flag day

3 definitions found

flag day - WordNet (r) 2.1 (2005) :

  Flag Day
      n 1: commemorating the adoption of the United States flag in
           1777 [syn: Flag Day, June 14]

flag day - Free On-line Dictionary of Computing (26 May 2007) :

  flag day
  
     <jargon> A software change that is neither forward- nor
     backward-compatible, and which is costly to make and costly to
     reverse.  E.g. "Can we install that without causing a flag day
     for all users?"
  
     This term has nothing to do with the use of the word flag to
     mean a variable that has two values.  It came into use when a
     massive change was made to the Multics time-sharing system
     to convert from the old ASCII code to the new one; this was
     scheduled for Flag Day (a US holiday), June 14, 1966.
  
     See also backward combatability, lock-in.
  
     [Jargon File]
  
     (1998-01-15)
  

flag day - Jargon File (4.4.4, 14 Aug 2003) :

  flag day
   n.
  
     A software change that is neither forward- nor backward-compatible,
     and which is costly to make and costly to reverse. "Can we install
     that without causing a flag day for all users?" This term has nothing
     to do with the use of the word flag to mean a variable that has two
     values. It came into use when a change was made to the definition of
     the ASCII character set during the development of Multics. The
     change was scheduled for Flag Day (a U.S. holiday), June 14, 1966.
  
     The change altered the Multics definition of ASCII from the
     short-lived 1965 version of the ASCII code to the 1967 version (in
     draft at the time); this moved code points for braces, vertical bar,
     and circumflex. See also backward combatability. The Great Renaming
      was a flag day.
  
     [Most of the changes were made to files stored on CTSS, the system
     used to support Multics development before it became self-hosting.]
  
     [As it happens, the first installation of a commercially-produced
     computer, a Univac I, took place on Flag Day of 1951 --ESR]