Editing Graphics development with vplot (section)

==Introduction==
The pen software package, developed by students in the Geophysics department
at Stanford University over many years, allows graphical data produced by
computer programs to be displayed on a wide variety of output devices,
including terminals and hard copy devices. Both vector and raster output
are supported. The filters allow the user to control the size, aspect ratio,
and position on the page independent of the program which produces the data.
Pen programs read files written in the vplot graphics metalanguage and
write commands appropriate to the various output devices.
The pen programs are all filters, and can be run in pipelines without
loss of function. Only rudimentary provisions for interaction are provided.

Terminals now supported include color Tektronix and
emulators (4105), monochrome Tektronix and emulators (4010)
(GraphOn, Selanar, Retrographics), Envision, DEC Regis (Gigi, VT125, VT220),
Imagen, PostScript (e. g., Apple LaserWriter), Printronix printer,
suntools, X, NEWS, and Rastertek.