Compares two files, two generations of elements, or a file and
    a generation of an element. If the entities are different, CMS
    creates a file that contains the lines that differ between them.
    If they are the same, CMS issues a message to that effect and does
    not create a differences file (unless the /FULL qualifier is in
    effect).

       Format:

          DIFFERENCES  file1 [file2]