The Unix Time Sharing System

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Dennis Ritchie和Ken Thompson两位大师关于Unix的论文,经典之作,研究OS/Unix/Linux的人可以考虑看下
The Unix Time Sharing System.7z
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内容介绍
<html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta charset="utf-8"> <meta name="generator" content="pdf2htmlEX"> <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"> <link rel="stylesheet" href="https://static.pudn.com/base/css/base.min.css"> <link rel="stylesheet" href="https://static.pudn.com/base/css/fancy.min.css"> <link rel="stylesheet" href="https://static.pudn.com/prod/directory_preview_static/6291cb49bf399b7f353162f8/raw.css"> <script src="https://static.pudn.com/base/js/compatibility.min.js"></script> <script src="https://static.pudn.com/base/js/pdf2htmlEX.min.js"></script> <script> try{ pdf2htmlEX.defaultViewer = new pdf2htmlEX.Viewer({}); }catch(e){} </script> <title></title> </head> <body> <div id="sidebar" style="display: none"> <div id="outline"> </div> </div> <div id="pf1" class="pf w0 h0" data-page-no="1"><div class="pc pc1 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/6291cb49bf399b7f353162f8/bg1.jpg"><div class="t m0 x1 h2 y1 ff1 fs0 fc0 sc0 ls0 ws0"><span class="fc0 sc0">The </span><span class="_ _0"></span><span class="ls1"><span class="fc0 sc0">UNIX </span><span class="_ _1"></span><span class="ls2"><span class="fc0 sc0">Time- </span></span></span></div><div class="t m0 x2 h2 y2 ff1 fs0 fc0 sc0 ls3 ws0"><span class="fc0 sc0">Sharing </span><span class="_ _2"></span><span class="ls4"><span class="fc0 sc0">System </span></span></div><div class="t m1 x1 h3 y3 ff2 fs1 fc0 sc0 ls5 ws0"><span class="fc0 sc0">Dennis </span><span class="_ _3"></span><span class="ls6"><span class="fc0 sc0">M. </span><span class="_ _3"></span><span class="ls7"><span class="fc0 sc0">Ritchie </span><span class="_ _4"></span><span class="ls8"><span class="fc0 sc0">and </span><span class="_ _4"></span><span class="ls9"><span class="fc0 sc0">Ken </span><span class="_ _1"></span><span class="lsa"><span class="fc0 sc0">Thompson </span></span></span></span></span></span></div><div class="t m1 x1 h3 y4 ff2 fs1 fc0 sc0 lsb ws0"><span class="fc0 sc0">Bell </span><span class="_ _5"></span><span class="lsc"><span class="fc0 sc0">Laboratories </span></span></div><div class="t m2 x3 h4 y5 ff2 fs2 fc0 sc0 ls4 ws0"><span class="fc0 sc0">UNIX </span><span class="_ _5"></span><span class="ls2"><span class="fc0 sc0">is </span><span class="_ _4"></span></span><span class="fc0 sc0">a </span><span class="_"> </span><span class="lsd"><span class="fc0 sc0">general-purpose, </span><span class="_ _3"></span><span class="ls7"><span class="fc0 sc0">multi-user, </span><span class="_ _4"></span><span class="lse"><span class="fc0 sc0">interactive </span></span></span></span></div><div class="t m3 x1 h5 y6 ff1 fs2 fc0 sc0 ls5 ws0"><span class="fc0 sc0">operating </span><span class="_ _4"></span><span class="lsf"><span class="fc0 sc0">system </span><span class="_ _3"></span><span class="ls7"><span class="fc0 sc0">for </span></span></span></div><div class="t m2 x4 h4 y6 ff2 fs2 fc0 sc0 ls10 ws0"><span class="fc0 sc0">the </span><span class="_ _4"></span><span class="ls11"><span class="fc0 sc0">Digital </span><span class="_ _3"></span><span class="lsd"><span class="fc0 sc0">Equipment </span></span></span></div><div class="t m3 x5 h5 y6 ff1 fs2 fc0 sc0 ls12 ws0"><span class="fc0 sc0">Corporation </span></div><div class="t m2 x1 h4 y7 ff2 fs2 fc0 sc0 ls13 ws0"><span class="fc0 sc0">PDP-11/40 </span><span class="_ _3"></span><span class="ls7"><span class="fc0 sc0">and </span><span class="_ _3"></span><span class="ls14"><span class="fc0 sc0">11/45 </span><span class="_ _6"> </span><span class="ls15"><span class="fc0 sc0">computers. </span><span class="_ _4"></span><span class="ls16"><span class="fc0 sc0">It </span><span class="ls17"><span class="fc0 sc0">offers </span><span class="_ _5"></span><span class="ls4"><span class="fc0 sc0">a </span><span class="_ _6"> </span><span class="ls5"><span class="fc0 sc0">number </span><span class="ls12"><span class="fc0 sc0">of </span></span></span></span></span></span></span></span></span></div><div class="t m2 x1 h4 y8 ff2 fs2 fc0 sc0 ls18 ws0"><span class="fc0 sc0">features </span><span class="_ _5"></span><span class="ls17"><span class="fc0 sc0">seldom </span><span class="_ _4"></span><span class="ls19"><span class="fc0 sc0">found </span><span class="_ _4"></span><span class="ls1a"><span class="fc0 sc0">even </span><span class="ls2"><span class="fc0 sc0">in </span><span class="_ _4"></span><span class="ls16"><span class="fc0 sc0">larger </span><span class="_ _4"></span><span class="ls1b"><span class="fc0 sc0">operating </span><span class="_ _5"></span></span></span></span></span></span></span><span class="fc0 sc0">systems, </span></div><div class="t m2 x1 h4 y9 ff2 fs2 fc0 sc0 ls1c ws0"><span class="fc0 sc0">including: </span><span class="_ _7"> </span><span class="ls1d"><span class="fc0 sc0">(1) </span><span class="_ _8"> </span><span class="ls4"><span class="fc0 sc0">a </span><span class="_ _8"> </span><span class="ls1e"><span class="fc0 sc0">hierarchical </span><span class="_ _6"> </span><span class="lsb"><span class="fc0 sc0">file </span><span class="ls11"><span class="fc0 sc0">system </span></span></span></span></span></span></div><div class="t m3 x6 h5 y9 ff1 fs2 fc0 sc0 ls5 ws0"><span class="fc0 sc0">incorporating </span></div><div class="t m2 x1 h4 ya ff2 fs2 fc0 sc0 lsd ws0"><span class="fc0 sc0">demountable </span><span class="_ _4"></span><span class="ls10"><span class="fc0 sc0">volumes; </span><span class="_ _8"></span><span class="ls4"><span class="fc0 sc0">(2) </span><span class="_"> </span><span class="ls1f"><span class="fc0 sc0">compatible </span><span class="_ _3"></span><span class="ls20"><span class="fc0 sc0">file, </span><span class="_ _4"></span><span class="ls0"><span class="fc0 sc0">device, </span></span></span></span></span></span></div><div class="t m3 x7 h5 ya ff1 fs2 fc0 sc0 ls10 ws0"><span class="fc0 sc0">and </span></div><div class="t m3 x1 h5 yb ff1 fs2 fc0 sc0 lsd ws0"><span class="fc0 sc0">inter-process </span></div><div class="t m2 x8 h4 yb ff2 fs2 fc0 sc0 ls1b ws0"><span class="fc0 sc0">I/O; </span><span class="_ _8"></span><span class="ls1d"><span class="fc0 sc0">(3) </span><span class="_ _8"></span><span class="ls10"><span class="fc0 sc0">the </span><span class="_ _4"></span><span class="ls14"><span class="fc0 sc0">ability </span><span class="_ _4"></span></span><span class="fc0 sc0">to </span><span class="_ _5"></span><span class="ls21"><span class="fc0 sc0">initiate </span><span class="_ _3"></span><span class="ls1e"><span class="fc0 sc0">asynchronous </span></span></span></span></span></div><div class="t m2 x2 h4 yc ff2 fs2 fc0 sc0 ls1c ws0"><span class="fc0 sc0">processes; </span><span class="_ _8"></span><span class="ls1d"><span class="fc0 sc0">(4) </span><span class="_ _3"></span><span