Recent trends toward the application of microprocessor technology for the control of hydraulic systems have made it necessary for the Hydraulic Control Specialists to expand their skills to include this new technology. This paper has been written to introduce designers of Hydraulic Systems to the basic functional building blocks, so that they may understand and then utilize this relatively new technology. After a brief introduction and a comparison of the relative merits of analog and digital systems, the paper proceeds with a review of terminology. Then basic hardware and software components of a typical computer system are described. Finally, a typical semiconductor microcomputer is discussed, with emphasis on voltage, current levels and underlying logic.