Hardware - Peripherals
Input Devices - Light Pen

A Light Pen is a pointing device shaped like a pen and is connected to a VDU.
The tip of the light pen contains a light-sensitive element which, when placed against the screen, detects the light from the screen enabling the computer to identify the location of the pen on the screen.

A light pen

Light pens have the advantage of 'drawing' directly onto the screen, but this can become uncomfortable, and they are not as accurate as digitising tablets.