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
{electronic mail}, such as telephone or {snail-mail}.
[{Jargon File}]
(1994-11-29)