The IF MODified (IFMOD) program is a poor mans Module
Management System (DEC/MMS).  It supplies one of the key
features of DEC/MMS, which is the ability to determine if a
source file has been modified since the last time it was
compilied.  IFMOD compares the modification dates of
specified files, and depending on whether the results are
true or false, it executes a user specified DCL command (the
syntax of the IFMOD command is similar to the DCL IF
command).  The basic idea is:  If file A is used to generate
file B, then IFMOD can be used to determine if file A has
been changed (since the last time file B was created) and
re-generate file B if necessary.  Complete HELP instructions
(including examples) are supplied with the program which
describe its use and syntax.