Written by Christa Gatewood
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The International Standard Book (or Bibliographic) Number (ISBN) is a unique 10-digit number that identifies books in the commercial market. The system was set up to standardize information in the publishing industry and to ease book ordering. It was originally created in the UK in 1966. Back then it was call the SBN. When it became an internationally recognized number in 1970, it became known as the ISBN.

Understanding the ISBN system

Each ISBN consists of four parts to identify the book. The first numbers indicate the country of origin. All countries have been assigned a specific number to begin the ISBN. The next part of the number corresponds to the publisher. Publishers are assigned numbers by the national ISBN agency. The next numbers correspond to the item. Publishers are given ISBNs in blocks according to anticipated usage. The publishers then assign the item numbers as necessary. When they run out of ISBNs, they can receive another block of numbers with different publishers' numbers. Consequently, publishers may have more than one publisher number.

The final number in the ISBN is the check digit. This is determined by multiplying each preceding number by its place in the sequence of numbers. That number is then divided by 11 and the remainder is the check digit. Using a check digit in this way is done in order to detect errors in the number.

Different ISBNs are given to all printings of a book including hardcover and softcover editions of the same book. This prevents confusion when ordering from a retailer or wholesaler. ISBNs can typically be found on the title page of the book or on the back cover over the bar code.

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