This standard is restricted to living languages
that are national or official languages and in which, therefore, written material is
regularly published.
The alpha-2 codes are written in lowercase only,
comprising characters from the set [a to z]. There is another part of the standard, ISO 639-2, that
consists of three-letter codes for languages. All languages with two-letter codes also
have three-letter codes.
The registration authority for ISO 639 is:
Infoterm, Österreichisches Normungsinstitut (ÖN), Postfach 130, A-1021 Wien, Austria.