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 1966.

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'. Currently, the ISO's TC 46/SC 9 is responsible for the ISBN. The ISO on-line facility only refers back to 1978.

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.

A similar numeric identifier, the International Standard Serial Number (ISSN), identifies periodical publications such as magazines.

John David Barrow FRS (born 29 November 1952, London) is an English cosmologist, theoretical physicist, and mathematician. He is currently Research Professor of Mathematical Sciences at the University of Cambridge. Barrow is also a writer of popular science and an amateur playwright.

Barrow obtained his first degree in mathematics and physics from Van Mildert College at the University of Durham in 1974. In 1977, he completed his doctorate in astrophysics at Magdalen College in the University of Oxford under Dennis William Sciama. He did two postdoctoral years in astronomy at the University of California, Berkeley.

In 1981 he joined the University of Sussex and rose to the rank of Professor. In 1999, he became Professor in the Department of Applied Mathematics and Theoretical Physics and a fellow in Clare Hall at Cambridge University. He is Director of the Millennium Mathematics Project. From 2003–2007 he was Gresham Professor of Astronomy at Gresham College, London, and he has been appointed as Gresham Professor of Geometry from 2008–2011; only one person has previously held two different Gresham chairs. In 2008, the Royal Society awarded him the Faraday Prize.