Silvio:

There are several ways to calculate check digits. Do a quick search on the internet of "check digit". I'm sure you will find what you are looking for.

--Paul

>Many years ago, more than I care to remember, I used to program accounting machines. One thing all our "programs" had was a check digit appended at the end of numeric codes so that it was easy to detect misstypings. I cannot remember how those check digits were calculated but it had to be very simple: only the most expensive machines could multiply or divide. Anybody knows how the check digit was calculated? I am taking a few days off, the first in several months, and I know that not having the answer risks spoiling the fun.
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>Silvio