A Brief History of Personal Computers

A Brief History of Personal Computers

The electronic computer is a relatively modern invention; the first fully operable computer was developed about 50 years ago, at the end of World War II, by a team at the University of Pennsylvania's Moore School of Engineering. This team was headed by John Mauchly and J. Presper Eckert, who named the new machine ENIAC, for Electronic Numerical Integrator and Calculator. ENIAC was hardly a personal computer, occupying a large room and weighing about 33 tons. By today's standards, ENIAC was extremely slow, unreliable, and expensive to operate. In 1945, on the other hand, it was considered a marvel.

Over the next 30 years, computers became smaller, faster, and less expensive. However, most of these machines remained isolated in their own air-conditioned rooms, tended by specially trained personnel. By 1975, computers were in great demand at universities, government agencies, and large businesses, but relatively few people had ever come face-to-face with an actual computer. This all began to change in the late 1970s.

To understand why, let's take a closer look at the early computers. ENIAC and its immediate successors were large, slow, and unreliable primarily because they used thousands of large, slow, and unreliable vacuum tubes in their electronic circuits. The vacuum tubes were glass cylinders, typically about four inches high and an inch in diameter, which generated a lot of heat and thus could not be placed too close together. Then, in 1947, a momentous event occurred at Bell Labs - William Shockley, John Bardeen, and Walter Brattain announced the invention of the transistor. Only about an inch long and a quarter inch across, a transistor produced very little heat, and did the same job as a vacuum tube.

The downsizing of computers began in the 1950s as transistors replaced vacuum tubes, and continued into the 1960s with the introduction of the integrated circuit (IC) - an ice cube-sized package containing hundreds of transistors. By the late 1960s, microchips, consisting of thousands of electronic components residing on a piece of silicon the size of a postage stamp, had begun to replace ICs. At this time, some minicomputers occupied a space no larger than a small filing cabinet and cost less than $25,000. Then, in 1970, Marcian Hoff, Jr., working at Intel Corporation, invented the microprocessor, a central processing unit on a chip. The technological world was now ready for the personal computer.

The First Personal Computer