screen blanker

screen saver
phosphor fatigue
screen blanker

   <tool> A program which displays either a completely black
   image or a constantly changing image on a computer monitor to
   prevent a stationary image from "burning" into the phosphor of
   the screen.  Screen savers usually start automatically after
   the computer has had no user input for a preset time.  Some
   screen savers come with many different modules, each giving a
   different effect.

   Approximately pre-1990, many {cathode ray tubes}, in TVs,
   computer {monitors} or elsewhere, were prone to "burn-in";
   that is, if the same pattern (e.g., the {WordPerfect} status
   line; the {Pong} score readout; or a TV channel-number
   display) were shown at the same position on the screen for
   very long periods of time, the phosphor on the screen would
   "fatigue" and that part of the screen would seem greyed out,
   even when the CRT was off.

   Eventually CRTs were developed which were resistant to burn-in
   (and which sometimes went into {sleep} mode after a period of
   inactivity); but in the meantime, solutions were developed:
   home video game systems of the era (e.g., Atari 2600s) would,
   when not being played, change the screen every few seconds, to
   avoid burn-in; and computer screen saver programs were
   developed.

   The first screen savers were simple screen blankers - they
   just set the screen to all black, but, in the best case of
   {creeping featurism} ever recorded, these tiny (often under 1K
   long) programs grew without regard to efficiency or even basic
   usefulness.  At first, small, innocuous {display hacks}
   (generally on an almost-black screen) were added.  Later, more
   complex effects appeared, including {animations} (often with
   sound effects!) of arbitrary length and complexity.

   Along the way, avoiding repetitive patterns and burn-in was
   completely forgotten and "screen savers" such as {Pointcast}
   were developed, which make no claim to save your monitor, but
   are simply bloated {browsers} for {push media} which
   self-start after the machine has been inactive for a few
   minutes.

   (1997-11-23)