the neon-orange plasma displays invented for the plato system in the late 01960s had an enormous, unique advantage for this kind of thing
they were bistable and switchable! so you could have a 512×512 display which had, in the physical display itself, 262144 bits of memory, equivalent to 32768 bytes. by contrast (heh), a lcd or normal crt fades in a second or two if you don't redraw it, which means you need a separate memory somewhere to hold the data to redraw, memory you have to run through many times a second in order to generate a steady display
the tektronix 4010 and 4014 graphics terminals (derived from the tektronix type 564 and the hughes aircraft company model 104d) had a similarly bistable crt, making it possible to do detailed high-resolution graphics at an affordable cost, but you couldn't erase pixels; you could only erase the whole screen
so normal plato users enjoyed multiple fonts, equations with superscripts and subscripts, and full-screen high-resolution graphics that users of other systems could only dream of, unless they had enough money to devote tens of kilobytes of ram to a framebuffer—which, of course, is precisely what the gas-plasma display inspired alan kay to lead a group at xerox parc to start doing, a few years later
(why didn't people use the plasma panels for computer ram? because they were slooow. updating a pixel took on the order of a millisecond. same reason they didn't use dekatrons or ne-3 lamps)
brian dear wrote a very interesting book about the history of the plato project
http://friendlyorangeglow.com/
