Related:

• 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?...
• backward combatability: /bak'w*rd k*m-bat'*-bil'*-tee/ [from `backward compatibility'] n.
  A property of hardware or software revisions in which previous protocols, formats, layouts, etc....
• flag: n. A variable or quantity that can take on one of two value
  a bit, particularly one that is used to indicate one of two outcomes or is used to control which of two things is to be done....
• flag n. [very common] A variable or quantity that can take on one of two value
  a bit, particularly one that is used to indicate one of two outcomes or is used to control which of two things is to be done....
• mode bit: n. A {flag}, usually in hardware, that selects between two (usually quite different) modes of operation.
  The connotations are different from {flag} bit in that mode bits are mainly written during a boot or set-up phase, are seldom explicitly read, and seldom change over the lifetime of an ordinary program....
• backward combatability /bak'w*rd k*m-bat'*-bil'*-tee/ n.
  [CMU, Tektronix: from `backward compatibility'] A property of hardware or software revisions in which previous protocols, formats, layouts, etc....
• Great Renaming: n. The {flag day} in 1985 on which all of the non-local groups on the {USENET} had their names changed from the net.
  format to the current multiple-hierarchies scheme....
• hidden flag: [scientific computation] n. An extra option added to a routine without changing the calling sequence.
  For example, instead of adding an explicit input variable to instruct a routine to give extra diagnostic output, the programmer might just add a test for some otherwise meaningless feature of the existing inputs, such as a negative mass....
• ecurity through obscurity (alt. `security by obscurity') A term applied by hackers to most OS vendors' favorite way of coping with security holes -- namely
  ignoring them, documenting neither any known holes nor the underlying security algorithms, trusting that nobody will find out about them and that people who do find out about them won't exploit them....