ISO 3166: Codes for the Representation of Names of Countries (ISO 3166) is prepared by the International Organization for Standardization. ISO 3166 includes two- and three-character alphabetic codes and three-digit numeric codes that may be needed for activities involving exchange of data with international organizations that have adopted that standard. Except for the numeric codes, ISO 3166 codes have been adopted in the US as FIPS 104-1: American National Standard Codes for the Representation of Names of Countries, Dependencies, and Areas of Special Sovereignty for Information Interchange.

Internet:  The Internet country code is the two-letter digraph maintained by the International Organization for Standardization (ISO) in the ISO 3166 Alpha-2 list and used by the Internet Assigned Numbers Authority (IANA) to establish country-coded top-level domains (ccTLDs).