<P> An analog computer or analogue computer is a form of computer that uses the continuously changeable aspects of physical phenomena such as electrical, mechanical, or hydraulic quantities to model the problem being solved . In contrast, digital computers represent varying quantities symbolically, as their numerical values change . As an analog computer does not use discrete values, but rather continuous values, processes cannot be reliably repeated with exact equivalence, as they can with Turing machines . Unlike digital signal processing, analog computers do not suffer from the quantization noise, but are limited by analog noise . </P> <P> Analog computers were widely used in scientific and industrial applications where digital computers of the time lacked sufficient performance . Analog computers can have a very wide range of complexity . Slide rules and nomograms are the simplest, while naval gunfire control computers and large hybrid digital / analog computers were among the most complicated . Systems for process control and protective relays used analog computation to perform control and protective functions . </P>

What is the difference between digital computers and analog computers
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