class="ls16"><span class="fc0 sc0">system </span><span class="_ _5"></span><span class="ls11"><span class="fc0 sc0">command </span><span class="_ _5"></span></span><span class="fc0 sc0">language </span><span class="_ _4"></span><span class="ls22"><span class="fc0 sc0">selectable </span><span class="ls10"><span class="fc0 sc0">on </span><span class="_ _4"></span><span class="ls4"><span class="fc0 sc0">a </span></span></span></span></span></span></div><div class="t m2 x2 h4 yd ff2 fs2 fc0 sc0 ls18 ws0"><span class="fc0 sc0">per-user </span><span class="_ _4"></span><span class="ls10"><span class="fc0 sc0">basis; </span><span class="_ _4"></span><span class="ls7"><span class="fc0 sc0">and </span><span class="_ _8"></span><span class="ls1d"><span class="fc0 sc0">(5) </span><span class="_ _8"></span><span class="ls21"><span class="fc0 sc0">over </span><span class="ls23"><span class="fc0 sc0">100 </span><span class="_ _4"></span><span class="ls1f"><span class="fc0 sc0">subsystems </span><span class="_ _5"></span><span class="ls24"><span class="fc0 sc0">including </span><span class="_ _8"> </span><span class="ls4"><span class="fc0 sc0">a </span></span></span></span></span></span></span></span></span></div><div class="t m3 x2 h5 ye ff1 fs2 fc0 sc0 ls25 ws0"><span class="fc0 sc0">dozen </span></div><div class="t m2 x9 h4 ye ff2 fs2 fc0 sc0 ls18 ws0"><span class="fc0 sc0">languages. </span><span class="_ _3"></span><span class="ls21"><span class="fc0 sc0">This </span><span class="_ _4"></span><span class="ls25"><span class="fc0 sc0">paper </span><span class="_ _5"></span><span class="ls1a"><span class="fc0 sc0">discusses </span><span class="_ _4"></span><span class="ls10"><span class="fc0 sc0">the </span><span class="_ _4"></span><span class="ls5"><span class="fc0 sc0">nature </span></span></span></span></span></span></div><div class="t m3 xa h5 ye ff1 fs2 fc0 sc0 ls26 ws0"><span class="fc0 sc0">and </span></div><div class="t m2 x1 h4 yf ff2 fs2 fc0 sc0 ls18 ws0"><span class="fc0 sc0">implementation </span><span class="_ _5"></span><span class="ls12"><span class="fc0 sc0">of </span><span class="ls10"><span class="fc0 sc0">the </span><span class="_ _8"> </span><span class="lsb"><span class="fc0 sc0">file </span><span class="ls16"><span class="fc0 sc0">system </span><span class="ls7"><span class="fc0 sc0">and </span><span class="_ _4"></span><span class="lse"><span class="fc0 sc0">of </span></span></span></span></span><span class="fc0 sc0">the </span><span class="_ _3"></span><span class="ls27"><span class="fc0 sc0">user </span></span></span></span></div><div class="t m3 x1 h5 y10 ff1 fs2 fc0 sc0 ls9 ws0"><span class="fc0 sc0">command </span></div><div class="t m2 xb h4 y10 ff2 fs2 fc0 sc0 ls22 ws0"><span class="fc0 sc0">interface. </span></div><div class="t m2 x3 h4 y11 ff2 fs2 fc0 sc0 ls16 ws0"><span class="fc0 sc0">Key </span></div><div class="t m3 xc h5 y11 ff1 fs2 fc0 sc0 ls12 ws0"><span class="fc0 sc0">Words </span><span class="_ _3"></span><span class="ls26"><span class="fc0 sc0">and </span></span></div><div class="t m2 xd h4 y11 ff2 fs2 fc0 sc0 ls16 ws0"><span class="fc0 sc0">Phrases: </span><span class="_ _9"></span><span class="ls13"><span class="fc0 sc0">time-sharing, </span></span></div><div class="t m3 xe h5 y11 ff1 fs2 fc0 sc0 ls14 ws0"><span class="fc0 sc0">operating </span></div><div class="t m2 x1 h4 y12 ff2 fs2 fc0 sc0 ls1f ws0"><span class="fc0 sc0">system, </span><span class="_ _8"> </span><span class="ls2"><span class="fc0 sc0">file </span><span class="_ _5"></span></span><span class="fc0 sc0">system, </span><span class="_ _4"></span><span class="ls11"><span class="fc0 sc0">command </span><span class="ls5"><span class="fc0 sc0">language, </span><span class="_ _3"></span><span class="ls1a"><span class="fc0 sc0">PDP-11 </span></span></span></span></div><div class="t m2 xf h4 y13 ff2 fs2 fc0 sc0 ls16 ws0"><span class="fc0 sc0">CR </span><span class="_ _9"></span><span class="ls28"><span class="fc0 sc0">Categories: </span><span class="_ _4"></span><span class="ls29"><span class="fc0 sc0">4.30, </span><span class="_ _9"> </span><span class="ls27"><span class="fc0 sc0">4.32 </span></span></span></span></div><div class="t m3 x10 h5 y14 ff1 fs2 fc0 sc0 ls29 ws0"><span class="fc0 sc0">1. </span><span class="_ _a"> </span><span class="ls7"><span class="fc0 sc0">Introduction </span></span></div><div class="t m2 x11 h4 y15 ff2 fs2 fc0 sc0 ls16 ws0"><span class="fc0 sc0">There </span><span class="_ _3"></span><span class="ls1b"><span class="fc0 sc0">have </span><span class="_ _3"></span><span class="lsd"><span class="fc0 sc0">been </span><span class="_ _3"></span><span class="ls12"><span class="fc0 sc0">three </span><span class="_ _3"></span><span class="fc0 sc0">versions </span><span class="_ _3"></span><span class="ls2a"><span class="fc0 sc0">of </span><span class="ls4"><span class="fc0 sc0">UNIX. </span><span class="_ _1"></span><span class="ls16"><span class="fc0 sc0">The </span><span class="_ _4"></span><span class="lse"><span class="fc0 sc0">earliest </span></span></span></span></span></span></span></span></div><div class="t m2 x10 h4 y16 ff2 fs2 fc0 sc0 ls1f ws0"><span class="fc0 sc0">version </span><span class="_"> </span><span class="ls10"><span class="fc0 sc0">(circa </span><span class="_ _a"> </span><span class="fc0 sc0">196%70) </span><span class="_ _a"> </span><span class="ls16"><span class="fc0 sc0">ran </span><span class="_"> </span><span class="ls12"><span class="fc0 sc0">on </span><span class="_ _6"> </span><span class="ls14"><span class="fc0 sc0">the </span><span class="_"> </span><span class="ls8"><span class="fc0 sc0">Digital </span><span class="_ _6"> </span><span class="ls2b"><span class="fc0 sc0">Equipment </span></span></span></span></span></span></span></div><div class="t m2 x10 h4 y17 ff2 fs2 fc0 sc0 ls2c ws0"><span class="fc0 sc0">Corporation </span><span class="_ _6"> </span><span class="ls4"><span class="fc0 sc0">PDP-7 </span><span class="_ _b"> </span><span class="ls9"><span class="fc0 sc0">and </span><span class="_ _7"> </span><span class="ls2"><span class="fc0 sc0">-9 </span><span class="_ _6"> </span><span class="ls2d"><span class="fc0 sc0">computers. </span><span class="_ _7"> </span><span class="ls16"><span class="fc0 sc0">The </span><span class="_ _6"> </span><span class="ls13"><span class="fc0 sc0">second </span><span class="_ _7"> </span><span class="ls21"><span class="fc0 sc0">ver- </span></span></span></span></span></span></span></span></div><div class="t m2 x10 h4 y18 ff2 fs2 fc0 sc0 ls21 ws0"><span class="fc0 sc0">sion </span><span class="_ _6"> </span><span class="ls8"><span class="fc0 sc0">ran </span><span class="_ _7"> </span><span class="lse"><span class="fc0 sc0">on </span><span class="_ _6"> </span><span class="ls7"><span class="fc0 sc0">the </span><span class="_ _7"> </span><span class="ls2e"><span class="fc0 sc0">unprotected </span><span class="_ _7"> </span><span class="ls10"><span class="fc0 sc0">PDP-11/20 </span><span class="_ _8"> </span><span class="ls2f"><span class="fc0 sc0">computer. </span><span class="_ _7"> </span><span class="ls5"><span class="fc0 sc0">This </span></span></span></span></span></span></span></span></div><div class="t m2 x10 h4 y19 ff2 fs2 fc0 sc0 ls30 ws0"><span class="fc0 sc0">paper </span><span class="_ _3"></span><span class="lsd"><span class="fc0 sc0">describes </span><span class="_"> </span><span class="ls5"><span class="fc0 sc0">only </span><span class="_ _3"></span><span class="ls7"><span class="fc0 sc0">the </span><span class="_ _8"> </span><span class="ls31"><span class="fc0 sc0">PDP-I </span><span class="_ _0"></span><span class="lsd"><span class="fc0 sc0">1/40 </span><span class="_ _6"> </span><span class="ls8"><span class="fc0 sc0">and </span><span class="_ _6"> </span><span class="ls9"><span class="fc0 sc0">/45 </span><span class="_"> </span><span class="ls32"><span class="fc0 sc0">[1] </span><span class="_ _c"> </span><span class="ls11"><span class="fc0 sc0">system </span></span></span></span></span></span></span></span></span></span></div><div class="t m2 x10 h4 y1a ff2 fs2 fc0 sc0 ls6 ws0"><span class="fc0 sc0">since </span><span class="_ _c"> </span><span class="fc0 sc0">it </span><span class="_"> </span><span class="ls2"><span class="fc0 sc0">is </span><span class="_ _b"> </span><span class="ls2f"><span class="fc0 sc0">more </span><span class="_"> </span><span class="ls33"><span class="fc0 sc0">modern </span><span class="_"> </span><span class="ls16"><span class="fc0 sc0">and </span><span class="_ _a"> </span><span class="ls2b"><span class="fc0 sc0">many </span><span class="_ _7"> </span><span class="ls30"><span class="fc0 sc0">of </span><span class="_ _6"> </span><span class="ls7"><span class="fc0 sc0">the </span><span class="_ _c"> </span><span class="fc0 sc0">differences </span></span></span></span></span></span></span></span></div><div class="t m2 x10 h4 y1b ff2 fs2 fc0 sc0 ls1f ws0"><span class="fc0 sc0">between </span><span class="_ _8"> </span><span class="ls6"><span class="fc0 sc0">it </span><span class="_ _8"> </span><span class="ls8"><span class="fc0 sc0">and </span><span class="_ _7"> </span><span class="ls14"><span class="fc0 sc0">older </span><span class="_ _8"> </span><span class="ls4"><span class="fc0 sc0">UNIX </span><span class="_ _1"></span><span class="ls8"><span class="fc0 sc0">systems </span><span class="_ _4"></span><span class="lsd"><span class="fc0 sc0">result </span><span class="_ _8"> </span><span class="ls2f"><span class="fc0 sc0">from </span><span class="_ _3"></span><span class="ls21"><span class="fc0 sc0">redesign </span></span></span></span></span></span></span></span></span></div><div class="t m2 x10 h4 y1c ff2 fs2 fc0 sc0 ls2a ws0"><span class="fc0 sc0">of </span><span class="ls12"><span class="fc0 sc0">features </span><span class="_ _8"> </span><span class="ls16"><span class="fc0 sc0">found </span><span class="_ _6"> </span></span><span class="fc0 sc0">to </span><span class="_ _8"> </span><span class="lse"><span class="fc0 sc0">be </span><span class="_ _3"></span><span class="ls34"><span class="fc0 sc0">deficient </span><span class="_ _6"> </span></span><span class="fc0 sc0">or </span><span class="_ _9"></span><span class="fc0 sc0">lacking. </span></span></span></div><div class="t m2 x11 h4 y1d ff2 fs2 fc0 sc0 ls19 ws0"><span class="fc0 sc0">Since </span><span class="_ _6"> </span><span class="ls4"><span class="fc0 sc0">PDP-11 </span><span class="_ _c"> </span><span class="ls35"><span class="fc0 sc0">UNIX </span><span class="_ _0"></span><span class="lsf"><span class="fc0 sc0">became </span><span class="_ _8"> </span><span class="ls2e"><span class="fc0 sc0">operational </span><span class="_ _d"> </span><span class="ls2"><span class="fc0 sc0">in </span><span class="_"> </span><span class="ls2a"><span class="fc0 sc0">February </span></span></span></span></span></span></span></div><div class="t m2 x12 h4 y1e ff2 fs2 fc0 sc0 ls4 ws0"><span class="fc0 sc0">1971, </span><span class="_ _c"> </span><span class="ls36"><span class="fc0 sc0">about </span><span class="_ _8"> </span><span class="ls6"><span class="fc0 sc0">40 </span><span class="_ _9"> </span><span class="ls5"><span class="fc0 sc0">installations </span><span class="_ _7"> </span><span class="fc0 sc0">have </span><span class="_ _9"> </span><span class="lsd"><span class="fc0 sc0">been </span><span class="_ _8"> </span><span class="ls8"><span class="fc0 sc0">put </span><span class="_ _6"> </span></span></span><span class="fc0 sc0">into </span><span class="_ _8"> </span><span class="ls21"><span class="fc0 sc0">service; </span></span></span></span></span></div><div class="t m2 x10 h4 y1f ff2 fs2 fc0 sc0 ls5 ws0"><span class="fc0 sc0">they </span><span class="_ _a"> </span><span class="ls7"><span class="fc0 sc0">are </span><span class="_ _a"> </span><span class="ls14"><span class="fc0 sc0">generally </span><span class="_"> </span><span class="ls1f"><span class="fc0 sc0">smaller </span><span class="_ _c"> </span><span class="ls16"><span class="fc0 sc0">than </span><span class="_ _e"> </span></span></span></span><span class="fc0 sc0">the </span><span class="_ _a"> </span><span class="ls11"><span class="fc0 sc0">system </span><span class="_"> </span></span></span><span class="fc0 sc0">described </span></div><div class="t m2 x10 h4 y20 ff2 fs2 fc0 sc0 ls10 ws0"><span class="fc0 sc0">here. </span><span class="_ _7"> </span><span class="ls37"><span class="fc0 sc0">Most </span><span class="_ _8"> </span><span class="ls30"><span class="fc0 sc0">of </span><span class="ls2f"><span class="fc0 sc0">them </span><span class="_ _3"></span><span class="ls14"><span class="fc0 sc0">are </span><span class="_ _9"></span><span class="ls8"><span class="fc0 sc0">engaged </span><span class="_ _9"> </span><span class="ls2"><span class="fc0 sc0">in </span><span class="_ _6"> </span><span class="ls28"><span class="fc0 sc0">applications </span><span class="_ _8"> </span><span class="lsd"><span class="fc0 sc0">such </span><span class="_ _8"> </span><span class="ls6"><span class="fc0 sc0">as </span></span></span></span></span></span></span></span></span></span></div><div class="t m2 x10 h4 y21 ff2 fs2 fc0 sc0 ls7 ws0"><span class="fc0 sc0">the </span><span class="_"> </span><span class="ls2f"><span class="fc0 sc0">preparation </span><span class="_"> </span><span class="ls16"><span class="fc0 sc0">and </span><span class="_ _b"> </span><span class="ls38"><span class="fc0 sc0">formatting </span><span class="_ _7"> </span><span class="ls30"><span class="fc0 sc0">of </span><span class="_ _9"></span><span class="lsf"><span class="fc0 sc0">patent </span><span class="_ _d"> </span></span></span></span><span class="fc0 sc0">applications </span></span></span></div><div class="t m2 x10 h4 y22 ff2 fs2 fc0 sc0 ls16 ws0"><span class="fc0 sc0">and </span><span class="_ _3"></span><span class="ls25"><span class="fc0 sc0">other </span><span class="_ _4"></span><span class="ls14"><span class="fc0 sc0">textual </span><span