<programming> (Or "procedure") A sequence of instructions
for performing a particular task. Most programming languages,
including most machine languages, allow the programmer to
define subroutines. This allows the subroutine code to be
called from multiple places, even from within itself (in which
case it is called recursive). The programming language
implementation takes care of returning control to (just after)
the calling location, usually with the support of call and
return instructions at machine language level.

Most languages also allow arguments to be passed to the
subroutine, and one, or occasionally more, return values to
be passed back.

A function is often very similar to a subroutine, the main
difference being that it is called chiefly for its return
value, rather than for any side effects.

(1996-10-01)