Re: UPC Check Digit Algorithm

At 08:57 12/15/1998 -0500, Jeff Crosby wrote:
>
>Does anyone know where I can find the algorithm to calculate a UPC check
>digit?

Last time I had to figure this out, I left myself a trail of bread crumbs:

For a bar code with n digits (n is always an odd number)
where di is an interleave 2 of 5 bar code digit, k is the check digit
Scanning the bar code will return the series
    d1 d2 d3 ... dn k  
k can be calculated as
k = 2 * {d1 + d3 + d5 + ... + dn} + {d2 + d4 + d6 ... + dn-1}

For a UPC barcode, the formula is the same, but the multiplier is 3 instead
of 2. The first digit (number system) is included in the calculation (d1).
Pete Hall
peteh@inwave.com
http://www.inwave.com/~peteh
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