Structure of a 13-digit ISMN
From the beginning of the year 2008, all ISMNs shall consist of a 13-digit number composed of the following four elements:
| 979-0 | = | the prefix element 979-0 |
| 321 | = | a publisher element |
| 76543 | = | an item element |
| 1 | = | a check digit |
In front of the code there are always the letters ISMN, and the elements are separated from each other by a hyphen or a blank.
ISMN 979-0-321-76543-1
Prefix element
The first element is a 4-digit prefix. The first three digits of the ISMN prefix shall be "979" along to the Bookland code within the GS1 system. The element containing "979" shall be separated for display purposes by a hyphen from the fourth digit (0) of the ISMN prefix.
Publisher element
This code tells who the publisher is, and the length of the code varies depending on the publisher's title output.
Item element
This code identifies an edition of a certain publication and all formats in which it is published, for example a score, a miniature score, a set of the wind instrument parts, the oboe part etc. The length of this element is determined by the length of the publisher identifier.
Check digit
The check digit is automatically counted by the computer and at the same time it checks that the ISMN is correct. The calculating format is found in the User's manual under the title Construction of the ISMN.
