analogue computer

Computing device that performs calculations through the interaction of continuously varying physical quantities, such as voltages (as distinct from the more common digital computer, which works with discrete quantities). An analogue computer is said to operate in real time (corresponding to time in the real world), and can therefore be used to monitor and control other events as they happen.

Although common in engineering since the 1920s, analogue computers are not general-purpose computers, but specialize in solving differential calculus and similar mathematical problems. The earliest analogue computing device is thought to be the flat, or planispheric, astrolabe, which originated in about the 8th century.