Although semiconductors and microchips are essential components of modern computers, many people do not realize that computing machinery does not really need to be constructed with components that are normally associated with electronic equipment. In fact, some of the earliest computers were purely mechanical machines—they did not rely on electrical technology at all. For example, Charles Babbage's Analytical Engine, designed in 1834 at a time when the use of electricity was in its infancy, was a purely mechanical machine. Had Babbage actually been able to build it, his Analytical Engine would have been a bona fide computing machine.

Similarly, many of the early computers and calculators were mostly mechanical, using carefully constructed linkages, levers, and cogs. It is important to note that the technology used to implement computers does not define them. Instead, machines are termed computers if they are programmable—regardless of the...