A BASIC computer program was written for an experiment that measures the time of a fall of a ball-bearing dropped through a measured distance. However, the timing subroutine was written in machine language. The reason for using machine language, the machine language program, hardware used, and the experiment are discussed. (JN)

A 16K Sinclair ZX81 microcomputer equipped with an analog to digital board and a Sinclair printer was used to capture data continuously from a total of eight temperature or light sensors. Describes the construction of the peripherals, explains how to connect them together, and provides a program to run the ZX81. (Author/JN)