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The concept of digital data manipulaTIon has made a dramaTIc impact on our society. Onehas long grown accustomed to the idea of digital computers. Evolving steadily from mainframeand minicomputers, personal and laptop computers have proliferated into daily life.More significant, however, is a conTInuous trend towards digital soluTIons in all otherareas of electronics. Instrumentation was one of the first noncomputing domains where thepotential benefits of digital data manipulation over analog processing were recognized.Other areas such as control were soon to follow. Only recently have we witnessed the conversionof telecommunications and consumer electronics towards the digital format.Increasingly, telephone data is transmitted and processed digitally over both wired andwireless networks. The compact disk has revolutionized the audio world, and digital videois following in its footsteps.The idea of implementing computational engines using an encoded data format is byno means an idea of our times. In the early nineteenth century, Babbage envisioned largescalemechanical computing devices, called Difference Engines [Swade93]. Althoughthese engines use the decimal number system rather than the binary representation nowcommon in modern electronics, the underlying concepts are very similar. The AnalyticalEngine, developed in 1834, was perceived as a general-purpose computing machine, withfeatures strikingly close to modern computers. Besides executing the basic repertoire ofoperations (addition, subtraction, multiplication, and division) in arbitrary sequences, themachine operated in a two-cycle sequence, called “store” and “mill” (execute), similar tocurrent computers. It even used pipelining to speed up the execution of the addition operation!Unfortunately, the complexity and the cost of the designs made the concept impractical.For instance, the design of Difference Engine I (part of which is shown in Figure 1.1)required 25,000 mechanical parts at a total cost of £17,470 (in 1834!).
