The Difference Engine: Charles Babbage and the Quest to Build the First Computer by Doron Swade, Viking, $24.95, 342 pages. Reviewed in the Chapel Hill News on March 10, 2002.

The Chapel Hill News


March 10, 2002

Calculated obsession


By Phillip Manning

By many measures, Charles Babbage was a failure. He spent his life trying to build two computers and never got either one of them off the drawing board. In the process, he wasted 17,000 £ of the British treasury's money (about the cost of two battleships). The dismal outcome of his life's work embittered him. Just before his death in 1871 at age 80, a friend reported that Babbage "spoke as if he hated mankind in general."

History has not been kind to Babbage. He was an accomplished mathematician, but until recently, his contributions to computer science were unfairly overshadowed by his beautiful but flakey aide, Ada Byron, the Countess of Lovelace and the daughter of Lord Byron. In "The Difference Engine" (Viking, $24.95), Doron Swade, of the Science Museum in London, sets the record straight. He recounts Babbage's magnificent but failed quest to build the world's first computer, and then, proving that obsessions can be contagious, he built the machine himself.

Babbage's computer dreams started with a problem. In the early 19th century, builders, merchants and others relied on tables for the numbers required in their work. Navigators, for example, depended on tables of astronomical data. The manually calculated tables were unwieldy, but, more importantly, they were inaccurate. These errors caused serious problems, especially in navigation where sailors' lives depended on accuracy. The Chancellor of the Exchequer said, "an undetected error in a . . . table is like a sunken rock at sea . . . upon which it is impossible to say what wrecks may have taken place."

Babbage himself laboriously checked many existing tables by hand and found them full of errors. Babbage began to design a machine that could perform complex mathematical calculations. He devised a system of levers, wheels, gears and shafts for a mechanical computer. After a decade of great expense and work, a demonstration piece -- a prototype of a computer that Babbage named the Difference Engine -- was delivered in 1832. It was, Swade writes, "a weighty bronze and steel embodiment of solidity and precision." And it could calculate, too, following simple instructions programmed into it by Babbage.

The Difference Engine prototype turned out to be the high point of Babbage's career. Thousands of parts for the full-scale machine were made but never assembled. Babbage had moved on to a new design, this one for a far more sophisticated machine than the Difference Engine. It was called the Analytical Engine, and it had the same basic elements as today's electronic computers. Data and programs would be entered on punched cards. The Mill (or CPU) performed arithmetical operations, and the Store (or memory) retained the results for output or further operations. This architecture is identical to that specified in 1945 by John von Neumann, who is regarded as the father of the modern computer.

Ada Lovelace met Babbage at a party in his London house and was entranced by his "thinking machine." Ada had a false sense of her own genius. "I have perceptions of things, which no one else has," she wrote and "immense reasoning faculties." However, despite studying mathematics for years, she was unable to solve even simple trigonometry problems. Nevertheless, she wanted to work with Babbage on the Analytical Engine.

Babbage had presented his ideas for the engine two years earlier at a scientific conference. One of the participants published a paper in French describing Babbage's ideas. Ada decided to translate the paper for publication in a British journal. Babbage encouraged her; he hoped that having a celebrity involved might help him get another grant from the British government. In 1843, 10 years after her meeting with Babbage, Ada published her translation. It was accompanied by seven "Translator's Notes," which ran about three times longer than the original paper and had a mystical tone that has endeared Ada to later generations.

Despite the publicity accompanying Ada's paper -- her only scientific publication -- the British government refused to sink any more money into Babbage's schemes. Today, Ada Lovelace has a computer language named after her and is celebrated in some circles as the first computer programmer. But until recently, Babbage was largely forgotten.

That situation changed when Doron Swade and his colleagues discovered Babbage's blueprints for the Difference Engine and decided to do what Babbage never could -- build the full-scale machine. They finished it in 1992, a few days before Babbage's 200th birthday. They tested it by raising 100 numbers to the power of seven, a feat that would require days to do manually. The machine performed flawlessly. The publicity accompanying its construction and testing generated numerous articles about Babbage, many of which proclaimed him as the father of modern computing.

Today, the gleaming Difference Engine sits on the floor of the London Science Museum, a proud monument to Babbage's magnificent obsession.

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