The ISBN is an identifier used to distinguish the publisher, title, edition and format of a product. This number is used by libraries, publishers, bookstores and online retail stores.
ISBN codes are assigned to items such as books, pamphlets, maps, audio-books of any format and educational or instructional videos and films. Magazines, newspapers and journals do not require an ISBN.
There are four parts to an ISBN, each separated by a hyphen: the group or country identifier, publisher identifier, title identifier and the check digit. The check digit is used to validate the ISBN.
The ISBN underwent changes in 2007 when it began requiring 13 digits instead of the former 10 digits. This change was necessary due to a shortage of ISBN codes in some countries and to standardize the product identifier. These new codes begin with a prefix of "978." Once those prefixes are all assigned, the prefix "979" will be used.
During the transition phase between ISBN-10 and ISBN-13, products were printed with both the 10- and 13-digit ISBN. After Jan. 1, 2007, the ISBN referred to the 13-digit code and the ISBN-10 began its phase-out.