMPS" title="MUMPS">MUMPS</a></li> <li><a href="/wiki/VAX_MACRO" title="VAX MACRO">VAX MACRO</a></li> <li><a href="/wiki/DIGITAL_Command_Language" title="DIGITAL Command Language">DIGITAL Command Language</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Character_encoding" title="Character encoding">Character sets</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Multinational_Character_Set" title="Multinational Character Set">Code page 1100</a> (Multinational)</li> <li><a href="/wiki/Code_page_1287" title="Code page 1287">Code page 1287</a> (Greek)</li> <li><a href="/wiki/Code_page_1288" title="Code page 1288">Code page 1288</a> (Turkish)</li> <li><a href="/wiki/DEC_Hebrew" title="DEC Hebrew">Hebrew</a></li> <li><a href="/wiki/National_Replacement_Character_Set" title="National Replacement Character Set">National Replacement</a></li> <li><a href="/wiki/DEC_RADIX_50" title="DEC RADIX 50">RADIX 50</a></li> <li><a href="/wiki/DEC_Special_Graphics" title="DEC Special Graphics">Special Graphics</a></li> <li><a href="/wiki/DEC_Technical_Character_Set" title="DEC Technical Character Set">Technical</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Bus_(computing)" title="Bus (computing)">Bus standards</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Digital_Storage_Systems_Interconnect" title="Digital Storage Systems Interconnect">Digital Storage Systems Interconnect</a></li> <li><a href="/wiki/Massbus" title="Massbus">Massbus</a></li> <li><a href="/wiki/Q-Bus" title="Q-Bus">Q-Bus</a></li> <li><a href="/wiki/Standard_Disk_Interconnect" title="Standard Disk Interconnect">Standard Disk Interconnect</a></li> <li><a href="/wiki/Synchronous_Backplane_Interconnect" title="Synchronous Backplane Interconnect">Synchronous Backplane Interconnect</a></li> <li><a href="/wiki/TURBOchannel" title="TURBOchannel">TURBOchannel</a></li> <li><a href="/wiki/Unibus" title="Unibus">Unibus</a></li> <li><a href="/wiki/VAXBI_bus" title="VAXBI bus">VAXBI bus</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Other <a href="/wiki/Computer_hardware" title="Computer hardware">hardware</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/DECtalk" title="DECtalk">DECtalk</a></li> <li><a href="/wiki/DECtape" title="DECtape">DECtape</a></li> <li><a href="/wiki/DECwriter" title="DECwriter">DECwriter</a></li> <li><a href="/wiki/Digital_Linear_Tape" title="Digital Linear Tape">Digital Linear Tape</a></li> <li><a href="/wiki/Dynamically_Redefined_Character_Set" title="Dynamically Redefined Character Set">Dynamically Redefined Character Set</a></li> <li><a href="/wiki/Firefly_(cache_coherence_protocol)" title="Firefly (cache coherence protocol)">Firefly</a></li> <li><a href="/wiki/Flip-Chip_module" title="Flip-Chip module">Flip-Chip module</a></li> <li><a href="/wiki/Gold_key_(DEC)" title="Gold key (DEC)">Gold key</a></li> <li><a href="/wiki/LK201" title="LK201">LK201</a></li> <li><a href="/wiki/LK421" title="LK421">LK421</a></li> <li><a href="/wiki/Mass_Storage_Control_Protocol" title="Mass Storage Control Protocol">Mass Storage Control Protocol</a></li> <li><a href="/wiki/PALcode" title="PALcode">PALcode</a></li> <li><a href="/wiki/RA90" title="RA90">RA90</a></li> <li><a href="/wiki/RK05" title="RK05">RK05</a></li> <li><a href="/wiki/RL02" title="RL02">RL02</a></li> <li><a href="/wiki/Star_coupler" title="Star coupler">Star coupler</a></li> <li><a href="/wiki/System_Module" title="System Module">System Module</a></li> <li><a href="/wiki/TU81" title="TU81">TU81</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Related topics</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/AdvFS" title="AdvFS">AdvFS</a></li> <li><a href="/wiki/AltaVista" title="AltaVista">AltaVista</a></li> <li><a href="/wiki/Compaq" title="Compaq">Compaq</a></li> <li><i><a href="/wiki/CPU_Wars" title="CPU Wars">CPU Wars</a></i></li> <li><a href="/wiki/DECnet" title="DECnet">DECnet</a></li> <li><a href="/wiki/DECUS" title="DECUS">DECUS</a> <ul><li><a href="/wiki/HP-Interex" title="HP-Interex">HP-Interex</a></li></ul></li> <li><a href="/wiki/Digital_Federal_Credit_Union" title="Digital Federal Credit Union">Digital Federal Credit Union</a></li> <li><a href="/wiki/Dynamic_debugging_technique" title="Dynamic debugging technique">Dynamic debugging technique</a></li> <li><a href="/wiki/FX!32" title="FX!32">FX!32</a></li> <li><a href="/wiki/Local_Area_Transport" title="Local Area Transport">Local Area Transport</a></li> <li><a href="/wiki/Maintenance_Operations_Protocol" title="Maintenance Operations Protocol">Maintenance Operations Protocol</a></li> <li><a href="/wiki/On-line_Debugging_Tool" title="On-line Debugging Tool">On-line Debugging Tool</a></li> <li><a href="/wiki/PALcode" title="PALcode">PALcode</a></li> <li><a href="/wiki/Record_Management_Services" title="Record Management Services">Record Management Services</a></li> <li><a href="/wiki/ReGIS" title="ReGIS">ReGIS</a></li> <li>Sequence and Batch Language</li> <li><a href="/wiki/Sixel" title="Sixel">Sixel</a></li> <li><a href="/wiki/System_Reference_Manual" class="mw-redirect" title="System Reference Manual">System Reference Manual</a></li> <li><a href="/wiki/DEC_Systems_Research_Center" title="DEC Systems Research Center">Systems Research Center</a></li> <li><a href="/wiki/TD/SMP" title="TD/SMP">TD/SMP</a></li> <li><i><a href="/wiki/The_Ultimate_Entrepreneur" title="The Ultimate Entrepreneur">The Ultimate Entrepreneur</a></i></li> <li><a href="/wiki/VT640" title="VT640">VT640</a></li> <li><a href="/wiki/WPS-8" title="WPS-8">WPS-8</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="3"><div> <ul><li><span class="noviewer" typeof="mw:File"><span title="Template"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Symbol_template_class_pink.svg/16px-Symbol_template_class_pink.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Symbol_template_class_pink.svg/23px-Symbol_template_class_pink.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/83/Symbol_template_class_pink.svg/31px-Symbol_template_class_pink.svg.png 2x" data-file-width="180" data-file-height="185" /></span></span> <a href="/wiki/Template:DEC_hardware" title="Template:DEC hardware">Computers template</a></li> <li><span class="noviewer" typeof="mw:File"><span title="Category"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/16px-Symbol_category_class.svg.png" 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