Algorithms! Modulus 11 algorithm.

The most difficult part of barcodes. Try understanding them and if you need help feel free to ask one of our group members! Have fun! Try solving for the different barcodes around you that use Mod11!

Numbers multiplied by their position starting from left to right.
ISBN-10 (10 digits):
10, 9, 8... 2

ISSN (8 digits):
8, 7, 6... 2

The position "1" is the check digit which is what we are solving for.

Then divide the sum by 11 and subtract the remainder from 11 and you get the check digit!