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As I know, EAN-13 system have seperate encodings for digits in the left group, usually mentioned as "even/odd parity encoding". And the barcode already have a 13th digit used as a check digit which has nothing to do with the concept "parity".

I want to know whether digits in the left group really carried information for "parity check" or the "parity" is introduced just for encoding the 1st digit? if it really carries a parity bit or something similar, does it have a definite "parity bit" in each binary sequence?

Pawel Gumiela
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Qutard
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1 Answers1

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The Check digit, a single checksum digit. The check digit 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 system will detect all single digit errors. But, since the difference of consecutive weights is even, the EAN system does not detect all adjacent transposition errors.

The checksum is calculated taking a varying weight value times the value of each number in the barcode to make a sum. The checksum digit is then the digit which must be added to this sum to get a number evenly divisible by 10 (i.e. the additive inverse of the sum, modulo 10)

The details of the algorithm are described on Wikipedia.

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Eric J.
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