ISSN Barcode Structure

1. The ISSN/ISBN number - printed above the barcode
2. Prefix - The prefix 977 is for ISSN, 978 for ISBN.
3. The ISSN/ISBN number minus the check digit - Only the first seven digits of the ISSN number appear in the bar code. The ISSN check digit is not represented.
4. Sequence variant - A two digit space is used to hold the number of times the issue price has changed since the bar code was first used on the publication.
5. The check digit
6. Two digit add-on - Issue number, usually 2/5 digits