UN M49 or the Standard Country or Area Codes for Statistical Use (Series M, No. 49) is a standard for area codes used by the United Nations for statistical purposes, developed and maintained by the United Nations Statistics Division. Each area code is a 3-digit number which can refer to a wide variety of geographical and political regions, like a continent and a country. Codes assigned in the system generally do not change when the country or area's name changes (unlike ISO 3166-1 alpha-2 or ISO 3166-1 alpha-3), but instead change when the territorial extent of the country or area changes significantly,[1] although there have been exceptions to this rule.[a]
Some of these codes, those representing countries and territories, were first included as part of the ISO 3166-1 standard in its second edition in 1981, but they have been released by the United Nations Statistics Division since 1970.[4]
Another part of these numeric codes, those representing geographical (continental and sub-continental) supranational regions, was also included in the IANA registry for region subtags (first described in September 2006 in the now obsoleted RFC 4646, but confirmed in its successor RFC 5646, published in September 2009) for use within language tags, as specified in IETF's BCP 47 (where the ISO 3166-1 alpha-2 codes are used as region subtags, instead of UN M.49 codes, for countries and territories).
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