Reserved code elements are codes which, while not ISO 3166-1 codes, are in use for some applications in conjunction with the ISO 3166 codes. They are reserved to add flexibility to the coding system. Usually, obsolete codes may be kept as reserved, while some overseas territories, international organizations, and special nationality status have reserved codes of their own. See the corresponding sections in "ISO 3166-1 alpha-2" and "ISO 3166-1 alpha-3" for their respective reserved codes (ISO 3166-1 numeric does not have reserved codes).