ISBN

The International Standard Book Number, or ISBN (sometimes pronounced [ˈɪzbən]), is a unique identifier for books, intended to be used commercially. The ISBN system was created in the United Kingdom in 1966 by the booksellers and stationers W H Smith and originally called Standard Book Numbering or SBN (still used in 1974). It was adopted as international standard ISO 2108 in 1970. A similar identifier, the International Standard Serial Number (ISSN), is used for periodical publications such as magazines. From January 1 2007, ISBNs will be 13 digits long.

Overview

Each edition and variation (except reprints) of a book receives its own ISBN. The number is either 10 or 13 digits long (from 1 January 2007), and consists of four or five parts:

1. if 13-digit ISBN, a GS1 Prefix, either 978 or 979
2. the country of origin or language code,
3. the publisher,
4. the item number, and
5. a checksum character or check digit.

The different parts can have different lengths and are usually separated by hyphens or spaces - the international ISBN agency "ISBN User Manual" states "The ten-digit number is divided into four parts of variable length, which must be separated clearly by hyphens or spaces" although it allows these to be omitted for internal data processing as the prefix code ensures that no two codes start the same way. If present, hyphens must be placed correctly; however they are not always practically sufficient for identifying the publisher since the listing of all assigned publisher identifiers The Publishers International ISBN Directory (PIID) is a chargeable periodical publication.

The country field is 0 for English speaking countries, 2 for French speaking countries, 3 for German speaking countries, 4 for Japanese, 5 for Russian, etc. (The original SBN lacked the country field, but prefixing 0 to a 9-digit SBN creates a valid ISBN.) The country field can be up to 5 digits long; 99936 for instance is used for Bhutan.

The publisher number is assigned by the national ISBN agency, and the item number is chosen by the publisher. There is, in general, no requirement for a publisher to assign an ISBN to a book nor for that book to display its number — but see below for the exception in China. However, many bookstores will only deal with items bearing an ISBN.

Publishers receive blocks of ISBNs, with larger blocks going to publishers that are expected to need them; a small publisher might receive ISBNs consisting of a digit for the language, seven digits for the publisher, and a single digit for the individual items. Once that block is used up, the publisher can receive another block of numbers, with a different publisher number. As a consequence, different publisher numbers may correspond to the same publisher.

Check digit

The International ISBN Agency in its official manual states that the 10-digit ISBN check digit, which is the last digit of the 10 digit ISBN, is calculated on a modulus 11 with weights 10 to 2, using X instead of 10 where ten would occur as a check digit. This means that each of the first nine digits of the 10-digit ISBN—excluding the check digit itself—is multiplied by a number in a sequence from 10 to 2 and that the resulting sum of the products, plus the check digit, must be divisible by 11 without a remainder.

By this method the calculation for the 10-digit ISBN whose first nine digits are 0-306-40615 would be done thus:

  10×0 + 9×3 + 8×0 + 7×6 + 6×4 + 5×0 + 4×6 + 3×1 + 2×5
=  0  +  27  +  0  +  42 +  24 +  0  +  24 +  3  +  10
= 130
The next complete multiple of 11 is 12×11 = 132
132 - 130 = 2

So the check digit is 2, and the complete sequence is ISBN 0-306-40615-2.

A second method to find the check digit is by first multiplying each digit of the 10-digit ISBN by that digit's place in the number sequence from 1 to 9, with the leftmost digit being multiplied by 1, the next digit by 2, and so on. Next, take the sum of these multiplications and calculate the sum modulo 11, with "10" represented by the character "X". For example, to find the check digit for the 10-digit ISBN whose first nine digits are 0-306-40615:

  1×0 + 2×3 + 3×0 + 4×6 + 5×4 + 6×0 + 7×6 + 8×1 + 9×5
=  0  +  6  +  0  +  24 +  20 +  0  +  42 +  8  +  45
= 145
= 13×11 + 2

So the check digit is 2, and the complete sequence is ISBN 0-306-40615-2.

For those more mathematically inclined, it should be noticed that a 10-digit ISBN's check digit is "actually" computed via dot products. (1,2,3,4,5,6,7,8,9) dot (x,x,x,x,x,x,x,x,x) mod 11 = check digit.

The two most common errors which occur when handling an ISBN (e.g., typing it in or writing it down) are an altered digit or transposition of adjacent digits. Since 11 is a prime number, the ISBN check digit method ensures that these two kinds of errors will always be detected. If the error occurs at the publisher, and is not detected, the book can be issued with a theoretically invalid ISBN.

EAN format used in barcodes, and planned upgrade

Currently, the barcodes found on the backs of books (or inside front covers of mass-market paperbacks) are EAN-13; they may be "Bookland"—that is, with a separate barcode encoding five digits for the currency and recommended retail price. "978", the asset code for books, is prepended to the ISBN in the barcode data, and the check digit is recalculated according to the EAN13 formula (modulo 10, 1x, and 3x weighting on alternate digits).

