A
grid of
dots used to create
pictures and/or
text.
Dot matrix printers used a grid of a certain size; the modern ink jet
and laser printers use the same principle, but a different mechanism for
delivering the ink to the paper, and a higher resolution.
All computer monitors are effectively dot matrix displays, using a grid
of 640x480 or 800x600 or 1024x768 or other size to display text and graphics.
Pinball machines in the 1990s used LED dot matrix displays to display scores and
game messages.
It is possible to use almost any grid of lights as a dot matrix display; this has been
done with the lights in windows of office buildings to create pictures, spell out
messages, play Tetris, etc.