Get Ready for ISBN-13 and 979
We're rapidly approaching January 1, 2007, when two important developments in the history of ISBN occur.
First, the 10-digit ISBN (known now as ISBN-10) will no longer be the standard for use. R.R. Bowker, which coordinates ISBNs in the US, says that ISBN-10s can be phased out from use on books starting on January 1. It's not obligatory to get rid of them, but it will make less and less sense, because of point 2.
Second, the use of ISBN-13s that start with 979 will come into being. Up until Dec. 31, 2006, ISBN-10s have been freely convertible into EAN UPCs, or the global barcodes used to identify national origin and product stockkeeping unit (SKU) numbers. ISBN-10 can be converted by taking the digits 978 plus the first nine digits of the ISBN-10 and computing a new base-10 checksum for digit 13. (ISBNs use base 11, where the 10th digit can be zero through nine, or X representing 10 in base 11.)
With the introduction of 979s, not all ISBN-13s will be convertible into ISBN-10s; only 978-prepended ISBN-13s have a corresponding ISBN-10.
The reason for this is numberspace. They've run out of ISBNs in the current 10-digit space, and by adding another EAN prefix, they buy 10 to the 9th power potential new ISBNs. These are assigned in blocks to publishers, based on the publisher's scale and country of operation, and thus the numbers are used inefficiently. Certain ranges are reserved, as well.
I wrote about this at some length and less clarity two years ago. The deadline is finally upon us!