scope:

This part of ISO 639 provides four-letter representations (alpha-4) and language identifiers for language variants and a framework for relating them to languages, language families, and language groups. The alpha-4 representations have been developed for use in a wide range of applications, especially in computer systems, where there is a potential need to cover the entire range of languages, language families and languages as well as language variants within each identified language. Alpha-4 representations will support the quantity of known language variants and accommodate any future expansion. This part of ISO 639 provides a hierarchical framework, which facilitates backward compatibility with other ISO 639 codes, based on linguistic and/or geo-linguistic relationships, within which a comprehensive enumeration of language variants is possible, including living, extinct, ancient and constructed languages, whether major or minor. As a result, this part of ISO 639 caters for a very large number of languages and their variants. Registrations for languages designed exclusively for machine use, such as computer-programming languages and reconstructed languages will not be included in this standard.