Short info on Tektronix 4014

The Tektronix 4014 was one of the first graphics terminals
available commercially. It was introduced in 1974 (it was
a year I was born :-) ). It has introduced the revolutionary
technology called 'storage tube'. The terminal itself has
no graphics memory - the image was stored by the CRT tube
itself.

The trick was, that after drawing the image by the electron
beam, phosphors were kept glowing by another scanning beam.
This second beam was to weak to cause dark phosphors glow,
but not allowed the parts hitted by the drawing beam to go
out. Thus the static image was displayed forever without
any effort from the host computer. The drawback was, that
it was not possible to erase a part of the display - it had
to be erased completely, and the whole image needed to be
redrawn by the computer. The drawing was created by the 
moving electron beam, not by addressing 'pixels', so the
straight lines were really straight. The beam position is
specified in rectangular coordinate system with resolution
1024x768 (but resolution is a bit inadequate term - only
line endpoint were fixed to this 'raster' - the segments
between them were drawn by smooth linear interpolation).
The hardware of Tektronix 4014 allowed also to draw lines
with different dash styles, and 'defocused' mode causing
double-width lines.  

There was also graphical input mode (so called GIN), 
allowing user to specify position on screen using
cross-hairs controlled by two thumb-wheels on the keyboard
(no computer rodents at this time yet...). The cross-hairs
were displayed using low intensity beam, to weak to cause
permanent phosphors glow.

Along with graphics there was a text mode, but quite
limited by the same principles that made 4014 such 
successful in graphics - there was no way to replace a
character nor scroll the page. The text was overstriking,
or whole screen must been cleared.

The terminal was controlled using simple ascii control 
sequences. Typical single vector drawing command occupied
only 4 bytes. This allowed to work over slow serial lines,
and dramatically reduced host processor load. 

The great success of Tektronix 4014 opened the era of 
interactive computer graphics including the first CAD
systems. Support for Tektronix graphics was important
feature long time after the original equipment went out
of use. You can find it in Xterm, NCSA Telnet and DOS
Kermit packages.

The nice and probably overlooked use of Tektronix emulation
is possibility of generating graphics from Unix shell
servers accessible via telnet - like sdf-eu.org.