The digital computer is a programmable electronic device that processes numbers and words accurately and at enormous speed. It comes in a variety of shapes and sizes, ranging from the familiar desktop microcomputer to the minicomputer, mainframe, and supercomputer. The supercomputer is the most powerful in this hierarchy and is used by organizations such as NASA to process upwards of 100 million instructions per second. The impact of the digital computer on society has been tremendous; in its various forms, it is used to run everything from spacecraft to factories, healthcare systems to telecommunications, banks to household budgets. The story of how the digital computer evolved is largely the story of an unending search for labor-saving devices. Its roots go back beyond the calculating machines of the 1600s to the pebbles (in Latin, calculi) that the merchants of Rome used for counting, to the abacus of the...