ABSTRACT
The process of sampling a waveform, holding the value, and quantizing the value to the nearest number that can be digitally represented (as a specific integer on a finite range of integers) is called Analog to Digital (A to D, or A/D) conversion. A device which does A/D conversion is called an Analog to Digital Converter (ADC). Coding and representing waveforms in sampled digital form is called Pulse Code Modulation (PCM), and digital audio signals are often called PCM audio. The corresponding process of converting a sampled signal back into an analog signal is called Digital to Analog Conversion (D to A, or D/A), and the device is called a Digital to Analog Converter (DAC). Low pass filtering (smoothing the samples to remove unwanted high frequencies) is necessary to reconstruct the sampled signal back into a smooth, continuous time analog signal. This filtering is usually contained in the DAC hardware.
