The "prerex" editor allows interactive editing of the chart environments
of LaTeX source files that use prerex.sty. It supports add, remove,
cut-and-paste, and edit operations on course boxes and arrows, and
vertical or horizontal shifts of the whole diagram or selected sets of
course boxes. When a course box is moved, the arrows into and out of it
automatically follow.

The effects of editing operations may be observed in any PDF viewer.
The "vprerex" (visual prerex) application (not included here) is a GUI
and viewer for the prerex editor. It may be used just as a minimalistic
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 back to the prerex editor command-line
using the clipboard.

