International Standard Book Number
The International Standard Book Number (ISBN) is a unique numeric commercial book identifier based upon the 9-digit Standard Book Numbering (SBN) code created by Gordon Foster, Emeritus Professor of Statistics at Trinity College, Dublin, for the booksellers and stationers W. H. Smith and others in 1965.
The 10-digit ISBN format was developed by the International Organization for Standardization (ISO) and was published in 1970 as international standard ISO 2108. (However, the 9-digit SBN code was used in the United Kingdom until 1974.) An SBN may be converted to an ISBN by prepending the digit "0". ISO has appointed the International ISBN Agency as the registration authority for ISBN worldwide.
Since 1 January 2007, ISBNs have contained 13 digits, a format that is compatible with "Bookland" EAN-13s.
Occasionally, a book may appear without a printed ISBN if it is printed privately or the author does not follow the usual ISBN procedure; however, this can be rectified later.
Another identifier, the International Standard Serial Number (ISSN), identifies periodical publications such as magazines.