MenuCat reads a disk in DF1. While MenuCat is reading a disk,
the display changes to inform the user that the volume in question is being
processed. When MenuCat finishes with a volume, a ``finished'' message is
presented to the user. The user then replaces the disk in DF1 with the next
disk to be cataloged. Output to the MenuCat window is to cue the user to
proceed with disk swaps. Output to ``stdout'' is as described in section 2.1.