"Analog to Digital", or A/D, is the operation that transforms a real-world signal into a digital signal and it is achieved by combining sampling and quantization. Conversely, "Digital to Analog", or D/A, is the operation that, by combining an inverse quantization with an interpolator, produces an analog continuous-time signal from a digital sequence.

These operations, being at the interface between the digital and analog domains, are not simple "algorithms" but must be implemented by specialized hardware.

In this optional lesson, we will briefly look (in simplified terms) at the electronic circuits that are at the heart of the inexpensive, commercially available A/D and D/A converters.