One of the most highly publicized achievements of the past few years has been the development of high-speed digital computers, often mistakenly referred to as electronic "brains." Although it is not our purpose to give a detailed description of the design or operation of such computers, it is appropriate to conclude the discussion on the algebra of circuits with specific mention of some of the circuit-design problems which arise in their construction. Among the features of a computer which must be designed are devices by which information and instructions can be given to the machine, devices by which the machine can carry out these instructions and perform a variety of specialized tasks, and devices by which the results of the machine's efforts can be made available to the operator. Each of these areas has its own special types of circuit-design problems. The second area is the one which is probably of most interest to the novice. For this reason, we have included this chapter on some of the basic circuits capable of performing the simple arithmetic operations of addition, subtraction, and multiplication. It is hoped that these few brief sections will stimulate the reader to pursue the subject further in one of the several available books which treat computer design in considerable detail.

Before we can design circuits that can compute with numbers, it is necessary to discuss ways in which numbers may be represented by circuit elements. Any such method depends, in turn, upon some coding scheme for designating numbers. Many different coding methods are employed,  but probably the simplest one of all to understand is based upon the binary number system. The next section introduces this system.