Analog computer

A form of computer using electronic or mechanical phenomena to model the problem being solved by using one kind of physical quantity to represent another.

Used in distinction to digital computers, in which physical or mechanical phenomena are used to construct a [finite-state machine]? which is then used to model the problem being solved.

Unlike digital computers, an analog computer does not have generalized computing power (see Church-Turing thesis) and is only useful for the problem it is configured to solve.

An example:

• the abacus is a hand-operated digital computer
• the slide rule is a hand-operated analog computer

Examples of analog computers:

• Tide predictors
• Mechanical integrators
• Target predictors
• Hydraulic model of UK economy
• and (trivially) the slide rule