CRT displays [was: computer graphics in the 1950s]

[Tony Duell]

> The Datapoint 2200 used a serial mos memory in its first incarnation. 
> Sweeping each row of text implies scanning the same characters seven 
> times in a row.  They couldn't afford to add a line buffer, so they 
> invented "diddle scan".
> 
> They actually scan to the upper left corner of each character, then 
> sweep out the 5x7 dot matrix for that character, before adjusting the 
> x,y deflection to the upper left corner of the next character.

I seem to recall the DEC VT11 (and thus GT40) did something similar. When 
it displayed a character it scanned a little raster at the appropriate 
place on the screen and used a normal dot-matrix character generator to 
turn the beam on and off.

The HP1350, though, had a set of ROMs that were tables of the vector 
movements needed for each character. It didn't scan a raster for each 
character.

-tony