ISBNs are about to become 13 digits long, 3 more than their current 10. I have been thinking about the best way to handle the transition on the Book Gallery website and so decided to share a few ISBN facts with you.

1) ISBN stands for International Standard Book Number. It was formed in Britain in 1966 by the W H Smith booksellers. It was adopted internationally in 1970, under ISO 2108.

2) The 10-digit is actually 9 digits long, and includes a test number. How a computer double checks the validity of the ISBN is it takes 10 times the first number, 9 times the second number, 8 times the third, etc etc, and then adds the last digit. The last digit is the only one that can be larger than 9 (it can be X, or equal to 10). The total sum should be a multiple of 11. (I have heard that ISBNs also work in reverse, multiplying the first digit by 1, the second by 2, etc and then adding the 10th digit, again checking modulo 11. I am too lazy to check this at present.).

3) The ISBN is not a random series of numbers, nor is it only a sequential numbering of books. It continues a brief country/language code (english seems to be 1 or 0), a several digit publisher code (3 digits for English language publishers, I believe), and a several digit book item number (5, or the remainder). As far as I know, there is no system that dictates what item number a book publisher assigns, though most probably are fairly sequential to save headaches. I do not know if publishers are assigned a number or choose numbers, though I suppose it is the former.

4) The new 13 digit ISBN is actually just bringing it up to EAN standards. Books currently have a GS1 of 978 (look at their barcode, the first three digits should be most likely be 978, currently) but will be expanded to 978 and 979 starting January of next year. This means that some publishers will be new codes, though some will probably retain their old numbers. Pretty much assume all old numbers will be obsolete, though, for safety sake.

(bonus fact, ever wonder why a barcode seems to have the ISBN in it, but the last digit is sometimes wrong and the first three digits are different? Well, I've told you the latter, and now will explain the former)

5) The new system, though, is only going to involve a modulo 10 system. The first digit is to be muliplied by 1, the second by 3, the third by 1, the fourth by 3, etc etc. This means that the last digit should be added to make the whole thing a multiple of 10. Note: this is the number already used on barcodes for books. Since the check digit is different, this means that even if a company retains its publisher code and its product code, it cannot simply add the 979 to it, it must also derive the check digit, effectively altering the code.

Written by W Doug Bolden

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