This standard defines the universally recognized codes for county (or region). There are two alphabetic standards for country codes:
ISO-3166-1 Alpha-2 describes the two-letter codes.
ISO-3166-1 Alpha-3 describes the three-letter codes.
Country identifiers are specified as two or three uppercase ASCII letters. For example, US for United States and JP for Japan.
Language and country identifiers are combined into one string, connected by the underscore character. For example, en_US for English as used in the US, and ja_JP for Japanese as used in Japan.