A 13digit ISBN, 9783161484100, as represented by an EAN13 bar code  
Acronym  ISBN 

Introduced  1970 
Managing organisation  International ISBN Agency 
No. of digits  13 (formerly 10) 
Check digit  Weighted sum 
Example  9783161484100 
Website 
www 
The International Standard Book Number (ISBN) is a unique^{[a]}^{[b]} numeric commercial book identifier. Publishers purchase ISBNs from an affiliate of the International ISBN Agency.^{[1]}
An ISBN is assigned to each edition and variation (except reprintings) of a book. For example, an ebook, a paperback and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, and 10 digits long if assigned before 2007. The method of assigning an ISBN is nationbased and varies from country to country, often depending on how large the publishing industry is within a country.
The initial ISBN configuration of recognition^{[clarification needed]} was generated in 1967 based upon the 9digit Standard Book Numbering (SBN) created in 1966. The 10digit ISBN format was developed by the International Organization for Standardization (ISO) and was published in 1970 as international standard ISO 2108 (the SBN code can be converted to a ten digit ISBN by prefixing it with a zero).
Privately published books sometimes appear without an ISBN. The International ISBN agency sometimes assigns such books ISBNs on its own initiative.^{[2]}
Another identifier, the International Standard Serial Number (ISSN), identifies periodical publications such as magazines; and the International Standard Music Number (ISMN) covers for musical scores.
The Standard Book Numbering (SBN) code is a 9digit commercial book identifier system created by Gordon Foster, Emeritus Professor of Statistics at Trinity College, Dublin,^{[3]} for the booksellers and stationers WHSmith and others in 1965.^{[4]} The ISBN configuration of recognition was generated in 1967 in the United Kingdom by David Whitaker^{[5]} (regarded as the "Father of the ISBN"^{[6]}) and in 1968 in the United States by Emery Koltay^{[5]} (who later became director of the U.S. ISBN agency R.R. Bowker).^{[6]}^{[7]}^{[8]}
The 10digit ISBN format was developed by the International Organization for Standardization (ISO) and was published in 1970 as international standard ISO 2108.^{[4]}^{[5]} The United Kingdom continued to use the 9digit SBN code until 1974. ISO has appointed the International ISBN Agency as the registration authority for ISBN worldwide and the ISBN Standard is developed under the control of ISO Technical Committee 46/Subcommittee 9 TC 46/SC 9. The ISO online facility only refers back to 1978.^{[9]}
An SBN may be converted to an ISBN by prefixing the digit "0". For example, the second edition of Mr. J. G. Reeder Returns, published by Hodder in 1965, has "SBN 340 01381 8" – 340 indicating the publisher, 01381 their serial number, and 8 being the check digit. This can be converted to ISBN 0340013818; the check digit does not need to be recalculated.
Since 1 January 2007, ISBNs have contained 13 digits, a format that is compatible with "Bookland" European Article Number EAN13s.^{[10]}
An ISBN is assigned to each edition and variation (except reprintings) of a book. For example, an ebook, a paperback, and a hardcover edition of the same book would each have a different ISBN.^{[11]} The ISBN is 13 digits long if assigned on or after 1 January 2007, and 10 digits long if assigned before 2007. An International Standard Book Number consists of 4 parts (if it is a 10 digit ISBN) or 5 parts (for a 13 digit ISBN):
A 13digit ISBN can be separated into its parts (prefix element, registration group, registrant, publication and check digit), and when this is done it is customary to separate the parts with hyphens or spaces. Separating the parts (registration group, registrant, publication and check digit) of a 10digit ISBN is also done with either hyphens or spaces. Figuring out how to correctly separate a given ISBN is complicated, because most of the parts do not use a fixed number of digits.^{[14]}
ISBN issuance is countryspecific, in that ISBNs are issued by the ISBN registration agency that is responsible for that country or territory regardless of the publication language. The ranges of ISBNs assigned to any particular country are based on the publishing profile of the country concerned, and so the ranges will vary depending on the number of books and the number, type, and size of publishers that are active. Some ISBN registration agencies are based in national libraries or within ministries of culture and thus may receive direct funding from government to support their services. In other cases, the ISBN registration service is provided by organisations such as bibliographic data providers that are not government funded.^{[15]}
A full directory of ISBN agencies is available on the International ISBN Agency website.^{[16]} Partial listing:
The registration group identifier is a 1 to 5digit number that is valid within a single prefix element (i.e. one of 978 or 979).^{[12]} Registration group identifiers have primarily been allocated within the 978 prefix element.^{[34]} The singledigit group identifiers within the 978 prefix element are: 0 or 1 for Englishspeaking countries; 2 for Frenchspeaking countries; 3 for Germanspeaking countries; 4 for Japan; 5 for Russianspeaking countries; and 7 for People's Republic of China. An example 5digit group identifier is 99936, for Bhutan. The allocated group IDs are: 0–5, 600–621, 7, 80–94, 950–989, 9926–9989, and 99901–99976.^{[35]} Books published in rare languages typically have longer group identifiers.^{[36]}
Within the 979 prefix element, the registration group identifier 0 is reserved for compatibility with International Standard Music Numbers (ISMNs), but such material is not actually assigned an ISBN.^{[12]} The registration group identifiers within prefix element 979 that have been assigned are 10 for France, 11 for the Republic of Korea, and 12 for Italy.^{[37]}
The original 9digit standard book number (SBN) had no registration group identifier, but prefixing a zero (0) to a 9digit SBN creates a valid 10digit ISBN.
