|Noun||1.||Flag Day - commemorating the adoption of the U.S. flag in 1777|
Synonyms: June 14
|(jargon)||flag day - 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.