16 Jun
2023
16 Jun
'23
10:08 p.m.
On 6/15/23, segaloco via COFF <coff(a)tuhs.org> wrote:
So terminals, they started as typewriters with extra steps, a white piece of
paper on a reel being stamped with dark ink to provide feedback from the
machine. When video terminals hit the market, the display was a black screen
with white, orange, green, or whatever other color of phosphor they bothered
to smear on the surface of the tube. Presumably this display style was
chosen as on a CRT, you're only lighting phosphor where there is actually an
image, unlike the LCD screens of today. So there was a complete contrast
shift from dark letters on white paper to light letters on an otherwise
unlit pane of glass.
The phosphors on CRT screens don't last forever. You only want to
light them when necessary. CRTs also suffer from the problem of
burn-in. If you keep the same picture illuminated for a long period
of time that pixel pattern gets burned into the phosphors. This is
why the later GUI CRTs had screen saver software that displayed an
ever-changing picture to prevent burn-in. This isn't a problem with
the modern, non-cathode-ray displays. Good ol' flying toasters.
-Paul W.