These are some comments on the interface provided by GNU libplot to
Tektronix emulators.

The Tektronix device driver included in libplot produces output for several
types of Tektronix-compatible display.  This includes the Tektronix
emulators built into `xterm' (the X Window System terminal emulator) and
the MS-DOS version of `kermit'.  They are recognized by the environment
variable TERM equalling "xterm" (or "xterms" or "kterm"), and "kermit" (or
"ansi.sys, "ansi.sysk", "ansisys", or "ansisysk"), respectively.

If there is any chance that you will be displaying output on a genuine
Tektronix storage tube, you should compile with the -DGENUINE_TEKTRONIX
option.  The only change that will make is adding a 1-second delay after
each `erase screen' command, if neither of the two above sorts of emulator
is being used.  Tektronix storage tubes take that long to clear.

Some historical comments on the Tektronix 4010/4014 follow. 

A Tektronix 4010 had what was effectively a 1024x780 display, as did the
first Tektronix 4014 models.  Effective coordinate space was
[0..1023]x[0..779].  Extended resolution, available for Tektronix 4014's
equipped with the Enhanced Graphics Module [EGM], yielded
[0..4095]x[0..3119] as coordinate space.  Actually the range of the two
position registers was always [0..4095], even before the EGM was
introduced.  (On displays without EGM, the low two bits in each coordinate
were dropped.)  So the upgrade path to the 4014-with-EGM was smooth.

In pre-EGM days a Tekpoint increment (display measurement unit) equalled
four increments of the x or y position register.  `Home cursor position'
was (0,767) in terms of Tekpoints, since the character matrix was 7x9.
After the introduction of the EGM, a Tekpoint increment equalled one
increment of the x or y position register, not four.  Home position became
(0,3071).

There were approximately 70 Tekpoints/inch in pre-EGM days, 280/inch with
EGM.  In other words, the resolution was better than that of high-end
workstation displays today.  Who says raster graphics is an improvement
over vector graphics?
