Prerex is an interactive program for editing prerequisite-chart
descriptions in the prerex format. The user does not normally have to be
familiar with details of the format. The editor supports add, remove,
cut-and-paste, and edit operations on diagram elements, and horizontal
or vertical shifts of a list of specified elements, all the elements in
a rectangular region, or the entire diagram. The edited diagram may be
saved, re-processed, and viewed in a PDF viewer, without exiting the
editor.

The effects of editing operations may be observed in any PDF viewer. The
"vprerex" (visual prerex) application (not included here) is a graphical
front-end and viewer for the prerex editor. It may be used just as a
minimalist viewer of arbitrary PDF files but supports editing of charts
generated using prerex.sty by allowing coordinates of course boxes,
arrows, and background points to be conveyed over to the prerex editor
command-line using the clipboard.

