The premise of this book is that computing, per se, has a rich history that precedes and leads up to the efforts to create an electronic stored-program digital computer at the Moore School of the University of Pennsylvania in 1945. The authors, all historians, believe that only by understanding what preceded the computer can we truly appreciate it. The chapters of this book trace several distinct older traditions that converged to produce today’s computer technology. The material is written for a general audience and relates each technology to the intellectual, social, and institutional contexts of its time.

The first chapter, on “Early Calculation,” is by Michael R. Williams of the University of Calgary. Williams starts by discussing the abacus, which formed the basis of calculation until the middle of the sixteenth century, when John Napier invented his “calculating bones.” Napier also invented logarithms, which became the basis for the slide rule (which was used widely in scientific and engineering circles until the 1960s). The discussion then proceeds to mechanical calculating machines, starting with those of Schickard, Pascal, and Leibniz. Williams concludes with a discussion of nineteenth- and twentieth-century developments such as Thomas’s Arithmometer, The Felt and Tarrant Comptometer, and the Brunsviga calculating machine.

Chapter 2, “Difference and Analytical Engines,” is by  Allan  G. Bromley of the University of Sydney. Bromley discusses the life of Charles Babbage (born on December 26, 1791) and his efforts to create a machine to do calculation. The discussion starts with the project to build a “difference engine,” contains an in-depth discussion of the “analytical engine,” and concludes with the Scheutz difference engine, which was actually manufactured and offered for sale (a copy of the Scheutz engine is included in the “Information Age” exhibit at the Smithsonian Institution).

Chapter 3, by William Aspray of the IEEE, discusses “Logic Machines.” Aspray begins with a discussion of “automata,” that is, devices built to mimic the physical and mental aspects of human behavior. Interest in logic machines per se began with Charles Stanhope in the late 1700s and continues to the present. Luminaries such as Claude Shannon and Alan Turing have done research in this field.

The fourth chapter, “Punched-card Machinery,” by Martin Campbell-Kelly of the University of Warwick, starts with a discussion of the development of census machinery. With a growing population and a growing interest in population statistics, the US Census Bureau needed a better way to enumerate the census of 1890. Herman Hollerith, who had worked for the Census Bureau from 1879 to 1882, had developed and patented mechanical devices to read punched tape and cards. He won a competition staged by the Bureau, and developed a range of equipment for the mechanical tabulation of the 1890 census. Hollerith’s efforts led to the development of the electronic accounting machine industry.

In chapter 5, Bromley provides us with another antecedent technology, “Analog Computing Devices.” Simple analog devices have been with us since antiquity. Many of these, such as the Antikythera device, were models of the heavens or were used to tell time. The development of analog devices continued through the 19th and 20th centuries, and resulted in a variety of planimeters, tide predictors, and harmonic analyzers. The problem of calculating continuous engineering functions led Vannevar Bush to develop the Differential Analyzer, which served as a model for electrical analog computers, some of which are still in use today.

Paul E. Ceruzzi, of the Smithsonian’s National Air and Space Museum, discusses “Relay Calculators” in chapter 6. By the 1930s, a number of inventors recognized that electrical components, such as the telephone relay, could be used to build calculating devices. Ceruzzi describes the work of three of the most famous: Konrad Zuse, George Stibitz, and Howard Aiken. Although their efforts were eclipsed by the faster-acting vacuum tubes, relay computers played an important role in the development of automatic sequenced calculation.

The final chapter, also by Ceruzzi, examines “Electronic Calculators.” While Zuse, Stibitz, and Aiken were experimenting with relays, others looked to vacuum tubes as ideal devices for the construction of calculating devices. Ceruzzi starts by looking at the work of John V. Atanasoff at Iowa State, Helmut Schreyer’s work in Berlin, and the work done in Britain on the Colossus. The chapter concludes with a discussion of the work of Presper Eckert and John Mauchly at the University of Pennsylvania on the Electronic Numeric Integrator and Computer (ENIAC).

Taken together, these chapters identify seven streams of thought and invention. Each evolved from the spark of an idea into useful devices. Each played a role in the continuing idea of automatic machine computation. Each contributed to the development of the electronic stored-program digital computer. In an era when technology surrounds us, and when manufacturers are hawking palm-top computers, it is easy to forget how new this technology is. Few of us remember what it was like before computers; this superb volume attempts to rectify that vacuum.