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 29 Greece, Hong Kong, Indonesia, Islamic Republic of Iran, Ireland, Malaysia, Morocco, Norway, Romania, Serbia, Slovakia, South Africa, and Turkey. ISO/IEC JTC 1/SC 29 currently has 541 published standards within the field of coded representation of audio, picture, multimedia, and hypermedia information, including: ISO/IEC JTC 1/SC 29 ISO/IEC JTC 1/SC 29 Coding of audio, picture, multimedia and hypermedia information 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 international standards, technical reports, and technical specifications within the field of audio, picture,