Digital data

In information theory and information systems, digital data is information that is represented as a string of discrete symbols. Each symbol in the string may only take on one of a limited number of values derived from some alphabet, such as letters or digits. A text document is a good illustration of this concept since it is made up of a series of alphabetic and numeric characters. In contemporary information systems, binary data is the most prevalent kind of digital data. This type of data is represented by a string of binary digits (bits), each of which may have one of two values, either 0 or 1.

Analog data, on the other hand, is represented by a value that falls somewhere within a continuous range of real numbers. Digital data and analogue data may be compared with one another. An analogue signal is used to transport analogue data, and an analogue signal not only takes on continuous values but also may fluctuate continuously with time, making it a continuous real-valued function of time. Analog data is sent using analogue signals. One illustration of this is how the air pressure varies along the path of a sound wave.

Because counting is most often done with the fingers, the origin of the term digital is the same as that of the words digit and digitus, which is the Latin word for finger. In 1942, a mathematician working for Bell Telephone Laboratories named George Stibitz coined the term "digital" to describe the rapid electric pulses that were produced by a gadget that was intended to aim and fire anti-aircraft weapons. The phrase is most often used in the fields of computers and electronics, particularly in situations in which information from the real world is transformed into a binary numeric form, such as in digital audio and digital photography.

There are three states that data may exist in when it is stored digitally: data at rest, data in transit, and data being used. The data's confidentiality, integrity, and availability need to be maintained during its entire lifespan, from the moment the data is "born" until the moment it is deleted.