since a computer is an electronic device, it operates at a speed comparable to the speed of electron flow. A medium-sized computer, for example, can perform 500000 addition in second that is, one every two-millionths of a second. The speed of operation of a computer is thus measured in microseconds or even in nanosecond (a nanosecond is one billionth of a second). At such speeds, a computer can solve in less than a minute problems that would take at last ten hours on a punched-card data processing system.