What are examples of alphanumeric characters?

Alphanumeric characters are the letters of the alphabet (A-Z) and the numerals 0-9.

Ciphers or code-numbers which mix letters (alpha) and numbers (Numeric) examples, mostly military, wouold include M-l6 (an assault rifle), B-29 (a Bomber) G-2 (genrric term for intelligence) and so on... note mixing of letters and numbers. Many Library call numbers (In NYC) are of this type.