An analog computer is a system that provides information in continuous form. These computers can only represent physical quantities such as pressure, weight, voltage pressure, speed, and more.

At one time a scientist or engineer trying to solve a tough problem with electronic computation had the choice of an analog computer, a digital computer, or both together in a hybrid configuration.

Analog computers have been used extensively in the past, for things like tide calculations, but in the semiconductor era things have mostly gone digital. Even where you have analog elements, like DRAM ...