A group of eight bits - that's eight binary digits - which is the usual form in which data is manipulated within a computer. One byte can hold numbers between 0 and 255. For example, each different letter of the alphabet, numeral and punctuation mark has a special code that describes it (see ASCII code). This code is stored within one byte, and so your computer can identify 256 different characters. (See also Kilobyte, Megabyte.)