Country codes are short alphabetic or numeric codes developed to represent countries and dependent areas, for use in data processing and communications. Several different systems have been developed to do this. The most famous of these is ISO 3166. ISO 3166 defines two and three-letter country codes, and three-digit numeric codes, for most of the countries and dependent areas in the world. The two-letter codes from ISO 3166 are used as the basis for country code top-level domain names (ccTLDs) on the Internet. (If you are looking for a list of country codes used on the Internet, see Internet ccTLDs.)
Other country coding systems in use include the FIPS two-letter country codes used by the US government and in the CIA World Factbook, the coding system for car licenses plates under the 1949 and 1968 United Nations Road Traffic Conventions, and the E.164 international dialling codes developed by the ITU.
The developers of ISO 3166 intended that in time it would replace other coding systems in existence. It is used as the basis for many other standards, in areas such as currency codes, bank account numbers, securities numbers and location coding.