# Category:Definitions/International Standard Book Numbers

This category contains definitions related to International Standard Book Numbers.
Related results can be found in Category:International Standard Book Numbers.

An international standard book number is an index number used to uniquely identify a published book.

### ISBN-$10$

The ISBN-$10$ format consists of a string of $9$ digits followed by a check digit in the set $\set {0, 1, \ldots, 9, X}$.

The check digit $d$ is calculated as follows.

Let $c$ be calculated as:

$c = \displaystyle \sum_{k \mathop = 1}^9 k d_k \pmod {11}$

where $d_k$ denotes the $k$th digit in the ISBN-$10$.

Then the check digit $d$ is defined as:

$d = \begin{cases} c & : c \le 9 \\ X &: c = 10 \end{cases}$

### ISBN-$13$

The ISBN-$13$ format consists of a string of $12$ digits followed by a check digit.

The check digit $d$ is calculated as:

$d = \displaystyle \sum_{k \mathop = 1}^{12} k d_k \pmod {10}$

## Pages in category "Definitions/International Standard Book Numbers"

The following 7 pages are in this category, out of 7 total.