Microcomputers are commonly interfaced to external devices in scientific, industrial, and consumer settings for data acquisition and for control. The general problem under consideration is the task of taking measurements of some continuous phenomenon, transforming them into digital form, and storing the data in the microcomputer for later use. First, the physical variable to be measured must be changed to a voltage (or resistance) by means of some transducing device; for example, light intensity can be transduced to a voltage using a photocell. Then, too-large or too-small voltages need to be amplified. Next, the continuous voltage is converted to a digital representation in eight bits. Finally, the analog-digital converter is connected to the data address, and control buses of the microcomputer. Microcomputers such as Apple, TRS-80, Atari, Compucolor, and others, have a "game paddle" which is used to accomplish all of these steps while another method involves using a thermocouple. Once the system is ready, such experiments as those involving pendulums can be easily accomplished, a typical program recording the position of a swinging pendulum, displayed the motion on the monitor, and displaying graphs of variables examined during the experiment. Most students prefer using the computer as it swiftly and accurately performs the experiment's busywork. (Author/JN)