In signal processing, an auio converter or digital audio converter is a type of electronic hardware technology which converts an analog audio signal to a digital audio format, either on the input (Analog-to-digital converter or ADC), or the output (Digital-to-analog converter, or DAC). They are common in numerous technologies —notably in computer sound cards, digital cellular phones, and portable recording devices. Once converted to digital format, digital audio signals and file formats can be processed in any of a number of ways as allowed by software —including converting to audio CD or Mp3 formats.