The national ISBN agency assigns the registrant element (cf. Category:ISBN agencies) and an accompanying series of ISBNs within that registrant element to the publisher; the publisher then allocates one of the ISBNs to each of its books. In most countries, a book publisher is not required by law to assign an ISBN; however, most bookstores only handle ISBN bearing publications.^{[citation needed]}
A listing of more than 900,000 assigned publisher codes is published, and can be ordered in book form (€1399, US$1959). The web site of the ISBN agency does not offer any free method of looking up publisher codes.^{[38]} Partial lists have been compiled (from library catalogs) for the Englishlanguage groups: identifier 0 and identifier 1.
Publishers receive blocks of ISBNs, with larger blocks allotted to publishers expecting to need them; a small publisher may receive ISBNs of one or more digits for the registration group identifier, several digits for the registrant, and a single digit for the publication element. Once that block of ISBNs is used, the publisher may receive another block of ISBNs, with a different registrant element. Consequently, a publisher may have different allotted registrant elements. There also may be more than one registration group identifier used in a country. This might occur once all the registrant elements from a particular registration group have been allocated to publishers.
By using variable block lengths, registration agencies are able to customise the allocations of ISBNs that they make to publishers. For example, a large publisher may be given a block of ISBNs where fewer digits are allocated for the registrant element and many digits are allocated for the publication element; likewise, countries publishing many titles have few allocated digits for the registration group identifier and many for the registrant and publication elements.^{[39]} Here are some sample ISBN10 codes, illustrating block length variations.
ISBN  Country or area  Publisher 

9992158107  Qatar  NCCAH, Doha 
9971502100  Singapore  World Scientific 
9604250590  Greece  Sigma Publications 
8090273416  Czech Republic; Slovakia  Taita Publishers 
8535902775  Brazil  Companhia das Letras 
1843560283  Englishspeaking area  Simon Wallenberg Press 
0684843285  Englishspeaking area  Scribner 
080442957X  Englishspeaking area  Frederick Ungar 
0851310419  Englishspeaking area  J. A. Allen & Co. 
0943396042  Englishspeaking area  Willmann–Bell 
097522980X  Englishspeaking area  KT Publishing 
Englishlanguage registration group elements are 0 and 1 (2 of more than 220 registration group elements). These two registration group elements are divided into registrant elements in a systematic pattern, which allows their length to be determined, as follows:^{[40]}
Publication element length 
0 – Registration group element  1 – Registration group element  Total Registrants  

From  To  Registrants  From  To  Registrants  
6 digits  000xxxxxxx  019xxxxxxx  20  100xxxxxxx  109xxxxxxx  10  30 
5 digits  0200xxxxxx  0699xxxxxx  500  1100xxxxxx  1399xxxxxx  300  800 
4 digits  07000xxxxx  08499xxxxx  1,500  14000xxxxx  15499xxxxx  1,500  3,000 
3 digits  085000xxxx  089999xxxx  5,000  155000xxxx  186979xxxx  31,980  36,980 
2 digits  0900000xxx  0949999xxx  50,000  1869800xxx  1998999xxx  129,200  179,200 
1 digit  09500000xx  09999999xx  500,000  19990000xx  19999999xx  10,000  510,000 
Total  557,020  Total  172,990  730,010 
A check digit is a form of redundancy check used for error detection, the decimal equivalent of a binary check bit. It consists of a single digit computed from the other digits in the number. The method for the ten digit code is an extension of that for SBNs, the two systems are compatible, and SBN prefixed with "0" will give the same checkdigit as without – the digit is base eleven, and can be 09 or X. The system for thirteen digit codes is not compatible and will, in general, give a different check digit from the corresponding 10 digit ISBN, and does not provide the same protection against transposition. This is because the thirteen digit code was required to be compatible with the EAN format, and hence could not contain an "X".
