Dictionary of Computers - light pen

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Device resembling an ordinary pen, used to indicate locations on a computer screen. With certain computer-aided design (CAD) programs, the light pen can be used to instruct the computer to change the shape, size, position, and colours of sections of a screen image.

The pen has a photoreceptor at its tip that emits signals when light from the screen passes beneath it. From the timing of this signal and a gridlike representation of the screen in the computer memory, a computer program can calculate the position of the light pen.

The colours of the flag date from Napoleon's invasion in 1796. The design is based on the French tricolour. Effective date: 19 June 1946. >>