class="_ _3"></span><span class="ls1b"><span class="fc0 sc0">material, </span><span class="_ _3"></span><span class="ls10"><span class="fc0 sc0">the </span><span class="_ _4"></span><span class="ls1e"><span class="fc0 sc0">collection </span><span class="_ _3"></span><span class="ls8"><span class="fc0 sc0">and </span><span class="_ _9"></span><span class="ls18"><span class="fc0 sc0">processing </span></span></span></span></span></span></span></span></div><div class="t m2 x12 h4 y23 ff2 fs2 fc0 sc0 ls30 ws0"><span class="fc0 sc0">of </span><span class="_ _1"></span><span class="ls16"><span class="fc0 sc0">trouble </span><span class="_ _9"> </span><span class="fc0 sc0">data </span><span class="_ _6"> </span><span class="ls33"><span class="fc0 sc0">from </span><span class="_ _5"></span></span><span class="fc0 sc0">various </span><span class="_ _3"></span><span class="lsd"><span class="fc0 sc0">switching </span><span class="_ _9"></span><span class="ls11"><span class="fc0 sc0">machines </span><span class="_ _3"></span><span class="ls22"><span class="fc0 sc0">within </span></span></span></span></span></div><div class="t m2 x10 h4 y24 ff2 fs2 fc0 sc0 ls7 ws0"><span class="fc0 sc0">the </span><span class="_ _6"> </span><span class="lsb"><span class="fc0 sc0">Bell </span><span class="_ _6"> </span><span class="ls15"><span class="fc0 sc0">System, </span><span class="_ _8"> </span><span class="ls9"><span class="fc0 sc0">and </span><span class="_ _8"> </span><span class="ls28"><span class="fc0 sc0">recording </span><span class="_ _6"> </span><span class="ls16"><span class="fc0 sc0">and </span><span class="_ _8"> </span><span class="ls1b"><span class="fc0 sc0">checking </span><span class="_ _9"> </span></span></span><span class="fc0 sc0">telephone </span></span></span></span></span></div><div class="t m2 x12 h4 y25 ff2 fs2 fc0 sc0 ls10 ws0"><span class="fc0 sc0">service </span><span class="_ _e"> </span><span class="ls14"><span class="fc0 sc0">orders. </span><span class="_ _f"> </span><span class="ls16"><span class="fc0 sc0">Our </span><span class="_ _10"> </span><span class="ls8"><span class="fc0 sc0">own </span><span class="_ _11"> </span><span class="ls18"><span class="fc0 sc0">installation </span><span class="_ _f"> </span><span class="ls2"><span class="fc0 sc0">is </span><span class="_ _e"> </span><span class="ls21"><span class="fc0 sc0">used </span><span class="_ _10"> </span></span></span></span></span><span class="fc0 sc0">mainly </span></span></span></div><div class="t m2 x12 h4 y26 ff2 fs2 fc0 sc0 ls8 ws0"><span class="fc0 sc0">for </span><span class="_ _11"> </span><span class="ls1b"><span class="fc0 sc0">research </span><span class="_ _10"> </span><span class="ls29"><span class="fc0 sc0">in </span><span class="_ _12"> </span><span class="lsc"><span class="fc0 sc0">operating </span><span class="_ _f"> </span><span class="lse"><span class="fc0 sc0">systems, </span><span class="_ _f"> </span><span class="ls1e"><span class="fc0 sc0">languages, </span><span class="_ _f"> </span><span class="ls2f"><span class="fc0 sc0">com- </span></span></span></span></span></span></span></div><div class="t m2 x12 h4 y27 ff2 fs2 fc0 sc0 ls16 ws0"><span class="fc0 sc0">puter </span><span class="_ _7"> </span><span class="ls1b"><span class="fc0 sc0">networks, </span><span class="_"> </span></span><span class="fc0 sc0">and </span><span class="_"> </span><span class="ls25"><span class="fc0 sc0">other </span><span class="_ _7"> </span><span class="ls5"><span class="fc0 sc0">topics </span><span class="_ _d"> </span><span class="ls2"><span class="fc0 sc0">in </span><span class="_"> </span><span class="ls2a"><span class="fc0 sc0">computer </span><span class="_ _6"> </span><span class="ls27"><span class="fc0 sc0">science, </span></span></span></span></span></span></div><div class="t m2 x12 h4 y28 ff2 fs2 fc0 sc0 ls16 ws0"><span class="fc0 sc0">and </span><span class="_"> </span><span class="lsd"><span class="fc0 sc0">also </span><span class="_"> </span><span class="ls14"><span class="fc0 sc0">for </span><span class="_ _7"> </span><span class="ls39"><span class="fc0 sc0">document </span><span class="_"> </span><span class="ls9"><span class="fc0 sc0">preparation. </span></span></span></span></span></div><div class="t m2 x11 h4 y29 ff2 fs2 fc0 sc0 ls9 ws0"><span class="fc0 sc0">Perhaps </span><span class="_ _a"> </span><span class="ls7"><span class="fc0 sc0">the </span><span class="_ _c"> </span><span class="ls33"><span class="fc0 sc0">most </span><span class="_ _b"> </span><span class="ls3a"><span class="fc0 sc0">important </span><span class="_ _a"> </span><span class="lsc"><span class="fc0 sc0">achievement </span><span class="_"> </span><span class="ls30"><span class="fc0 sc0">of </span><span class="_ _6"> </span><span class="ls3b"><span class="fc0 sc0">UNIX </span></span></span></span></span></span></span></div><div class="t m2 x12 h4 y2a ff2 fs2 fc0 sc0 ls2 ws0"><span class="fc0 sc0">is </span><span class="_ _e"> </span><span class="lse"><span class="fc0 sc0">to </span><span class="_ _e"> </span><span class="ls30"><span class="fc0 sc0">demonstrate </span><span class="_ _e"> </span><span class="ls16"><span class="fc0 sc0">that </span><span class="_ _10"> </span><span class="ls4"><span class="fc0 sc0">a </span><span class="_ _f"> </span><span class="ls11"><span class="fc0 sc0">powerful </span><span class="_ _e"> </span><span class="lsc"><span class="fc0 sc0">operating </span><span class="_ _a"> </span></span><span class="fc0 sc0">system </span></span></span></span></span></span></div><div class="t m2 x12 h4 y2b ff2 fs2 fc0 sc0 ls14 ws0"><span class="fc0 sc0">for </span><span class="_ _11"> </span><span class="fc0 sc0">interactive </span><span class="_ _11"> </span><span class="ls7"><span class="fc0 sc0">use </span><span class="_ _10"> </span><span class="ls21"><span class="fc0 sc0">need </span><span class="_ _10"> </span><span class="ls16"><span class="fc0 sc0">not </span><span class="_ _10"> </span><span class="ls10"><span class="fc0 sc0">be </span><span class="_ _11"> </span></span></span></span></span><span class="fc0 sc0">expensive </span><span class="_ _e"> </span><span class="lsd"><span class="fc0 sc0">either </span><span class="_ _10"> </span><span class="ls2"><span class="fc0 sc0">in </span></span></span></div><div class="t m2 x10 h4 y2c ff2 fs2 fc0 sc0 ls2d ws0"><span class="fc0 sc0">equipment </span><span class="_ _4"></span><span class="lse"><span class="fc0 sc0">or </span><span class="_ _1"></span><span class="ls2"><span class="fc0 sc0">in </span><span class="_ _3"></span><span class="ls36"><span class="fc0 sc0">human </span><span class="_ _4"></span><span class="ls15"><span class="fc0 sc0">effort: </span><span class="ls3c"><span class="fc0 sc0">UNIX </span><span class="_ _2"></span><span class="ls14"><span class="fc0 sc0">can </span><span class="_ _4"></span><span class="fc0 sc0">run </span><span class="_ _4"></span><span class="ls10"><span class="fc0 sc0">on </span><span class="_ _4"></span><span