out-of-band

   [from telecommunications and network theory]

   1.  In  software, describes values of a function which are not in its
   `natural'  range  of  return values, but are rather signals that some
   kind of exception has occurred. Many C functions, for example, return
   a   nonnegative   integral   value,  but  indicate  failure  with  an
   out-of-band return value of -1. Compare {hidden flag}, {green bytes},
   {fence}.

   2.  Also  sometimes  used to describe what communications people call
   shift  characters,  such  as the ESC that leads control sequences for
   many terminals, or the level shift indicators in the old 5-bit Baudot
   codes.

   3. In personal communication, using methods other than email, such as
   telephones or {snail-mail}.

[glossary]
[Reference(s) to this entry by made by: {EOF}{fence}{green bytes}]