A number system based on 16, usually referred as "base 16." Each digit in a number essentially has 16 possibilities, comprising the numerals 0:15. In the hexadecimal system, as applied to computers, the digits 0:9 are utilized as is, the digits 10:15 representing the letters A:F. The hexadecimal system is widely used in computer applications, as it can be easily reduced to binary figures, and all 16 hexadecimal digits can be represented in four bits, two hexadecimal digits (each representing a set of four bits) can be stored in one byte of data. Many e-mail systems convert attached files to hexadecimal form for compact and rapid transmission over the Internet or other networks. Hexadecimal is usually abbreviated hex.