Computers these days spend a fairly low fraction of their time computing. In fact, the very word "computer" has become something of a misnomer. In the American History museum of the Smithsonian Institute in Wash- ington, D.C., there is an exhibit of early computers. Three features of these machines are striking. First, they are enormous, especially in com- parison to their capabilities. The museum visitor who has just come from the Natural History...