class="ls37"><span class="fc0 sc0">hardware </span></span></span></span></span></span></span></span></span></div><div class="t m2 x10 h4 y2d ff2 fs2 fc0 sc0 ls1f ws0"><span class="fc0 sc0">costing </span><span class="_ _a"> </span><span class="ls10"><span class="fc0 sc0">as </span><span class="_ _c"> </span><span class="ls1a"><span class="fc0 sc0">little </span><span class="_ _e"> </span></span><span class="fc0 sc0">as </span><span class="_ _a"> </span><span class="ls3d"><span class="fc0 sc0">$40,000, </span><span class="_ _10"> </span><span class="ls16"><span class="fc0 sc0">and </span><span class="_ _e"> </span><span class="ls3e"><span class="fc0 sc0">less </span><span class="_ _b"> </span><span class="ls37"><span class="fc0 sc0">than </span><span class="_ _e"> </span><span class="ls8"><span class="fc0 sc0">two </span><span class="_ _a"> </span></span><span class="fc0 sc0">man- </span></span></span></span></span></span></div><div class="t m2 x10 h4 y2e ff2 fs2 fc0 sc0 ls12 ws0"><span class="fc0 sc0">years </span><span class="_ _a"> </span><span class="ls21"><span class="fc0 sc0">were </span><span class="_ _a"> </span><span class="ls14"><span class="fc0 sc0">spent </span><span class="_ _e"> </span><span class="lse"><span class="fc0 sc0">on </span><span class="_ _e"> </span><span class="ls7"><span class="fc0 sc0">the </span><span class="_ _e"> </span><span class="ls16"><span class="fc0 sc0">main </span><span class="_ _e"> </span><span class="ls13"><span class="fc0 sc0">system </span><span class="_ _11"> </span><span class="ls5"><span class="fc0 sc0">software. </span><span class="_ _e"> </span><span class="ls8"><span class="fc0 sc0">Yet </span></span></span></span></span></span></span></span></span></div><div class="t m2 x10 h4 y2f ff2 fs2 fc0 sc0 ls3c ws0"><span class="fc0 sc0">UNIX </span><span class="_ _0"></span><span class="ls11"><span class="fc0 sc0">contains </span><span class="_ _9"></span><span class="ls4"><span class="fc0 sc0">a </span><span class="_ _6"> </span><span class="ls3a"><span class="fc0 sc0">number </span><span class="_ _3"></span><span class="ls30"><span class="fc0 sc0">of </span><span class="ls12"><span class="fc0 sc0">features </span><span class="_ _4"></span></span></span></span></span><span class="fc0 sc0">seldom </span><span class="_ _4"></span><span class="ls7"><span class="fc0 sc0">offered </span><span class="_ _4"></span><span class="lsd"><span class="fc0 sc0">even </span></span></span></span></div><div class="t m2 x10 h4 y30 ff2 fs2 fc0 sc0 ls29 ws0"><span class="fc0 sc0">in </span><span class="_ _7"> </span><span class="ls37"><span class="fc0 sc0">much </span><span class="_ _9"> </span><span class="ls5"><span class="fc0 sc0">larger </span><span class="_ _9"> </span><span class="ls21"><span class="fc0 sc0">systems. </span><span class="_ _6"> </span><span class="ls16"><span class="fc0 sc0">It </span><span class="_ _3"></span><span class="ls3f"><span class="fc0 sc0">is </span><span class="_ _9"></span></span><span class="fc0 sc0">hoped, </span><span class="_ _6"> </span><span class="ls12"><span class="fc0 sc0">however, </span><span class="_ _8"> </span><span class="ls7"><span class="fc0 sc0">the </span><span class="_ _6"> </span><span class="ls10"><span class="fc0 sc0">users </span></span></span></span></span></span></span></span></div><div class="t m2 x12 h4 y31 ff2 fs2 fc0 sc0 ls16 ws0"><span class="fc0 sc0">of </span><span class="ls4"><span class="fc0 sc0">UNIX </span><span class="_ _0"></span><span class="ls2"><span class="fc0 sc0">will </span><span class="_ _4"></span><span class="ls1a"><span class="fc0 sc0">find </span><span class="_ _3"></span><span class="ls37"><span class="fc0 sc0">that </span><span class="_ _4"></span><span class="ls7"><span class="fc0 sc0">the </span><span class="_ _8"> </span></span><span class="fc0 sc0">most </span><span class="_ _4"></span><span class="ls33"><span class="fc0 sc0">important </span><span class="_ _4"></span><span class="ls13"><span class="fc0 sc0">characteristics </span></span></span></span></span></span></span></div><div class="t m2 x12 h4 y32 ff2 fs2 fc0 sc0 ls30 ws0"><span class="fc0 sc0">of </span><span class="_ _0"></span><span class="ls7"><span class="fc0 sc0">the </span><span class="_ _4"></span><span class="ls11"><span class="fc0 sc0">system </span><span class="_ _0"></span><span class="ls14"><span class="fc0 sc0">are </span><span class="_ _4"></span><span class="ls0"><span class="fc0 sc0">its </span><span class="ls1c"><span class="fc0 sc0">simplicity, </span><span class="_ _4"></span><span class="ls21"><span class="fc0 sc0">elegance, </span><span class="_ _5"></span><span class="ls16"><span class="fc0 sc0">and </span><span class="_ _4"></span><span class="ls10"><span class="fc0 sc0">ease </span><span class="_ _4"></span><span class="ls30"><span class="fc0 sc0">of </span><span class="_ _0"></span><span class="ls3e"><span class="fc0 sc0">use. </span></span></span></span></span></span></span></span></span></span></span></div><div class="t m2 x13 h4 y33 ff2 fs2 fc0 sc0 ls26 ws0"><span class="fc0 sc0">Besides </span><span class="_ _10"> </span><span class="ls7"><span class="fc0 sc0">the </span><span class="_ _f"> </span><span class="ls13"><span class="fc0 sc0">system </span><span class="_ _10"> </span><span class="ls16"><span class="fc0 sc0">proper, </span><span class="_ _f"> </span><span class="ls10"><span class="fc0 sc0">the </span><span class="_ _13"> </span><span class="ls36"><span class="fc0 sc0">major </span><span class="_ _f"> </span><span class="ls39"><span class="fc0 sc0">programs </span></span></span></span></span></span></span></div><div class="t m2 x12 h4 y34 ff2 fs2 fc0 sc0 ls13 ws0"><span class="fc0 sc0">available </span><span class="_ _9"> </span><span class="ls25"><span class="fc0 sc0">under </span><span class="_ _d"> </span><span class="ls4"><span class="fc0 sc0">UNIX </span><span class="_ _4"></span><span class="lsd"><span class="fc0 sc0">are: </span><span class="_"> </span><span class="ls1f"><span class="fc0 sc0">assembler, </span><span class="_"> </span><span class="ls21"><span class="fc0 sc0">text </span><span class="_ _9"></span><span class="ls11"><span class="fc0 sc0">editor </span><span class="_"> </span></span></span></span></span></span><span class="fc0 sc0">based </span></span></div><div class="t m2 x12 h4 y35 ff2 fs2 fc0 sc0 lse ws0"><span class="fc0 sc0">on </span><span class="_ _4"></span><span class="ls40"><span class="fc0 sc0">QED </span><span class="_ _6"> </span><span class="ls4"><span class="fc0 sc0">[2], </span><span class="_ _8"> </span><span class="ls15"><span class="fc0 sc0">linking </span><span class="_ _9"></span><span class="ls14"><span class="fc0 sc0">loader, </span><span class="_ _8"> </span><span class="ls16"><span class="fc0 sc0">symbolic </span><span class="_ _5"></span><span class="ls13"><span class="fc0 sc0">debugger, </span><span class="_ _3"></span><span class="lsf"><span class="fc0 sc0">compiler </span></span></span></span></span></span></span></span></div><div