Country codes are short alphabetic or numeric geographicalcodes (geocodes) 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 3166-1. The term country code frequently refers to international dialing codes, the E.164country calling codes.
The Fédération Internationale de Football Association (FIFA) assigns a three-letter code (dubbed FIFA Trigramme) to each of its member and non-member countries: List of FIFA country codes
The North Atlantic Treaty Organisation (NATO) used two-letter codes of its own: list of NATO country codes. They were largely borrowed from the FIPS 10-4 codes mentioned below. In 2003, the eighth edition of the Standardisation Agreement (STANAG) adopted the ISO 3166 three-letter codes with one exception (the code for Macedonia). With the ninth edition, NATO is transitioning to four- and six-letter codes based on ISO 3166 with a few exceptions and additions.
the first few characters of call signs of radio stations (maritime, aeronautical, amateur radio, broadcasting, etc.) define the country: the ITU prefix,