A question about ISBN-10's - ending in X?

[Stephen]

I recently got a copy of The Thief Lord which has a 10 digit ISBN of 043942089x.

While I can find the book using the ISBN-13, the 10 digit search gives me an empty list. When I reviewed the thread about the improvements in the search facility that are currently being worked on, it sounds like ISBN's ending in x are considered "fakes"

Can someone explain a bit about how these things work or point me to a link that does?

[Emy]

043942089x isn't seen as an ISBN, but 043942089X is. The lower case and upper case register as separate characters :)

[Kara]

I'm a little confused. It's a check digit. It should not be considered a fake.

[Stephen]

Emy wrote: "043942089x isn't seen as an ISBN, but 043942089X is. The lower case and upper case register as separate characters :)"

Yes, ok. But should they? Particularly in a search where internet users are accustomed to pretty much everything being case-insensitive?

[Emy]

Stephen wrote: "Yes, ok. But should they? Particularly in a search where internet users are accustomed to pretty much everything being case-insensitive? "

Case sensitivity is something you would need to take to the Feedback forums, it's not something that GR Librarians can help with. Sorry :)

[Debbie's Spurts (D.A.)]

It's a bug reported in the feedback forum already. Fairly recent problem that cropped up.

They are actually working on the search feature for more than just that bug.

[Stephen]

Kara wrote: "I'm a little confused. It's a check digit. It should not be considered a fake."

This is the answer I was originally looking for. I'm familiar with the old mod-10 and mod-11 check digit generation algorithms but while I suspected X was a check digit of sorts, I'm unfamiliar with how one would be generated.

I've posted in the thread dealing with the new search changes now that I'm understanding ISBN's a bit better.
Thanx

[Emy]

Ah, yes, the last digit is always a check digit. Given that this is an issue that pops up in other contexts frequently, I suspect that ISBN checks only accept 0-9 and X as check digits, and that there is an added extra in the background that makes x and X recognisable. AFAIK isbn.org often fails searches on lowercase too.