class="t m2 x12 h4 y36 ff2 fs2 fc0 sc0 ls7 ws0"><span class="fc0 sc0">for </span><span class="_ _e"> </span><span class="ls4"><span class="fc0 sc0">a </span><span class="_ _10"> </span><span class="ls11"><span class="fc0 sc0">language </span><span class="_ _11"> </span><span class="ls25"><span class="fc0 sc0">resembling </span><span class="_ _a"> </span><span class="ls3e"><span class="fc0 sc0">BCPL </span><span class="_ _6"> </span><span class="ls32"><span class="fc0 sc0">[3] </span><span class="_ _10"> </span><span class="ls21"><span class="fc0 sc0">with </span><span class="_ _e"> </span><span class="ls12"><span class="fc0 sc0">types </span><span class="_ _e"> </span><span class="ls16"><span class="fc0 sc0">and </span></span></span></span></span></span></span></span></span></div><div class="t m2 x12 h4 y37 ff2 fs2 fc0 sc0 ls25 ws0"><span class="fc0 sc0">structures </span><span class="_ _a"> </span><span class="ls10"><span class="fc0 sc0">(C), </span><span class="_ _a"> </span></span><span class="fc0 sc0">interpreter </span><span class="_ _a"> </span><span class="ls14"><span class="fc0 sc0">for </span><span class="_"> </span><span class="ls4"><span class="fc0 sc0">a </span><span class="_ _a"> </span><span class="ls15"><span class="fc0 sc0">dialect </span><span class="_"> </span><span class="ls30"><span class="fc0 sc0">of </span><span class="_ _8"> </span><span class="ls41"><span class="fc0 sc0">BASIC, </span><span class="_ _4"></span><span class="lsd"><span class="fc0 sc0">text </span></span></span></span></span></span></span></div><div class="t m2 x12 h4 y38 ff2 fs2 fc0 sc0 ls38 ws0"><span class="fc0 sc0">formatting </span><span class="_"> </span><span class="ls39"><span class="fc0 sc0">program, </span><span class="_ _a"> </span><span class="ls42"><span class="fc0 sc0">Fortran </span><span class="_ _a"> </span><span class="ls1b"><span class="fc0 sc0">compiler, </span><span class="_ _e"> </span><span class="lsf"><span class="fc0 sc0">Snobol </span><span class="_ _a"> </span><span class="lsd"><span class="fc0 sc0">inter- </span></span></span></span></span></span></div><div class="t m2 x10 h4 y39 ff2 fs2 fc0 sc0 ls14 ws0"><span class="fc0 sc0">preter, </span><span class="_ _f"> </span><span class="ls30"><span class="fc0 sc0">top-down </span><span class="_ _12"> </span><span class="ls37"><span class="fc0 sc0">compiler-compiler </span><span class="_ _11"> </span><span class="ls1c"><span class="fc0 sc0">(TMC) </span><span class="_"> </span><span class="ls4"><span class="fc0 sc0">[4], </span><span class="_ _12"> </span><span class="ls1b"><span class="fc0 sc0">bot- </span></span></span></span></span></span></div><div class="t m2 x10 h4 y3a ff2 fs2 fc0 sc0 ls3a ws0"><span class="fc0 sc0">tom-up </span><span class="_ _5"></span><span class="ls2e"><span class="fc0 sc0">compiler-compiler </span><span class="_ _0"></span><span class="ls4"><span class="fc0 sc0">(YACC), </span><span class="ls2f"><span class="fc0 sc0">form </span><span class="ls22"><span class="fc0 sc0">letter </span><span class="lsc"><span class="fc0 sc0">generator, </span></span></span></span></span></span></div><div class="t m2 x10 h4 y3b ff2 fs2 fc0 sc0 ls36 ws0"><span class="fc0 sc0">macro </span><span class="_ _5"></span><span class="ls1b"><span class="fc0 sc0">processor </span><span class="_ _4"></span><span class="ls10"><span class="fc0 sc0">(M6) </span><span class="_"> </span><span class="ls4"><span class="fc0 sc0">[5], </span><span class="_ _4"></span><span class="ls16"><span class="fc0 sc0">and </span><span class="_ _4"></span><span class="ls37"><span class="fc0 sc0">permuted </span><span class="_ _5"></span><span class="lse"><span class="fc0 sc0">index </span><span class="_ _4"></span><span class="lsa"><span class="fc0 sc0">program. </span></span></span></span></span></span></span></span></div><div class="t m2 x11 h4 y3c ff2 fs2 fc0 sc0 ls2e ws0"><span class="fc0 sc0">There </span><span class="_ _9"></span><span class="ls29"><span class="fc0 sc0">is </span><span class="_ _8"> </span><span class="ls21"><span class="fc0 sc0">also </span><span class="_ _6"> </span><span class="ls4"><span class="fc0 sc0">a </span><span class="_"> </span><span class="ls16"><span class="fc0 sc0">host </span><span class="_ _6"> </span><span class="ls2a"><span class="fc0 sc0">of </span><span class="_ _5"></span></span></span></span></span></span><span class="fc0 sc0">maintenance, </span><span class="_ _7"> </span><span class="ls17"><span class="fc0 sc0">utility, </span><span class="_ _7"> </span><span class="ls8"><span class="fc0 sc0">recrea- </span></span></span></div><div class="t m2 x10 h4 y3d ff2 fs2 fc0 sc0 ls14 ws0"><span class="fc0 sc0">tion, </span><span class="_ _8"> </span><span class="ls16"><span class="fc0 sc0">and </span><span class="_ _3"></span><span class="ls11"><span class="fc0 sc0">novelty </span><span class="_ _4"></span><span class="ls2f"><span class="fc0 sc0">programs. </span><span class="_ _4"></span><span class="ls7"><span class="fc0 sc0">All </span><span class="_ _9"></span><span class="ls30"><span class="fc0 sc0">of </span><span class="lse"><span class="fc0 sc0">these </span><span class="_ _4"></span><span class="ls2b"><span class="fc0 sc0">programs </span><span class="_ _5"></span><span class="ls5"><span class="fc0 sc0">were </span></span></span></span></span></span></span></span></span></div><div class="t m2 x10 h4 y3e ff2 fs2 fc0 sc0 ls8 ws0"><span class="fc0 sc0">written </span><span class="_ _a"> </span><span class="ls17"><span class="fc0 sc0">locally. </span><span class="_ _a"> </span><span class="ls30"><span class="fc0 sc0">It </span><span class="_ _7"> </span><span class="ls2"><span class="fc0 sc0">is </span><span class="_ _c"> </span></span><span class="fc0 sc0">worth </span><span class="_"> </span><span class="ls16"><span class="fc0 sc0">noting </span><span class="_"> </span><span class="ls2f"><span class="fc0 sc0">that </span><span class="_"> </span><span class="ls14"><span class="fc0 sc0">the </span><span class="_ _a"> </span></span></span><span class="fc0 sc0">system </span><span class="_ _6"> </span><span class="ls29"><span class="fc0 sc0">is </span></span></span></span></span></div><div class="t m2 x10 h4 y3f ff2 fs2 fc0 sc0 ls11 ws0"><span class="fc0 sc0">totally </span><span class="_ _3"></span><span class="ls13"><span class="fc0 sc0">self-supporting. </span><span class="_ _6"> </span><span class="ls10"><span class="fc0 sc0">All </span><span class="_ _9"></span><span class="ls35"><span class="fc0 sc0">UNIX </span><span class="_ _14"></span><span class="ls11"><span class="fc0 sc0">software </span><span class="_ _3"></span><span class="ls29"><span class="fc0 sc0">is </span><span class="_ _4"></span><span class="ls38"><span class="fc0 sc0">maintained </span></span></span></span></span></span></span></div><div class="t m2 x10 h4 y40 ff2 fs2 fc0 sc0 ls2e ws0"><span class="fc0 sc0">under </span><span class="_ _e"> </span><span class="ls19"><span class="fc0 sc0">UNIX; </span><span class="ls24"><span