Alphanumerics

Alphanumerics are characters drawn from the combination of letters and digits: the 26 Latin letters in uppercase, the 26 in lowercase, and the ten digits 0–9. The term is used to describe strings composed only of these characters, excluding punctuation and other symbols. The name derives from alpha and numeric.

In computing, alphanumeric strings are common for identifiers, usernames, file names, product codes, and serial numbers. They allow more variety than numeric-only data while avoiding locale-specific punctuation. Examples: A1B2C3, X9Y8Z7.

Encoding: In ASCII, alphanumeric characters occupy 62 code points (A-Z, a-z, 0-9). Unicode expands support to many scripts; most modern systems use UTF-8, where these characters are encoded with one to several bytes depending on the code point. Case sensitivity matters; 'A' and 'a' are distinct in most contexts.

Handling and considerations: Validation rules may require only alphanumeric characters; sorting may use lexical vs natural/alphanumeric sort. In security, alphanumeric constraints in passwords reduce possible characters; combining symbols increases entropy. Data validation for alphanumeric input helps with data integrity and search indexing.