The 2001 edition of the official manual of the International ISBN Agency says that the ISBN10 check digit^{[41]} – which is the last digit of the tendigit ISBN – must range from 0 to 10 (the symbol X is used for 10), and must be such that the sum of all the ten digits, each multiplied by its (integer) weight, descending from 10 to 1, is a multiple of 11.
For example, for an ISBN10 of 0306406152:
Formally, using modular arithmetic, we can say:
It is also true for ISBN10's that the sum of all the ten digits, each multiplied by its weight in ascending order from 1 to 10, is a multiple of 11. For this example:
Formally, we can say:
The two most common errors in handling an ISBN (e.g., typing or writing it) are a single altered digit or the transposition of adjacent digits. It can be proved that all possible valid ISBN10's have at least two digits different from each other. It can also be proved that there are no pairs of valid ISBN10's with eight identical digits and two transposed digits. (These are true only because the ISBN is less than 11 digits long, and because 11 is a prime number.) The ISBN check digit method therefore ensures that it will always be possible to detect these two most common types of error, i.e. if either of these types of error has occurred, the result will never be a valid ISBN – the sum of the digits multiplied by their weights will never be a multiple of 11. However, if the error occurs in the publishing house and goes undetected, the book will be issued with an invalid ISBN.^{[42]}
In contrast, it is possible for other types of error, such as two altered nontransposed digits, or three altered digits, to result in a valid ISBN (although it is still unlikely).
Each of the first nine digits of the tendigit ISBN—excluding the check digit itself—is multiplied by its (integer) weight, descending from 10 to 2, and the sum of these nine products found. The value of the check digit is simply the one number between 0 and 10 which, when added to this sum, means the total is a multiple of 11.
For example, the check digit for an ISBN10 of 030640615? is calculated as follows:
Adding 2 to 130 gives a multiple of 11 (132 = 12 x 11) − this is the only number between 0 and 10 which does so. Therefore, the check digit has to be 2, and the complete sequence is ISBN 0306406152. The value required to satisfy this condition might be 10; if so, an 'X' should be used.
Alternatively, modular arithmetic is convenient for calculating the check digit using modulus 11. The remainder of this sum when it is divided by 11 (i.e. its value modulo 11), is computed. This remainder plus the check digit must equal either 0 or 11. Therefore, the check digit is (11 minus the remainder of the sum of the products modulo 11) modulo 11. Taking the remainder modulo 11 a second time accounts for the possibility that the first remainder is 0. Without the second modulo operation the calculation could end up with 11 – 0 = 11 which is invalid. (Strictly speaking the first "modulo 11" is unneeded, but it may be considered to simplify the calculation.)
For example, the check digit for the ISBN10 of 030640615? is calculated as follows:
Thus the check digit is 2.
It is possible to avoid the multiplications in a software implementation by using two accumulators. Repeatedly adding t
into s
computes the necessary multiples:
// Returns ISBN error syndrome, zero for a valid ISBN, nonzero for an invalid one.
// digits[i] must be between 0 and 10.
int CheckISBN(int const digits[10])
{
int i, s = 0, t = 0;
for (i = 0; i < 10; i++) {
t += digits[i];
s += t;
}
return s % 11;
}
The modular reduction can be done once at the end, as shown above (in which case s
could hold a value as large as 496, for the invalid ISBN 999999999X), or s
and t
could be reduced by a conditional subtract after each addition.
The 2005 edition of the International ISBN Agency's official manual^{[43]} describes how the 13digit ISBN check digit is calculated. The ISBN13 check digit, which is the last digit of the ISBN, must range from 0 to 9 and must be such that the sum of all the thirteen digits, each multiplied by its (integer) weight, alternating between 1 and 3, is a multiple of 10.
Formally, using modular arithmetic, we can say:
The calculation of an ISBN13 check digit begins with the first 12 digits of the thirteendigit ISBN (thus excluding the check digit itself). Each digit, from left to right, is alternately multiplied by 1 or 3, then those products are summed modulo 10 to give a value ranging from 0 to 9. Subtracted from 10, that leaves a result from 1 to 10. A zero (0) replaces a ten (10), so, in all cases, a single check digit results.
For example, the ISBN13 check digit of 978030640615? is calculated as follows:
s = 9×1 + 7×3 + 8×1 + 0×3 + 3×1 + 0×3 + 6×1 + 4×3 + 0×1 + 6×3 + 1×1 + 5×3 = 9 + 21 + 8 + 0 + 3 + 0 + 6 + 12 + 0 + 18 + 1 + 15 = 93 93 / 10 = 9 remainder 3 10 – 3 = 7
Thus, the check digit is 7, and the complete sequence is ISBN 9780306406157.
