21 lines
2.9 KiB
HTML
21 lines
2.9 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>flag day</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="../F.html" title="F"/><link rel="previous" href="flag.html" title="flag"/><link rel="next" href="flaky.html" title="flaky"/></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">flag day</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="flag.html">Prev</a> </td><th width="60%" align="center">F</th><td width="20%" align="right"> <a accesskey="n" href="flaky.html">Next</a></td></tr></table><hr/></div><dt><a id="flag-day"/><dt xmlns="" id="flag-day"><b>flag day</b>: <span xmlns="http://www.w3.org/1999/xhtml" class="grammar">n.</span></dt></dt><dd><p> A software change that is neither forward- nor
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backward-compatible, and which is costly to make and costly
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to reverse. “<span class="quote">Can we install that without causing a
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flag day for all users?</span>” This term has nothing to do
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with the use of the word <a href="flag.html"><i class="glossterm">flag</i></a> to mean
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a variable that has two values. It came into use when a
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change was made to the definition of the ASCII character set
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during the development of <a href="../M/Multics.html"><i class="glossterm">Multics</i></a>.
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The change was scheduled for Flag Day (a U.S. holiday),
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June 14, 1966.</p><p>The change altered the Multics definition of ASCII from the
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short-lived 1965 version of the ASCII code to the 1967 version (in draft at
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the time); this moved code points for braces, vertical bar, and
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circumflex. See also <a href="../B/backward-combatability.html"><i class="glossterm">backward combatability</i></a>. The
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<a href="../G/Great-Renaming.html"><i class="glossterm">Great Renaming</i></a> was a flag day. </p></dd><dd><p>[Most of the changes were made to files stored on
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<a href="../C/CTSS.html"><i class="glossterm">CTSS</i></a>, the system used to support
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Multics development before it became self-hosting.]
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</p><p>[As it happens, the first installation of a
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commercially-produced computer, a Univac I, took place on
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Flag Day of 1951 —ESR]</p></dd><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="flag.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="../F.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="flaky.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">flag </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> flaky</td></tr></table></div></body></html>
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