Partly because of a pending shortage in certain ISBN categories, the International Organization for Standardization (ISO) started migrating to a thirteen-digit ISBN (sometimes referred to as ISBN-13) in a process that began on 1 January 2005 and will finish on 1 January 2007. There is a FAQ document about this change. Existing ISBNs will be prefixed with "978" (and the check digit recalculated); as the "978" ISBNs are exhausted, the "979" prefix will be introduced. This is expected to happen more rapidly outside the US. ("979" was originally the "Musicland" code for musical scores bearing an ISMN, howver ISMN codes will be different in that visually they start with an M, and while the bar code will represent the M as a 0, for checksum purposes it will count as a 3.) Note that publisher identification codes are unlikely to be the same in 978 and 979 ISBNs. Moreover, the old ISBN check digit for a book (when they were 10 digits long) is generally not going to be the same as the book's new check digit in its 13-digit ISBN.

Since the new 13-digit ISBNs will be identical to the EAN barcoded format of any existing 10-digit ISBNs, this process will not break compatibility with any existing barcodes. This means that moving to an EAN-based system will allow booksellers to use a single numbering system for both book and non-book products without breaking backwards compatibility with existing ISBN-based information, and with only minimal changes to their information technology (IT) systems. For this reason, many booksellers, including Barnes & Noble, have started the process of phasing out usage of ISBNs in favour of using EAN codes as early as March 2005. Although many booksellers in the U.S. and Canada have been able to read EAN-13 barcodes for many years, most general retailers could not prior to 2005. The upgrading of the UPC barcode system to full EAN-13 in 2005 makes the transition to ISBN-13 all the easier in North America.

There is one retrograde aspect of the adoption of the EAN barcode system for books: it is less capable of detecting errors by comparison to the old ISBN system (before January 1 2007). The EAN barcode uses modulus 10, which is not a prime, and while the system of weights (alternating 1 and 3) lets EAN detect any single digit error, not all adjacent transposition errors can be detected (one in nine cannot). This is the best that can be achieved with a single decimal check digit.

ISBNs and book censorship in the People's Republic of China

ISBNs are used as a means of book censorship in the People's Republic of China. For a printer to legally print a run of books, they must have an ISBN, which are assigned in blocks to state owned publishing houses. However, since the 1990s, this means of censorship has become much less effective as state publishing houses, which have been weaned from government subsidy like all state owned enterprises, will now sell ISBNs to the highest bidder without regard to the content.

See also

• ASIN (Amazon Standard Identification Number)
• CODEN
• ESBN (Electronic Standard Book Number, see also http://esbn.org )
• ISEN (Internet Search Environment Number, see http://isen.org)
• ISAN (International Standard Audiovisual Number)
• ISSN (International Standard Serial Number)
• ISWC (International Standard Work Code, see http://iswc.org )
• Library of Congress Control Number
• Wikipedia:ISBN, use of ISBN on Wikipedia

External links

• ISO 2108:2005 at www.iso.org
• Brief Summary of ISBN
• How to find a book from Wikibooks
• ISBN to EAN EAS EBS CONELRAD transition at isbn.org
• Description of the ISBN to EAN upgrade process at bookweb.org
• How to Create an ISBN Barcode for a Book Tutorial

National and international agencies

• International ISBN Agency—coordinates and supervises the world-wide use of the ISBN system.
• ISBN Agency Australia—Thorpe-Bowker, a division of R R Bowker LLC
• ISBN agency for UK and Republic of Ireland—Nielsen BookData
• ISBN agency for US and Puerto Rico—R.R. Bowker LLC
• Numerical List of Group Identifiers List of language/region prefixes

Online tools

• Free 10-digit to 13-digit conversion tool
• The ISBN tools website has open-source Java classes to implement 10- and 13-digit ISBNs.
• Publisher access system for Books In Print and Global Books In Print database products
• Kimba Kano—Internet Explorer and Firefox add-on adding built-in ISBN & ASIN searching.
• ISBN check form checks checksum of an ISBN-10; outputs list of possible correct ISBN when the input is incorrect.
• ISBNdb.com—find books by ISBN, author, title, subject, et cetera; auto-corrects ISBN checksums if needed.
• ISBN.nu—offers free searching of a titles database.
• Yet another ISBN lookup tool that searches a number of database and bookseller sites.
• RFC 3187 Using International Standard Book Numbers as Uniform resource names (URN)
• Online tool to produce barcodes from ISBNs.
• ISBN-13 For Dummies
• Implementation guidelines (pdf document) for the 13 digit ISBN code.
• ISBN-10 To ISBN-13 Web Service ISBN-10 To ISBN-13 Web Service and Online Tools.
• ISBN Encoding Learn how it works, see how it converts to a barcode