## [bksvol-discuss] everything you want to know about ISBN numbers and more

• From: Cindy <popularplace@xxxxxxxxx>
• To: bksvol-discuss@xxxxxxxxxxxxx
• Date: Thu, 31 Aug 2006 00:33:31 -0700 (PDT)

I googled and found the following:

http://www.isbn.org/standards/home/isbn/us/isbnqa.asp#Q5
Why do some ISBNs end in an "X"?
In the case of the check digit, the last digit of
the ISBN, the upper case X can appear. The method of
determining the check digit for the ISBN is the
modulus 11 with the weighting factors 10 to 1. The
Roman numeral X is used in lieu of 10 where ten would
occur as a check digit."

WWhat you may ask, is a check digit. (At least I
wanted to know.) I found a simple definition after a
while: The source below not only explains what a check
digit is, but discusses several different kinds
besides ISBN check digits.

http://www.augustana.ab.ca/~mohrj/algorithms/checkdigit.html
"Check Digit
A decimal (or alphanumeric) digit added to a
number for the purpose of detecting the sorts of
errors humans typically make on data entry.

When human beings use numbers - whether keying them
into computers, dialing them on telephones, or reading
them and telling them to others --- they tend to make
certain kinds of mistakes more often than others.
According to Richard Hamming (Coding and Information
Theory, 2e, Prentice-Hall, 1986, p. 27), the two most
common human errors are:

* Interchanging adjacent digits of numbers:
67 becomes 76
* Doubling the wrong one of a triple of digits,
two adjacent ones of which are the same:
667 becomes 677"

A couple of sources explain how the ISBN  check digit
is arrived at. Jake and probably other mathematicians
would possibly understand it--it seems to have to do
with adding the digits in the ISBN number and dividing
by 11. Here's a URL if you want to read more about it.
(I'm more into words than numbers--I gave up quickly
on trying to solve even the easiest Siduko so I wona't
give the explanation here. You can look it up
yourself.) smile)

or a fuller explanation of why and what the parts of
an ISBN number stand for, read this:

http://www.isbn.org/standards/home/isbn/us/isbnqa.asp
What is an ISBN?
The International Standard Book Number (ISBN) is a
10-digit number that uniquely identifies books and
book-like products published internationally.

What is the purpose of an ISBN?
The purpose of the ISBN is to establish and
identify one title or edition of a title from one
specific publisher and is unique to that edition,
allowing for more efficient marketing of products by
booksellers, libraries, universities, wholesalers and
distributors.

What is the format of the ISBN?
Every ISBN consists of ten digits and whenever it
is printed it is preceded by the letters ISBN. The
ten-digit number is divided into four parts of
variable length, each part separated by a hyphen.

Does the ISBN have any meaning imbedded in the
numbers?
The four parts of an ISBN are as follows:
Group or country identifier which identifies a
national or geographic grouping of publishers;
Publisher identifier which identifies a particular
publisher within a group;
Title identifier which identifies a particular
title or edition of a title;
Check digit is the single digit at the end of the
ISBN which validates the ISBN."

"Does the ISBN have any meaning imbedded in the
numbers?
The four parts of an ISBN are as follows:
Group or country identifier which identifies a
national or geographic grouping of publishers;
Publisher identifier which identifies a particular
publisher within a group;
Title identifier which identifies a particular
title or edition of a title;
Check digit is the single digit at the end of the
ISBN which validates the ISBN."

--- Evan Reese <mentat1@xxxxxxxxxxxxxx> wrote:

> I have a book with an ISBN with an X at the end of
> it, such as:
> ISBN: 0-7564-0326-X
>
> I have encountered this before, but not often, and
> was wondering if anyone here knows what the X
> signifies.
>
>
> Thanks.
>

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