class="fc0 sc0">likewise, </span><span class="_ _e"> </span><span class="ls1a"><span class="fc0 sc0">UNIX </span><span class="ls36"><span class="fc0 sc0">documents </span><span class="_"> </span><span class="ls8"><span class="fc0 sc0">are </span><span class="_"> </span><span class="lsc"><span class="fc0 sc0">generated </span></span></span></span></span></span></span></div><div class="t m2 x10 h4 y41 ff2 fs2 fc0 sc0 ls16 ws0"><span class="fc0 sc0">and </span><span class="_ _7"> </span><span class="ls36"><span class="fc0 sc0">formatted </span><span class="_ _7"> </span><span class="ls30"><span class="fc0 sc0">by </span><span class="_ _8"> </span><span class="ls14"><span class="fc0 sc0">the </span><span class="_ _7"> </span><span class="ls35"><span class="fc0 sc0">UNIX </span><span class="_ _0"></span><span class="ls11"><span class="fc0 sc0">editor </span><span class="_ _d"> </span><span class="ls9"><span class="fc0 sc0">and </span><span class="_ _7"> </span><span class="ls5"><span class="fc0 sc0">text </span><span class="_ _6"> </span><span class="ls39"><span class="fc0 sc0">formatting </span></span></span></span></span></span></span></span></span></div><div class="t m2 x10 h4 y42 ff2 fs2 fc0 sc0 ls2a ws0"><span class="fc0 sc0">program. </span></div><div class="t m2 x14 h4 y43 ff2 fs2 fc0 sc0 ls4 ws0"><span class="fc0 sc0">Copyright </span><span class="fc0 sc0">&#169; </span><span class="_ _6"> </span><span class="ls43"><span class="fc0 sc0">1974, </span><span class="_ _0"></span><span class="ls4"><span class="fc0 sc0">Association </span><span class="_ _0"></span><span class="ls1d"><span class="fc0 sc0">for </span><span class="_ _0"></span><span class="ls4"><span class="fc0 sc0">Computing </span><span class="_ _5"></span><span class="fc0 sc0">Machinery, </span><span class="_ _1"></span><span class="fc0 sc0">Inc. </span></span></span></span></span></div><div class="t m2 x1 h4 y44 ff2 fs2 fc0 sc0 ls4 ws0"><span class="fc0 sc0">General </span><span class="_ _d"> </span><span class="fc0 sc0">permission </span><span class="_ _8"> </span><span class="ls3f"><span class="fc0 sc0">to </span><span class="_"> </span></span><span class="fc0 sc0">republish, </span><span class="_"> </span><span class="fc0 sc0">but </span><span class="_ _d"> </span><span class="fc0 sc0">not </span><span class="_ _d"> </span><span class="ls1d"><span class="fc0 sc0">for </span><span class="_ _7"> </span></span><span class="fc0 sc0">profit, </span><span class="_ _6"> </span><span class="fc0 sc0">all </span><span class="_"> </span><span class="ls3f"><span class="fc0 sc0">or </span><span class="_ _6"> </span><span class="ls35"><span class="fc0 sc0">part </span></span></span></div><div class="t m2 x1 h4 y45 ff2 fs2 fc0 sc0 ls10 ws0"><span class="fc0 sc0">of </span><span class="ls4"><span class="fc0 sc0">this </span><span class="_ _9"></span><span class="fc0 sc0">material </span><span class="_ _3"></span><span class="fc0 sc0">is </span><span class="_ _3"></span><span class="fc0 sc0">granted </span><span class="_ _6"> </span><span class="fc0 sc0">provided </span><span class="_ _4"></span><span class="ls35"><span class="fc0 sc0">that </span></span></span></div><div class="t m4 x15 h6 y45 ff3 fs3 fc0 sc0 ls30 ws0"><span class="fc0 sc0">ACM's </span></div><div class="t m2 xe h4 y45 ff2 fs2 fc0 sc0 ls4 ws0"><span class="fc0 sc0">copyright </span><span class="_ _3"></span><span class="fc0 sc0">notice </span></div><div class="t m2 x1 h4 y46 ff2 fs2 fc0 sc0 ls44 ws0"><span class="fc0 sc0">is </span><span class="_ _3"></span><span class="ls2"><span class="fc0 sc0">given </span><span class="_ _14"></span><span class="ls4"><span class="fc0 sc0">and </span><span class="_ _8"> </span><span class="fc0 sc0">that </span><span class="_"> </span><span class="fc0 sc0">reference </span><span class="ls44"><span class="fc0 sc0">is </span><span class="_ _3"></span></span><span class="fc0 sc0">made </span><span class="_ _3"></span><span class="ls3f"><span class="fc0 sc0">to </span><span class="_ _3"></span></span><span class="fc0 sc0">the </span><span class="_ _9"> </span><span class="fc0 sc0">publication, </span><span class="_ _9"></span><span class="ls2"><span class="fc0 sc0">to </span><span class="_ _4"></span></span><span class="fc0 sc0">its </span><span class="_ _9"> </span><span class="fc0 sc0">date </span></span></span></div><div class="t m2 x2 h4 y47 ff2 fs2 fc0 sc0 ls6 ws0"><span class="fc0 sc0">of </span><span class="_ _4"></span><span class="ls4"><span class="fc0 sc0">issue, </span><span class="_ _3"></span><span class="fc0 sc0">and </span><span class="_ _d"> </span><span class="ls2"><span class="fc0 sc0">to </span><span class="_"> </span></span><span class="fc0 sc0">the </span><span class="_ _8"> </span><span class="fc0 sc0">fact </span><span class="_"> </span><span class="ls35"><span class="fc0 sc0">that </span><span class="_ _7"> </span></span><span class="fc0 sc0">reprinting </span><span class="_ _d"> </span><span class="fc0 sc0">privileges </span><span class="ls3e"><span class="fc0 sc0">were </span></span><span class="fc0 sc0">granted </span></span></div><div class="t m2 x2 h4 y48 ff2 fs2 fc0 sc0 ls3f ws0"><span class="fc0 sc0">by </span><span class="ls4"><span class="fc0 sc0">permission </span><span class="ls29"><span class="fc0 sc0">of </span><span class="_ _0"></span><span class="ls4"><span class="fc0 sc0">the </span><span class="_ _4"></span><span class="fc0 sc0">Association </span><span class="fc0 sc0">for </span><span class="_ _4"></span><span class="fc0 sc0">Computing </span><span class="_ _3"></span><span class="fc0 sc0">Machinery. </span></span></span></span></div><div class="t m2 x3 h4 y49 ff2 fs2 fc0 sc0 ls4 ws0"><span class="fc0 sc0">This </span><span class="_ _8"> </span><span class="ls44"><span class="fc0 sc0">is </span><span class="_ _8"> </span></span><span class="fc0 sc0">a </span><span class="_"> </span><span class="fc0 sc0">revised </span><span class="_ _1"></span><span class="fc0 sc0">version </span><span class="_ _4"></span><span class="ls6"><span class="fc0 sc0">of </span><span class="_ _5"></span></span><span class="fc0 sc0">a </span><span class="_"> </span><span class="ls2"><span class="fc0 sc0">paper </span></span><span class="fc0 sc0">presented </span><span class="_ _9"></span><span class="ls2"><span class="fc0 sc0">at </span><span class="_ _8"> </span></span><span class="fc0 sc0">the </span><span class="_ _b"> </span><span class="fc0 sc0">Fourth </span></div><div class="t m2 x2 h4 y4a ff2 fs2 fc0 sc0 ls4 ws0"><span class="fc0 sc0">ACM </span><span class="_ _3"></span><span class="fc0 sc0">Symposium </span><span class="ls3f"><span class="fc0 sc0">on </span><span class="_ _15"></span></span><span class="fc0 sc0">Operating </span><span class="_ _3"></span><span class="fc0 sc0">Systems </span><span class="fc0 sc0">Principles, </span><span class="fc0 sc0">IBM </span><span class="_ _3"></span><span class="fc0 sc0">Thomas </span></div><div class="t m2 x1 h4 y4b ff2 fs2 fc0 sc0 ls4 ws0"><span class="fc0 