Given how little most of us understand about the insides of our computers, the etchings on the silicon chips at their cores can look as cryptic and occult as the tracery on a shaman's vision stone. Danny Hillis, an alumnus of the MIT Artificial Intelligence Lab, founder of Thinking Machines, and now a researcher at Disney, wastes no time bemoaning this widespread ignorance about computers. Near the end of The Pattern on the Stone, in fact, he suggests that no one is smart enough to understand all the things computers can do. But Hillis nonetheless sets out to dispel the computer's undeserved mystique using a series of equally nimble comparisons.

There's nothing special about silicon, Hillis wants the reader to know. The universal building blocks of computation-simple, logical functions such as "and," "or," and "not"-can be implemented using rods and springs, water pipes and hydraulic valves, and many other physical systems. All decisions can be broken down into combinations of these simple functions, and computer programs are simply vast trees made up of such decisions. Hillis goes on to explain, plainly and concisely, how programming languages, algorithms and heuristics, memory and encryption, and other arcana are abstractions building upon each other and on the basic building blocks.