checkdigit calculation for HP-17b

[Don Shepherd]

(07-26-2015 07:29 PM)Gerson W. Barbosa Wrote:  The interesting part is that I didn't need to look at the linked Wikipedia article before writing the equation, as I knew the algorithm since I was 14 or 15

Thanks Gerson.

I first learned about this algorithm when I started my job as a programmer in 1974 at the US Census Bureau (ah, those big Univac mainframes, I loved them).

I worked in the Economic Surveys division of the Bureau, and our main file had a record for each business establishment in the US. Every business had an Employer Identification number (EIN) assigned by either Social Security or IRS, probably IRS. In our programs, whenever we processed these files we had to verify the correct EIN, and part of that was to verify the checkdigit. I had never heard of the Luhn algorithm; my boss had probably never heard of it either, but he sure knew how it worked, and he explained it to me so I could implement it in every FORTRAN program I wrote.

I discovered it is also used on all credit cards in the US.

Don