38 lines
4.5 KiB
HTML
38 lines
4.5 KiB
HTML
<?xml version="1.0" encoding="ISO-8859-1" standalone="no"?>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><title>DDT</title><link rel="stylesheet" href="../../jargon.css" type="text/css"/><meta name="generator" content="DocBook XSL Stylesheets V1.61.0"/><link rel="home" href="../index.html" title="The Jargon File"/><link rel="up" href="../D.html" title="D"/><link rel="previous" href="dd.html" title="dd"/><link rel="next" href="de-rezz.html" title="de-rezz"/></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">DDT</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="dd.html">Prev</a> </td><th width="60%" align="center">D</th><td width="20%" align="right"> <a accesskey="n" href="de-rezz.html">Next</a></td></tr></table><hr/></div><dt><a id="DDT"/><dt xmlns="" id="DDT"><b>DDT</b>: <span xmlns="http://www.w3.org/1999/xhtml" class="pronunciation">/D·D·T/</span>, <span xmlns="http://www.w3.org/1999/xhtml" class="grammar">n.</span></dt></dt><dd><p> [from the insecticide para-dichloro-diphenyl-trichloroethene]
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</p></dd><dd><p> 1. Generic term for a program that assists in debugging other
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programs by showing individual machine instructions in a readable symbolic
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form and letting the user change them. In this sense the term DDT is now
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archaic, having been widely displaced by <span class="firstterm">debugger</span> or names of individual programs like
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<b class="command">adb</b>, <b class="command">sdb</b>,
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<b class="command">dbx</b>, or <b class="command">gdb</b>. </p></dd><dd><p> 2. [ITS] Under MIT's fabled <a href="../I/ITS.html"><i class="glossterm">ITS</i></a> operating
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system, DDT (running under the alias HACTRN, a six-letterism for
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‘Hack Translator’) was also used as the
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<a href="../S/shell.html"><i class="glossterm">shell</i></a> or top level command language used to execute
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other programs. </p></dd><dd><p> 3. Any one of several specific DDTs (sense 1) supported on early
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<a href="DEC.html"><i class="glossterm">DEC</i></a> hardware and CP/M. The PDP-10 Reference
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Handbook (1969) contained a footnote on the first page of the documentation
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for DDT that illuminates the origin of the term:</p><div class="blockquote"><blockquote class="blockquote"><p>Historical footnote: DDT was developed at MIT for the PDP-1
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computer in 1961. At that time DDT stood for “<span class="quote">DEC Debugging
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Tape</span>”. Since then, the idea of an on-line debugging program has
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propagated throughout the computer industry. DDT programs are now
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available for all DEC computers. Since media other than tape are
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now frequently used, the more descriptive name “<span class="quote">Dynamic Debugging
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Technique</span>” has been adopted, retaining the DDT abbreviation. Confusion
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between DDT-10 and another well known pesticide,
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dichloro-diphenyl-trichloroethane
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C<sub>14</sub>H<sub>9</sub>Cl<sub>5</sub>
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should be minimal since each attacks a
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different, and apparently mutually exclusive, class of bugs.</p></blockquote></div><p>(The ‘tape’ referred to was, incidentally, not magnetic
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but paper.) Sadly, this quotation was removed from later editions of the
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handbook after the <a href="../S/suit.html"><i class="glossterm">suit</i></a>s took over and
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<a href="DEC.html"><i class="glossterm">DEC</i></a> became much more
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‘businesslike’.</p><p>The history above is known to many old-time hackers. But there's
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more: Peter Samson, compiler of the original <a href="../T/TMRC.html"><i class="glossterm">TMRC</i></a>
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lexicon, reports that he named <span class="firstterm">DDT</span>
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after a similar tool on the TX-0 computer, the direct ancestor of the PDP-1
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built at MIT's Lincoln Lab in 1957. The debugger on that ground-breaking
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machine (the first transistorized computer) rejoiced in the name FLIT
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(FLexowriter Interrogation Tape). Flit was for many years the trade-name
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of a popular insecticide.</p></dd><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="dd.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="../D.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="de-rezz.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">dd </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> de-rezz</td></tr></table></div></body></html>
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