ISO 4217 "ruble". In addition to codes for most active national currencies ISO 4217 provides codes for "supranational" currencies, procedural purposes, and several things which are "similar to" currencies: The use of an initial letter "X" for these purposes is facilitated by the ISO 3166 rule that no official country code beginning with X will ever be assigned. Because of this rule ISO 4217 can use X codes without risk of clashing with a future country code. ISO 3166 country codes beginning with "X" are used for private custom use (reserved), never for official codes. For instance, the ISO 3166-based NATO country
ISO/IEC JTC 1/SC 22 ISO/IEC JTC 1/SC 22 ISO/IEC JTC 1/SC 22 Programming languages, their environments and system software interfaces is a standardization subcommittee of the Joint Technical Committee ISO/IEC JTC 1 of the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC) that develops and facilitates standards within the fields of programming languages, their environments and system software interfaces. ISO/IEC JTC 1/SC 22 is also sometimes referred to as the "portability subcommittee". The international secretariat of ISO/IEC JTC 1/SC 22 is the American National Standards Institute (ANSI), located in the United States. ISO/IEC JTC 1/SC 22 was created in 1985, with