by the manufacturer. The product code immediately follows manufacturer code. The total length of manufacturer code plus product code should be 9 or 10 digits depending on the length of country code (2–3 digits). In ISBN, ISMN and ISSN, it uniquely identifies the publication from the same publisher; it should be used and allocated by the registered publisher in order to avoid creating gaps; however it happens that a registered book or serial never gets published and sold. Check digit The check digit is an additional digit, used to verify that a barcode has been scanned correctly. It is computed modulo 10, where the weights in the checksum calculation alternate 3 and 1. In particular, since the weights are relatively prime to 10, the EAN-13 system will detect all single digit errors. It also recognizes 90% of transposition errors (all cases, where the difference between adjacent digits is not 5). Calculation of checksum digit The checksum is calculated as sum of products – taking an alternating weight value (3 or 1) times the value of each data digit. The checksum digit is the digit, which must be added to this checksum to get a number divisible by 10 (i.e. the additive inverse of the checksum, modulo 10). See ISBN-13 check digit calculation for a more extensive description and algorithm. The Global Location Number(GLN) also uses the same method. Position – weight The weight at a specific position in the EAN code is alternating (3 or 1) in a way, that the final data digit has a weight of 3 (and thus the check digit has a weight of 1). All Global Trade Item Number (GTIN) and Serial Shipping Container Code (SSCC) codes meet the next rule: Numbering the positions from the right (code aligned to the right), the odd data digits are always weight of 3 and the even data digits are always weight of 1, regardless of the length of the code. Weights for 18-digit SSCC code and GTINs (GTIN-8, GTIN-12, GTIN-13, GTIN-14): Weights for EAN-13 code: Weights for EAN-8 code: Calculation examples For EAN-13 barcode 400638133393x, where x is the unknown check digit, (Stabilo Point 88 Art. No. 88/57), the check digit calculation is... {|class="wikitable" style="text-align: center" ! position | 12 || 11 || 10 || 9 || 8 || 7 || 6 || 5 || 4 || 3 || 2 || 1 |- ! first 12 digits