In general, the ISBN13 check digit is calculated as follows.
Let
Then
This check system – similar to the UPC check digit formula – does not catch all errors of adjacent digit transposition. Specifically, if the difference between two adjacent digits is 5, the check digit will not catch their transposition. For instance, the above example allows this situation with the 6 followed by a 1. The correct order contributes 3×6+1×1 = 19 to the sum; while, if the digits are transposed (1 followed by a 6), the contribution of those two digits will be 3×1+1×6 = 9. However, 19 and 9 are congruent modulo 10, and so produce the same, final result: both ISBNs will have a check digit of 7. The ISBN10 formula uses the prime modulus 11 which avoids this blind spot, but requires more than the digits 09 to express the check digit.
Additionally, if the sum of the 2nd, 4th, 6th, 8th, 10th, and 12th digits is tripled then added to the remaining digits (1st, 3rd, 5th, 7th, 9th, 11th, and 13th), the total will always be divisible by 10 (i.e., end in 0).
The conversion is quite simple as one only needs to prefix "978" to the existing number and calculate the new checksum using the ISBN13 algorithm.
Publishers and libraries have varied policies about the use of the ISBN check digit. Publishers sometimes fail to check the correspondence of a book title and its ISBN before publishing it; that failure causes book identification problems for libraries, booksellers, and readers.^{[44]} For example, ISBN 0590764845 is shared by two books – Ninja gaiden®: a novel based on the bestselling game by Tecmo (1990) and Wacky laws (1997), both published by Scholastic.
Most libraries and booksellers display the book record for an invalid ISBN issued by the publisher. The Library of Congress catalogue contains books published with invalid ISBNs, which it usually tags with the phrase "Cancelled ISBN".^{[45]} However, bookordering systems such as Amazon.com will not search for a book if an invalid ISBN is entered to its search engine.^{[citation needed]} OCLC often indexes by invalid ISBNs, if the book is indexed in that way by a member library.
Only the term "ISBN" should be used; the terms "eISBN" and "eISBN" have historically been sources of confusion and should be avoided. If a book exists in one or more digital (ebook) formats, each of those formats must have its own ISBN. In other words, each of the three separate EPUB, Amazon Kindle, and PDF formats of a particular book will have its own specific ISBN. They should not share the ISBN of the paper version, and there is no generic "eISBN" which encompasses all the ebook formats for a title.^{[46]}
Currently the barcodes on a book's back cover (or inside a massmarket paperback book's front cover) are EAN13; they may have a separate barcode encoding five digits for the currency and the recommended retail price.^{[47]} For 10 digit ISBNs, the number "978", the Bookland "country code", is prefixed 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 an expected shortage in certain ISBN categories, the International Organization for Standardization (ISO) decided to migrate to a thirteendigit ISBN (ISBN13). The process began 1 January 2005 and was planned to conclude 1 January 2007.^{[48]} As of 2011, all the 13digit ISBNs began with 978. As the 978 ISBN supply is exhausted, the 979 prefix was introduced. Part of the 979 prefix is reserved for use with the Musicland code for musical scores with an ISMN. 10 digit ISMN codes differed visually as they began with an "M" letter; the bar code represents the "M" as a zero (0), and for checksum purposes it counted as a 3. All ISMNs are now 13 digits commencing 9790; 9791 to 9799 will be used by ISBN.
Publisher identification code numbers are unlikely to be the same in the 978 and 979 ISBNs, likewise, there is no guarantee that language area code numbers will be the same. Moreover, the tendigit ISBN check digit generally is not the same as the thirteendigit ISBN check digit. Because the GTIN13 is part of the Global Trade Item Number (GTIN) system (that includes the GTIN14, the GTIN12, and the GTIN8), the 13digit ISBN falls within the 14digit data field range.^{[49]}
Barcode format compatibility is maintained, because (aside from the group breaks) the ISBN13 barcode format is identical to the EAN barcode format of existing 10digit ISBNs. So, migration to an EANbased system allows booksellers the use of a single numbering system for both books and nonbook products that is compatible with existing ISBN based data, with only minimal changes to information technology systems. Hence, many booksellers (e.g., Barnes & Noble) migrated to EAN barcodes as early as March 2005. Although many American and Canadian booksellers were able to read EAN13 barcodes before 2005, most general retailers could not read them. The upgrading of the UPC barcode system to full EAN13, in 2005, eased migration to the ISBN13 in North America.
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