In the 19th century, computers walked the streets of England. Generations before the dawn of Windows, "computers" were people, employed to calculate and double-check endless tables of simple computations used by navigators, astronomers, and engineers.
The tedium of the work and the fallibility of the computers often resulted in tables teeming with errors. Errata sheets were issued for flawed tables, but they often contained errors of their own, necessitating the embarrassing step of issuing errata for errata.
In 1821, British mathematician Charles Babbage was cross-checking tables for use by the Astronomical Society. The numerous errors within the tables led him to exclaim: "I wish to God these calculations had been executed by steam!"
Babbage would soon see the potential for a mechanical calculating and printing machine that would act as an infallible mechanical mind, eliminating all errors of calculation with a single great technological leap.
"The Difference Engine" follows Babbage's quest to build the first mechanical computer. Author Doron Swade is the assistant director of London's Science Museum, and helped lead an attempt to build a complete Difference Engine to commemorate Babbage's 200th birthday in 1991. This puts the author in a uniquely sympathetic relationship with his subject. The struggles he suffered to build his modern machine neatly parallel those suffered by Babbage.
But while Swade seems consistently even-tempered, Babbage was as blunt and confrontational as he was brilliant. Much of "The Difference Engine" is devoted to the inventor's struggle to keep building the financially draining machines under withering attacks from his critics.
There was, however, some truth to the criticism of Babbage. Despite an enormous public subsidy, Babbage took few of his ideas from drawing board to completion. But for all their expense, his machines were remarkably prescient. His design for the Analytical Engine, for instance, had two major sections of machinery: One executed arithmetical operations, and the other stored the resulting numbers. Babbage called these clusters the "Mill" and "Store," but we know them today as "memory" and the "central processing unit." In short, Babbage created a mechanical model for the basic architecture of the modern computer.
However, a model was all it would ever become. His various designs for the Analytical Engine never left the drawing board. And while Babbage did manage to complete a portion of his more elementary Difference Engine, it never found a market; the machine was expensive, difficult to maintain, and computationally limited.
Babbage had even planned for a printing attachment that would output numbers onto notecards so the machine's limited mechanical memory could be extended by paper. Punch cards were used to determine the machine's calculations, an idea borrowed from the Jacquard loom, which used punch cards to weave incredibly complicated and subtle patterns.
Swade's writing is modest and reserved. He lets his bombastic and brilliant protagonist fill the pages with his struggle against the naysayers within the British scientific and political establishment. But Swade's candid account of his own struggles to build a Difference Engine is just as exciting.
Readers might think that modern know-how would make Babbage's labors easy to recreate and supercede. Swade tells a different story. An incredible amount of mechanical ingenuity and precision engineering is needed to breathe life into one of Babbage's clockwork beasts. A Difference Engine is a veritable forest of moving, interlocking parts, disturbingly prone to breaking and jamming.
Despite the sympathy between Swade and his subject, he plays down much of Babbage's practical intellectual impact. Swade describes how Babbage's sophisticated ideas had no real intellectual heirs. Not until after the basic principles of computing were well established, did Babbage's lifework begin to be revisited and celebrated.
But if Babbage was ultimately a failure as an inventor, an intellectual giant with shoulders no one stood upon, why sing his praises?
By telling Babbage's story, Swade tells a timeless tale of science. Babbage fought for the extension of mankind's knowledge in the face of a society motivated by short-term profit. He battled for ideas, not personal gain, and he sacrificed much of his own life to prove their essential truth. And while Babbage departed the world in bitter obscurity, he never lost faith in the potential for his engines to revolutionize computation.
Modern science enthusiasts will find much to love in this turbulent but ultimately inspiring story.
James Norton is news editor of the Monitor's online edition.
The Difference Engine: Charles Babbage and the Quest to Build the First Computer
By Doron Swade Viking 342 pp., $24.95