Dynamic Link Library

   A collection of subroutines which are linked with a program at
the time it is loaded into memory rather than permanently placed in the
executable.  This has the advantage of allowing a single copy of the
subroutine library to reside on disk or in memory even when it is used
by many programs.  It also permits all programs using the DLL to be
updated without recompiling simply by installing a new version of the
library.