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

Organisation  International ISBN Agency 
Introduced  1970; 49 years ago (1970) 
No. of digits  13 (formerly 10) 
Check digit  Weighted sum 
Example  9783161484100 
Website  isbninternational 
The International Standard Book Number (ISBN) is a numeric commercial book identifier which is intended to be unique.^{[a]}^{[b]} Publishers purchase ISBNs from an affiliate of the International ISBN Agency.^{[1]}
An ISBN is assigned to each separate edition and variation (except reprintings) of a publication. For example, an ebook, a paperback and a hardcover edition of the same book will each have a different ISBN. The ISBN is ten digits long if assigned before 2007, and thirteen digits long if assigned on or after 1 January 2007. The method of assigning an ISBN is nationspecific and varies between countries, often depending on how large the publishing industry is within a country.
The initial ISBN identification format was devised 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 9digit SBN code can be converted to a 10digit ISBN by prefixing it with a zero digit '0').
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 newspapers. The International Standard Music Number (ISMN) covers musical scores.
The Standard Book Numbering (SBN) code is a ninedigit 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 identification format was conceived in 1967 in the United Kingdom by David Whitaker^{[5]}^{[6]} (regarded as the "Father of the ISBN")^{[7]} and in 1968 in the United States by Emery Koltay^{[5]} (who later became director of the U.S. ISBN agency R.R. Bowker).^{[7]}^{[8]}^{[9]}
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 ninedigit 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.^{[10]}
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", where "340" indicates the publisher, "01381" is the serial number assigned by the publisher, and "8" is the check digit. By prefixing a zero, this can be converted to ISBN 0340013818; the check digit does not need to be recalculated.
Since 1 January 2007, ISBNs have contained thirteen digits, a format that is compatible with "Bookland" European Article Number EAN13s.^{[11]}
A separate ISBN is assigned to each edition and variation (except reprintings) of a publication. For example, an ebook, audiobook, paperback, and hardcover edition of the same book will each have a different ISBN assigned to it.^{[12]}^{:12} The ISBN is thirteen digits long if assigned on or after 1 January 2007, and ten digits long if assigned before 2007. An International Standard Book Number consists of four parts (if it is a 10digit ISBN) or five parts (for a 13digit ISBN).
Section 5 of the International ISBN Agency's official user manual^{[12]}^{:11} describes the structure of the 13digit ISBN, as follows:
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.^{[d]}
ISBN is most often used alongside other special identifiers to describe references in Wikipedia, and can help to find the same sources with different descriptions in various language versions (for example different spellings of the title or authors depending on the language).^{[14]}^{[15]}
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.^{[16]}
A full directory of ISBN agencies is available on the International ISBN Agency website.^{[17]} Partial listing:
The ISBN 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]}^{:11} and can be separated between hyphens, such as "9781...". Registration group identifiers have primarily been allocated within the 978 prefix element.^{[34]} The singledigit group identifiers within the 978prefix 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, 600–625, 65, 7, 80–94, 950–989, 9917–9989, and 99901–99983.^{[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.^{[37]} The registration group identifiers within prefix element 979 that have been assigned are 8 for the United States of America, 10 for France, 11 for the Republic of Korea, and 12 for Italy.^{[38]}
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.^{[39]} 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.^{[40]} 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. 
9386954214 
Englishspeaking area  Edupedia Publications Pvt Ltd. 
