# Talk:Check digit

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Still to be added is a discussion of the Verhoeff check digit scheme. See the marist.edu link.

16:06, 7 February 2006 (UTC)69.74.32.122 16:06, 7 February 2006 (UTC) I agree. Verhoeff is a little in depth (not too much though). And there are a few ways to calculate a Verhoeff check which all have a similar effect. The biggest difference is the σ (sigma) function. I've encountered two commonly used functions to transform digits in addition to the universally used dihedral group transformation.

Daniel 16:06, 7 February 2006 (UTC)69.74.32.122 16:06, 7 February 2006 (UTC)

## Contents

I'm sorry that I do not have time to correct this page, but there are several major errors:

In the ISBN example the weights are applied from the left most digit, starting with a weight of 1. Weights should be applied from the RIGHTMOST digit, starting with a weight of 2. This is because the check digit actually assumes a weight of 1, and is in fact the complement of the modulo 11 arithmetic remainder (i.e. 134 modulo 11 = 12 R 1, so the check digit is 11 - 2 = 9). When the ISBN code is checked for integrity the whole code, including the check digit, is used in the calculation and will produce an answer of 0 if valid.

The algorithm at the bottom of the article does not work, unfortunately I csnnot immediately see what it should be. —The preceding unsigned comment was added by 210.3.39.30 (talk) 02:46, 15 February 2007 (UTC).

## Control number

Is this the same as a control number?

Not completly, I think a control number can be a more complex than just a check digit. See here: http://glossary.ippaper.com/default.asp?req=knowledge/article/211 Gs1mo 21:00, 16 May 2007 (UTC)

## Another example of check digits

International Bank Account Numbers also contain check digits?

UK VAT numbers also have check numbers and this can be a way of cehcikng the bone fides of a company, perhaps someone who knows it could add it here?85.234.151.89 (talk) 19:07, 19 December 2009 (UTC)

## Orphaned References

Contemporary Abstract Algebra by Joseph Gallian, 5th edition, Houghton Mifflin, 2002, pp. 9-14.

"Modular Arithmetic in the Marketplace", by Joseph Gallian and Steven Winters, in The American Mathematical Monthly, Vol. 95, No. 6, 1988, pp. 548-551.

I don't see where these were being used in the article. I added a reference to EAN-13 check digit computation to the article. I also found a reference to the documentation for ISBN-10 check digit computation, but it is not public domain so I did not add this reference to the article at this time: http://www.lac-bac.gc.ca/iso/tc46sc9/2108.htm Calebb (talk) 07:28, 22 May 2008 (UTC)