Alphanumeric, also called alphameric, is the set of letters of the alphabet and numeric characters from 0 through 9. It is a term used to describe any subset formed from this collection of symbols. Alphanumeric is also regarded as the combination of Latin letters and Arabic digits.
The term alphanumeric does not include punctuation and mathematical symbols. It is commonly used as the required format in creating passwords and file names. The string of characters “aBc123” is alphanumeric, but “#s?34T” is not.
Alphanumeric characters in the POSIX/C locale consist of either 36 case-insensitive symbols (A-Z and 0-9) or 62 case-sensitive characters (A-Z, a-z and 0-9).