Analog computer is a device that uses continuously changing quantities to model the behavior of a system being studied. Analog computers are contrasted with digital computers, which use quantities that change in noncontinuous “jumps” (see Digital technology).
Some analog computers are physical systems that behave in a similar way to a more complex system. For example, the 1949 Phillips Economics Computer, also called the Moniac, used flowing water to represent aspects of a nation’s economy, such as the money supply. Other analog computers are more versatile and can solve mathematical equations that describe the behavior of various systems.
Before electronics, the most common analog computers were mechanical. Such a computer may have included rotating discs, gears, and levers. The motions and positions of these could be measured, for example, to solve mathematical equations describing the flight path of an artillery shell.
Beginning in the mid-1900’s, as electronics became more common, most analog computers used electrical voltages. The voltages could represent such physical properties as force, temperature, motion, or pressure.
Electronic analog computers have largely been replaced by digital computers. But they are still used in some specialized applications. Analog computers are particularly useful when the system they model is harder to study than a model of that system. They are also useful when mathematical equations describing such systems are difficult to solve.
