25 lines
3.9 KiB
HTML
25 lines
3.9 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>bit</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="../B.html" title="B"/><link rel="previous" href="binary-four.html" title="binary four"/><link rel="next" href="bit-bang.html" title="bit bang"/></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">bit</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="binary-four.html">Prev</a> </td><th width="60%" align="center">B</th><td width="20%" align="right"> <a accesskey="n" href="bit-bang.html">Next</a></td></tr></table><hr/></div><dt><a id="bit"/><dt xmlns="" id="bit"><b>bit</b>: <span xmlns="http://www.w3.org/1999/xhtml" class="grammar">n.</span></dt></dt><dd><p> [from the mainstream meaning and “<span class="quote">Binary digIT</span>”]</p></dd><dd><p> 1. [techspeak] The unit of information; the amount of information
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obtained from knowing the answer to a yes-or-no question for which the two
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outcomes are equally probable. </p></dd><dd><p> 2. [techspeak] A computational quantity that can take on one of two
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values, such as true and false or 0 and 1. </p></dd><dd><p> 3. A mental flag: a reminder that something should be done
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eventually. “<span class="quote">I have a bit set for you.</span>” (I haven't seen you
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for a while, and I'm supposed to tell or ask you something.) </p></dd><dd><p> 4. More generally, a (possibly incorrect) mental state of belief.
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“<span class="quote">I have a bit set that says that you were the last guy to hack on
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EMACS.</span>” (Meaning “<span class="quote">I think you were the last guy to hack on
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EMACS, and what I am about to say is predicated on this, so please stop me
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if this isn't true.</span>”) “<span class="quote">I just need one bit from you</span>” is
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a polite way of indicating that you intend only a short interruption for a
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question that can presumably be answered yes or no.</p><p>A bit is said to be <span class="firstterm">set</span> if its
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value is true or 1, and <span class="firstterm">reset</span> or
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<span class="firstterm">clear</span> if its value is false or 0.
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One speaks of setting and clearing bits. To <a href="../T/toggle.html"><i class="glossterm">toggle</i></a>
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or <span class="firstterm">invert</span> a bit is to change it,
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either from 0 to 1 or from 1 to 0. See also <a href="../F/flag.html"><i class="glossterm">flag</i></a>,
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<a href="../T/trit.html"><i class="glossterm">trit</i></a>, <a href="../M/mode-bit.html"><i class="glossterm">mode bit</i></a>.</p></dd><dd><p>The term <span class="firstterm">bit</span> first appeared in
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print in the computer-science sense in a 1948 paper by information theorist
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Claude Shannon, and was there credited to the early computer scientist John
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Tukey (who also seems to have coined the term <span class="firstterm">software</span>). Tukey records that <span class="firstterm">bit</span> evolved over a lunch table as a handier
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alternative to <span class="firstterm">bigit</span> or <span class="firstterm">binit</span>, at a conference in the winter of
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1943-44.</p></dd><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="binary-four.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="../B.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bit-bang.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">binary four </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> bit bang</td></tr></table></div></body></html>
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