The International Organization for Standardization (ISO) created and maintains the ISO 3166 standard – Codes for the representation of names of countries and their subdivisions. The ISO 3166 standard contains three parts:
ISO 3166-1 – Codes for the representation of names of countries and their subdivisions – Part 1: Country codes defines codes for the names of countries, dependent territories, and special areas of geographical interest. It defines three
sets of country codes:
ISO 3166-1 alpha-2 – two-letter country codes which are also used to create the ISO 3166-2 country subdivision codes and the Internet country code top-level domains.
ISO 3166-1 alpha-3 – three-letter country codes which may allow a better visual association between the codes and the country names than the 3166-1 alpha-2 codes.
ISO 3166-1 numeric – three-digit country codes which are identical to those developed and maintained by the United Nations Statistics Division, with the advantage of script (writing system) independence, and hence useful for people or systems using non-Latin scripts.
ISO 3166-2 – Codes for the representation of names of countries and their subdivisions – Part 2: Country subdivision code defines codes for the names of the principal subdivisions (e.g., provinces, states, departments, regions) of all countries coded in ISO 3166-1.
ISO 3166-3 – Codes for the representation of names of countries and their subdivisions – Part 3: Code for formerly used names of countries defines codes for country names which have been deleted from ISO 3166-1 since its first publication in 1974.
The ISO 3166-1 standard currently comprises 249 countries, 193 of which are sovereign states that are members of the United Nations. Many dependent territories in the ISO 3166-1 standard are also listed as a subdivision of their parent country in the ISO 3166-2 standard.