The International Standard Book Number ISBN) is a unique identifier for a book. The ISBN system was created in the United Kingdom in 1966 and adopted as the international standard in 1970. Each edition and variation (except reprints) of a book receives its own number consisting of codes for the country of origin, the publisher, the item number, and a checksum digit. The different parts can have different lengths and are usually separated by hyphens. The publisher number is assigned by the national ISBN agency, and the item number is chosen by the publisher. The ISBN number of a book is useful when trying to locate a book to purchase or borrow from a lending library. Because of a pending shortage in certain ISBN categories, the international standards organization will soon change the ISBN to a thirteen digit number. This move will also bring the ISBN system into line with the UPC barcode system.