International Standard Book Number the Unique Book Identifier

The International Standard Book Number (ISBN) is a unique, numerical commercial book identifier. It is a unique machine-readable identification number, which marks any book unmistakably and has revolutionised the international book-trade. In 1966 the book sellers and stationers created the 9 digit Standard Book Number (SBN) in UK. In order to standardise the code, the 10-digit International Standard Book Number (ISBN) format was developed by the International Organization for Standardization. This number is defined in ISO Standard 2108 in 1970. (however, SBN code continued in the UK till 1974). The ISO TC 46/SC 9, is solely responsible for the standard. Since 1 January 2007, ISBN are of 13 digits, compatible with Bookland EAN-13s. The ISBN has been in use now for 38 years and 170 countries and territories are officially ISBN members. The ISBN accompanies a publication from its production onwards.

An ISBN consists of 5 parts of variable length and the parts must be separated

clearly by hyphens or spaces:

ISBN  978-0-571-08988-8 or  ISBN  978 0 571 08988 8

The five groups for a 13 digit ISBN include:

1. global standards (GS1) prefix: 978 or 979
2. the group identifier, the group identifier is a 1 to 5 digit number. (language-sharing country group)

0        English ) (UK, US, Australia, NZ, Canada,

1        English )  South Africa, Zimbabwe)

2        French    

3        German    

81       India (see also 93)

92       International (Unesco and EEC)

93       India (see also 81)

1. the publisher code, The national ISBN agency assigns the publisher code. In India ISBN system was put into operation in January 1985 as Raja Rammohun Roy National Agency for ISBN, India, by the Ministry of Human Resource Development, Department of Secondary & Higher Education, New Delhi.
2. the item number, and
3. a checksum character or check digit.

The number of digits in the second, third and fourth parts of the ISBN (group identifier, publisher prefix, title identifier) varies. The number of digits in the group number and in the publisher prefix is determined by the quantity of titles planned to be produced by the publisher or publisher group. Publishers or publisher groups with large title outputs are represented by fewer digits.

The calculation of an ISBN-13 check digit begins with the first 12 digits of the thirteen-digit 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 ISBN-13 check digit of  978-0-571-08988-?  is calculated as follows:

ISBN  978 0 571 08988 8

s = 9×1 + 7×3 + 8×1 + 0×3 + 5×1 + 7×3 + 1×1 + 0×3 + 8×1 + 9×3 + 8×1 + 8×3
  =   9 +  21 +   8 +   0 +   5 +   21 +   1 +  0 +   8 +  27 +   8 +  27
  = 135
135 / 10 = 13 remainder 5
13 – 5 
= 8 

Thus, the check digit is 8, and the complete sequence is ISBN  978 0 571 08988 8

Reference: http://www.isbn-international.org/en