An accurate millisecond timer for the Commodore 64 or 128

The use of the Commodore 64 or 128 as an accurate millisecond timer is discussed. BASIC and machine language programs are provided that allow the keyboard to be used as the response manipulandum. Modifications of the programs for use with a joystick or external switches are also discussed. The precision, flexibility, and low cost of these machines recommends their use as laboratory instruments.