sc0">J. </span><span class="_ _5"></span><span class="fc0 sc0">Watson </span><span class="fc0 sc0">Research </span><span class="fc0 sc0">Center, </span><span class="fc0 sc0">Yorktown </span><span class="fc0 sc0">Heights, </span><span class="fc0 sc0">New </span><span class="_ _0"></span><span class="fc0 sc0">York, </span><span class="fc0 sc0">October </span></div><div class="t m2 x2 h4 y4c ff2 fs2 fc0 sc0 ls4 ws0"><span class="fc0 sc0">15-17, </span><span class="_"> </span><span class="fc0 sc0">1973. </span><span class="_ _3"></span><span class="fc0 sc0">Authors' </span><span class="_ _e"> </span><span class="fc0 sc0">address: </span><span class="_ _d"> </span><span class="ls2"><span class="fc0 sc0">Bell </span></span><span class="fc0 sc0">Laboratories, </span><span class="_ _e"> </span><span class="fc0 sc0">Murray </span><span class="_ _c"> </span><span class="fc0 sc0">Hill, </span></div><div class="t m2 x1 h4 y4d ff2 fs2 fc0 sc0 ls29 ws0"><span class="fc0 sc0">NJ </span><span class="ls45"><span class="fc0 sc0">07974. </span></span></div><div class="t m3 x1 h5 y4e ff1 fs2 fc0 sc0 ls4 ws0"><span class="fc0 sc0">365 </span></div><div class="t m3 x10 h5 y4f ff1 fs2 fc0 sc0 ls6 ws0"><span class="fc0 sc0">2. </span><span class="_ _a"> </span><span class="ls16"><span class="fc0 sc0">Hardware </span><span class="_ _15"></span><span class="ls10"><span class="fc0 sc0">and </span><span class="_ _4"></span></span><span class="fc0 sc0">Software </span><span class="_ _4"></span><span class="ls12"><span class="fc0 sc0">Environment </span></span></span></div><div class="t m2 x11 h4 y50 ff2 fs2 fc0 sc0 ls9 ws0"><span class="fc0 sc0">The </span><span class="_"> </span><span class="ls27"><span class="fc0 sc0">PDP-11/45 </span><span class="_ _11"> </span><span class="ls12"><span class="fc0 sc0">on </span><span class="_ _a"> </span><span class="ls14"><span class="fc0 sc0">which </span><span class="_ _a"> </span></span></span></span><span class="fc0 sc0">our </span><span class="_ _a"> </span><span class="ls1a"><span class="fc0 sc0">UNIX </span><span class="_ _1"></span><span class="ls8"><span class="fc0 sc0">installation </span><span class="_ _11"> </span><span class="ls2"><span class="fc0 sc0">is </span></span></span></span></div><div class="t m2 x10 h4 y51 ff2 fs2 fc0 sc0 ls2f ws0"><span class="fc0 sc0">implemented </span><span class="ls2"><span class="fc0 sc0">is </span><span class="_ _15"></span><span class="ls4"><span class="fc0 sc0">a </span><span class="_"> </span><span class="ls46"><span class="fc0 sc0">16-bit </span><span class="_ _5"></span><span class="ls37"><span class="fc0 sc0">word </span><span class="_ _9"> </span><span class="ls22"><span class="fc0 sc0">(8-bit </span><span class="_ _15"></span><span class="ls14"><span class="fc0 sc0">byte) </span><span class="_ _15"></span><span class="ls2b"><span class="fc0 sc0">computer </span><span class="ls5"><span class="fc0 sc0">with </span></span></span></span></span></span></span></span></span></div><div class="t m2 x12 h4 y52 ff2 fs2 fc0 sc0 ls10 ws0"><span class="fc0 sc0">144K </span><span class="_ _9"> </span><span class="ls25"><span class="fc0 sc0">bytes </span><span class="_ _9"> </span><span class="ls30"><span class="fc0 sc0">of </span><span class="ls1b"><span class="fc0 sc0">core </span><span class="_ _8"> </span><span class="ls47"><span class="fc0 sc0">memory; </span><span class="_ _4"></span><span class="ls35"><span class="fc0 sc0">UNIX </span><span class="_ _0"></span><span class="ls12"><span class="fc0 sc0">occupies </span><span class="_ _3"></span><span class="ls9"><span class="fc0 sc0">42K </span><span class="_ _8"> </span><span class="ls5"><span class="fc0 sc0">bytes. </span></span></span></span></span></span></span></span></span></div><div class="t m2 x10 h4 y53 ff2 fs2 fc0 sc0 ls1b ws0"><span class="fc0 sc0">This </span><span class="_ _8"> </span><span class="ls14"><span class="fc0 sc0">system, </span><span class="_ _6"> </span></span><span class="fc0 sc0">however, </span><span class="_ _8"> </span><span class="lse"><span class="fc0 sc0">includes </span><span class="_ _7"> </span><span class="ls4"><span class="fc0 sc0">a </span><span class="_ _c"> </span><span class="ls5"><span class="fc0 sc0">very </span><span class="_ _4"></span><span class="ls14"><span class="fc0 sc0">large </span><span class="_ _8"> </span><span class="ls48"><span class="fc0 sc0">number </span><span class="_ _8"> </span><span class="ls2a"><span class="fc0 sc0">of </span></span></span></span></span></span></span></div><div class="t m2 x10 h4 y54 ff2 fs2 fc0 sc0 ls22 ws0"><span class="fc0 sc0">device </span><span class="_ _4"></span><span class="ls1f"><span class="fc0 sc0">drivers </span><span class="_ _3"></span><span class="ls16"><span class="fc0 sc0">and </span><span class="_ _3"></span><span class="ls5"><span class="fc0 sc0">enjoys </span><span class="_ _3"></span><span class="ls4"><span class="fc0 sc0">a </span><span class="_ _6"> </span></span></span><span class="fc0 sc0">generous </span><span class="_ _3"></span><span class="ls2d"><span class="fc0 sc0">allotment </span><span class="_ _3"></span><span class="ls30"><span class="fc0 sc0">of </span><span class="ls25"><span class="fc0 sc0">space </span></span></span></span></span></span></div><div class="t m2 x10 h4 y4d ff2 fs2 fc0 sc0 ls9 ws0"><span class="fc0 sc0">for </span><span class="_"> </span><span class="ls10"><span class="fc0 sc0">I/O </span><span class="_"> </span><span class="ls14"><span class="fc0 sc0">buffers </span><span class="_"> </span><span class="ls16"><span class="fc0 sc0">and </span><span class="_ _a"> </span><span class="fc0 sc0">system </span><span class="_ _d"> </span><span class="ls11"><span class="fc0 sc0">tables; </span><span class="_ _a"> </span><span class="ls4"><span class="fc0 sc0">a </span><span class="_ _e"> </span><span class="ls38"><span class="fc0 sc0">minimal </span><span class="_"> </span><span class="lsf"><span class="fc0 sc0">system </span></span></span></span></span></span></span></span></div><div class="t m2 x10 h4 y55 ff2 fs2 fc0 sc0 ls4 ws0"><span class="fc0 sc0">Communications </span><span class="_ _16"> </span><span class="fc0 sc0">July </span><span class="_ _4"></span><span class="ls45"><span class="fc0 sc0">1974 </span></span></div><div class="t m2 x10 h4 y56 ff2 fs2 fc0 sc0 ls10 ws0"><span class="fc0 sc0">of </span><span class="_ _17"> </span><span class="ls4"><span class="fc0 sc0">Volume </span><span class="ls49"><span class="fc0 sc0">17 </span></span></span></div><div class="t m2 x10 h4 y57 ff2 fs2 fc0 sc0 ls4 ws0"><span class="fc0 sc0">the </span><span class="_ _4"></span><span class="fc0 sc0">ACM </span><span class="_ _18"> </span><span class="ls4a"><span class="fc0 sc0">Number </span><span class="_ _1"></span><span class="ls4"><span class="fc0 sc0">7 </span></span></span></div></div><div class="pi" data-data='{"ctm":[1.568627,0.000000,0.000000,1.568627,0.000000,0.000000]}'></div></div> </body> </html>
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