2014-04-26 10:52:28 -04:00
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flag day
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2014-04-26 11:54:15 -04:00
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n. A software change that is neither forward- nor backward-compatible, and
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which is costly to make and costly to reverse. Can we install that without
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causing a flag day for all users? This term has nothing to do with the use
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of the word flag to mean a variable that has two values. It came into use
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when a change was made to the definition of the ASCII character set during
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the development of Multics. The change was scheduled for Flag Day (a U.S.
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holiday), June 14, 1966. The change altered the Multics definition of ASCII
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from the short-lived 1965 version of the ASCII code to the 1967 version (in
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draft at the time); this moved code points for braces, vertical bar, and
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circumflex. See also backward combatability. The Great Renaming was a flag
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day. [Most of the changes were made to files stored on CTSS , the system
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used to support Multics development before it became self-hosting.
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