What is a digit?

A digit is one of the characters used in any positional numbering system to represent all numbers starting at 0 and ending at one less than the base of the numbering system. In the decimal system, there are ten digits, 0 – 9, and in the hexadecimal system there are sixteen digits, 0 – 9 and a – f.

A binary number system is one that uses only two digits, 0 and 1.

A hexadecimal number system is one that uses sixteen digits, 0 – 9 and a – f.