In telecommunication, the term alphanumeric has the following meanings:

1. Pertaining to a character set that contains letters, digits, and sometimes other characters, such as punctuation marks.

2. Pertaining to a set of unique bit patterns that are used to represent letters of an alphabet, decimal digits, punctuation marks, and other special signs and symbols used in grammar, business, and science, such as those displayed on conventional typewriter keyboards.

Source: from Federal Standard 1037C and from MIL-STD-188\n