Gordon Foster gave books a 9-digit code for W.H. Smith's computer

In 1965, W.H. Smith, then the largest book retailer in Great Britain, announced plans to move its warehouse operations onto a computerized inventory system within two years — a major modernization effort for a book trade that had always identified individual titles by name, author and edition in ordinary prose. That worked well enough for a human employee browsing a shelf, but a computer system needed something far more precise and consistent to reliably track and reorder specific books.

The British book trade convened working groups, including the Publishers Association's Distribution and Methods Committee, to design a solution, and the resulting numbering method came to be closely associated with Gordon Foster, then an academic statistician at Trinity College Dublin who had been drawn into the project.

The result was the Standard Book Number (SBN), a 9-digit code assigned uniquely to each book, with specific digits reserved to identify the publisher and the exact edition, plus a final check digit to catch transcription errors — completed in 1966 and put into use by W.H. Smith's new computerized system in 1967.

Assigned each book a fixed-length numeric code with publisher, edition, and check digits, replacing text with a reliable lookup that scaled to an international standard.

Titles and editions were verbose and inconsistent, causing errors in computer matching.

A fixed-length numeric code is compact and unambiguous, enabling fast, reliable lookups.

Structured digits for publisher and edition plus a check digit made the code scalable and error-resistant.

Industry-wide adoption created a standard that worked beyond one retailer, avoiding competing systems.

When free-text descriptions are too long or ambiguous for automated systems, replace them with a short, structured, unique code that machines can process instantly.

The SBN gave W.H. Smith's computer system a single, unambiguous number to store and match instead of comparing long, inconsistent text descriptions, and other retailers and publishers in the UK book trade adopted the same numbering scheme rather than build competing systems of their own.