An analogue-to-digital converter, or simply ADC, is a semiconductor device that is used to convert an analogue signal into a digital code. In the real world, most of the signals sensed and processed by humans are analogue signals. Analogue-to-digital conversion is the primary means by which analogue signals are converted into digital data that can be processed by computers for various purposes.
   An analogue signal is a signal that may assume any value within a continuous range. Examples of analogue signals commonly encountered every day are sound, light, temperature, and pressure, all of which may be represented electrically by an analogue voltage or current. A device that is used to convert an analogue signal into an analogue voltage or current is known as a transducer. An analogue-to-digital converter is used to further translate this analogue voltage or current into digital codes that consist of 1's and 0's.
   A typical ADC, therefore, has an analogue input and a digital output, which may either be 'serial' (consisting of just one output pin that delivers the output code one bit at a time) or 'parallel' (consisting of several output pins that deliver all the bits of the output code at the same time).