The Building Blocks
Michael G. Hartley, M. Healey, Peter G. Depledge · 1988
A digital computer is an interconnected network of logic circuit elements. Different features of the machine are created by specific combinations of the basic elements. These elements, the building blocks, are discussed in this chapter. Some specific examples of building blocks such as a binary adder and a counter are provided. A complete computer is left to chapters 5 and 6. It is most important for the reader to understand the concepts introduced here since they will be used freely in constructing more complete computer systems in later chapters. The fundamental elements of combinational logic , AND, OR, NOT, NAND and NOR gates, are described from a black-box viewpoint, rather than an electronic one, in keeping with the current trend towards widespread use of integrated circuits. Sequential logic elements with memory capability which comprise the various forms of flip-flop, are developed from combinational logic gates. The algebra of logic, Boolean algebra , is introduced together with truth tables . Only sufficient depth to help promote basic understanding is provided. The concept of data flow is stressed, an idea which is fundamental to the understanding of computer operation.