ABSTRACT
An important application of logic is in an arithmetic unit. This chapter develops the main components of an arithmetic unit and describes a simple system controller. It also develops an elementary programming language for operating this system. In arithmetic the process of subtracting one number from another has some similarity with addition. A digit by digit approach is used starting with the least significant digits. If the subtrahend is in two's complement code, then subtraction can be achieved with an adder circuit. In order to understand multiplication in a logic system, the method of arithmetical multiplication must be examined. Counter-based multipliers are totally unacceptable for high speed arithmetic. When designing logic systems to perform arithmetic, it is desirable to have a single system which can perform a number of different operations rather than a collection of different circuits, each of which only performs one operation.
