By the late 1990s, personal computers (PCs) had found a place in millions of American homes. They were part of everyday life for office workers, as common as coffee cups and paper clips. Personal computers were used in all aspects of the media, in libraries, schools, and businesses of all kinds. Portable models had become a common sight on city streets, on public transport, and in cafes and bars. Yet barely twenty years earlier, PCs were available only to electronics hobbyists and the very rich. For most people in the 1970s, the personal computer was a device straight out of science fiction.

The PC revolution was made possible by the invention of the microprocessor—a computer chip that contains the entire central processing unit (CPU) of the computer. Before the late 1970s, computers were so large they had special rooms all to themselves. They needed a...