Quote:
Originally Posted by Robbeli
The actual number is even smaller. The first three digits indicate that it is a book. They are always 978 (can also be 979 in the future). The last digit is a checksum digit, so it leaves only 2*10^8 possible numbers. Considering that the ISBN includes a country code and a publisher code, so you cannot use every number, it probably leaves only 2*10^7 usable ISBN's. Twenty million books is not that much.
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It is actually much smaller than that. Only three digits are used to identify the book itself, so that gives the same publisher only 1,000 ISBNs for each country code (unless the publisher has more than one publisher code).
After thinking about it, a more workable solution to the problem it could be a universal book ID number (one completely separate from the ISBN) to identify a specific book. When a book is first released it gets an ID number, and all future versions of that book carry the same ID number.
To provide an illustration, the code could be as follows (each part is separated by a period):
- Language Number: A three digit code that indicates the book's language.
- ID Number: A nine digit code (allows for 1,000,000,000 titles) that identifies a specific book.
- Abridgement Number: A one digit code that indicates if the book is/is not an abridgement of the original book (not uncommon with audiobooks).
- Version Code: A three digit number to the specific format (printed hardback, printed paperback, PDF edition, and so on).
Just a thought. What do you think?