When you are firing out at night, the red tracers go out into the blackness as if you were drawing with a light pen.
Made of fine and light pen steel, and works as well in shirt sleeves as with a coat on.
A light pen held against a particular part of the display pattern can be used to signal the computer.
The light-spot cursor and joy-stick method replace the light pen in this case.
An early pointing device which the user pointed at a raster-scanned display screen. A photocell in the pen detected the flying spot of the raster scan. The position of the spot at that instant, obtained from the scanning electronics, was made available to software as (x, y) co-ordinates.