4.3BSD-Tahoe/usr/src/old/vpr/READ_ME

This directory contains software written at UCB to drive Versatec
and Benson-Varian electrostatic plotters.
The versatec uses 36 inch wide roll paper; the varian uses 11 x 11 inch
fanfold paper.
Some of the software is proprietary and has not been included,
but can be obtained from Versatec.

We have the versatec running as a plotter, a printer (four pages
across using the hardware characters), and a typesetter (also
running four pages across).
The varian does all these things too, but only one page across.

The varian is known as /dev/va0.  The versatec is /dev/vp0.
Much of the software is shared, and can be used for either device.
Only the daemons are separate (vad and vpd).  But even they are produced
from the same source file (vpd.c).