A digital system uses discrete values, usually but not always symbolized numerically to represent information for input, processing, transmission, storage, etc. By contrast, in a non-digital, or analog device, the systems use a continuous range of values to represent information. Although digital representations are discrete, the information represented can be either discrete, such as numbers, letters or icons, or continuous, such as sounds, images, and other measurements of continuous systems.

The word digital is most commonly used in computing and electronics, especially where real-world information is converted to binary numeric form as in digital audio and digital photography. Such data-carrying signals carry electronic or optical pulses, the amplitude of each of which represents a logical 1 (pulse present and/or high) or a logical 0 (pulse absent and/or low).