mgdiff is a graphical front-end to the UNIX diff command based upon X11R[456] and the Motif widget set. It allows the user to select two files for comparison, runs the diff command, parses the output, and presents the results graphically. This presentation can also be used to generate a user-specified merge of the two files into a third file. This program's appearance is based upon a program called gdiff, which runs only on Silicon Graphics workstations and for which source code is not provided.