The golden age of computers began with the digital revolution, but people have been using computers in their daily lives since the beginning of civilization. The history of computers began with simple adding devices. Milestones in the 20th century included the invention of the transistor and the development of the microprocessor, which led to the modern-day computer.

The first computers did not have electrical circuits, monitors or memory. The abacus, an ancient Chinese adding machine, is one of the original computing machines, used as early as 400 B.C. It can't do many of the computations that a modern electronic calculator can do, but it in the right hands it can make calculating large sums as easy as moving beads around. Famous mathematicians such as Leonardo da Vinci and Blaise Pascal invented more sophisticated calculators using gears and punch cards.

The invention of the vacuum tube in 1904 kicked off a revolution in computers. A vacuum tube is a tube that has had all air and gas removed, making it perfect for controlling electrical circuits. By using vacuum tubes together with hundreds or thousands of electrical circuits, a computer's vacuum tube can perform calculations by turning these circuits on (current flowing) or off (no current flowing). Computers from before 1950 often had vacuum tubes in their processors.

Developed by Bell Laboratories in 1947, transistors are made of a metal (usually silicon) that, like vacuum tubes, can switch circuits on and off. Current technology makes it possible to make transistors as small as a single molecule. This allows computer manufacturers to make microprocessors (the "brains" of the computer) small enough to fit in the palm of your hand but still capable of performing billions of calculations in a single second.

The most recent milestone in the history of computers has been the birth of the Internet and other networks. In 1973, Bob Kahn and Vint Cerf developed the basic idea of the Internet, a form of communication between different computers through packets of data. Tim Berners-Lee developed the World Wide Web, a network of Web servers, in 1991. A year later, the number of Internet "hosts" (computers connected to the Internet) exceeded one million.