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:^{[41]}
Publication element length 
0 – Registration group element  1 – Registration group element  Total Registrants  

From  To  Registrants  From  To  Registrants  
6 digits  000xxxxxxx  019xxxxxxx  20  101xxxxxxx  106xxxxxxx  6  26 
5 digits  0200xxxxxx 0229xxxxxx 0370xxxxxx 0640xxxxxx 0649xxxxxx 0656xxxxxx 
0227xxxxxx 0368xxxxxx 0638xxxxxx 0647xxxxxx 0654xxxxxx 0699xxxxxx 
495  1000xxxxxx 1100xxxxxx 1714xxxxxx 
1009xxxxxx 1397xxxxxx 1716xxxxxx 
311  806 
4 digits  02280xxxxx 03690xxxxx 06390xxxxx 06550xxxxx 07000xxxxx 
02289xxxxx 03699xxxxx 06398xxxxx 06559xxxxx 08499xxxxx 
1,539  10700xxxxx 13980xxxxx 16860xxxxx 17170xxxxx 17900xxxxx 18672xxxxx 19730xxxxx 
10999xxxxx 15499xxxxx 17139xxxxx 17319xxxxx 17999xxxxx 18675xxxxx 19877xxxxx 
2,502  4,041 
3 digits  085000xxxx  089999xxxx  5,000  155000xxxx 174000xxxx 177540xxxx 177650xxxx 177770xxxx 180000xxxx 186760xxxx 
168599xxxx 177499xxxx 177639xxxx 177699xxxx 178999xxxx 186719xxxx 186979xxxx 
25,420  30,420 
2 digits  0900000xxx  0949999xxx  50,000  1869800xxx 1916506xxx 1987800xxx 
1915999xxx 1972999xxx 1998999xxx 
113,894  163,894 
1 digit  06399000xx 06480000xx 09500000xx 
06399999xx 06489999xx 09999999xx 
511,000  17320000xx 17750000xx 17764000xx 17770000xx 19160000xx 19990000xx 
17399999xx 17753999xx 17764999xx 17776999xx 19165059xx 19999999xx 
107,060  618,060 
Total  568,054  Total  249,193  817,247 
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 10digit ISBN is an extension of that for SBNs, so the two systems are compatible; an SBN prefixed with a zero (the 10digit ISBN) will give the same check digit as the SBN without the zero. The check digit is base eleven, and can be an integer between 0 and 9, or an 'X'. The system for 13digit ISBNs is not compatible with SBNs and will, in general, give a different check digit from the corresponding 10digit ISBN, so does not provide the same protection against transposition. This is because the 13digit code was required to be compatible with the EAN format, and hence could not contain an 'X'.
According to the 2001 edition of the International ISBN Agency's official user manual,^{[42]} the ISBN10 check digit (which is the last digit of the 10digit ISBN) must range from 0 to 10 (the symbol 'X' is used for 10), and must be such that the sum of the ten digits, each multiplied by its (integer) weight, descending from 10 to 1, is a multiple of 11. That is, if x_{i} is the ith digit numbered from right to left beginning at 1, then x_{1} must be chosen such that:
For example, for an ISBN10 of 0306406152:
Formally, using modular arithmetic, this is rendered:
It is also true for ISBN10s that the sum of all ten digits, each multiplied by its weight in ascending order from 1 to 10, is a multiple of 11. For this example:
Formally, this is rendered:
The two most common errors in handling an ISBN (e.g. when typing it or writing it down) are a single altered digit or the transposition of adjacent digits. It can be proven mathematically that all possible valid ISBN10s have at least two digits that are different from one another. It can also be proven that there are no pairs of valid ISBN10s with eight identical digits and two transposed digits. (These proofs are true only because the ISBN is less than eleven 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 were to occur in the publishing house and remain undetected, the book would be issued with an invalid ISBN.^{[43]}
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 10digit 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 (because 132 = 12×11) – 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. If the value of $x_{10}$ required to satisfy this condition is 10, then 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 result in a check digit value of 11−0 = 11, which is invalid. (Strictly speaking, the first "modulo 11" is not needed, 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.
Appendix 1 of the International ISBN Agency's official user manual^{[12]}^{:33} 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, this is rendered:
The calculation of an ISBN13 check digit begins with the first twelve digits of the 13digit 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 0–9 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).
An ISBN10 is converted to ISBN13 by prepending "978" to the ISBN10 and recalculating the final checksum digit using the ISBN13 algorithm. The reverse process can also be performed, but not for numbers commencing with a prefix other than 978, which have no 10digit equivalent.
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 called an EAN5 for the currency and the recommended retail price.^{[47]} For 10digit 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 alternating digits).
Partly because of an expected shortage in certain ISBN categories, the International Organization for Standardization (ISO) decided to migrate to a 13digit ISBN (ISBN13). The process began on 1 January 2005 and was planned to conclude on 1 January 2007.^{[48]} As of 2011^{[update]}, 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. The 10digit 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 thirteen 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 10digit ISBN check digit generally is not the same as the 13digit 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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