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volvo part number suffix -how it really works 200 1993

Volvo part number check digits use what's called the Mod 10 Luhn algorithm developed by IBM in the early days of computing.

So close, Art, in your second example. You missed the final step of taking the resulting total of 27 and subtract it from 30 (the next highest multiple of 10) to get the check digit 3.

For any length of part number, you start from the right (working left) by replacing every odd digit with double of itself then add up every individual digit, followed by subtracting the result from the next highest modulus 10 number greater than or equal.
Eg. 123456 -> 1.2.3.4.5.6 -> 1.4.3.8.5.12 -> 1+4+3+8+5+1+2 -> 24 subtracted from 30 -> 6 -> 123456-6
(this an edited correction of my initial example)

Note that the algorithm is not affected by any leading zeroes before the part number which you may sometimes see in parts tables or on invoices.

This algorithm catches single digit transcription errors as well as most digit pair transposition errors. Modern check digit algorthms used with such things as UPC and bar codes are much more complicated and can catch multiple digit errors and even correct some types of errors.

The Luhn algorithm was popular because it was something that with a little practice humans could do without needing pen and paper. Such decimal digit arithmetic is a minor pain in the ass to program in binary computers, but it was considerably easier in IBM's COBOL programming language used in business/commercial applications that commonly stored numbers internally as decimal characters (rather than binary numbers) and had native string arithmetic (as it is called) so the Luhn algorithm was much easier to implement when passed off to a common library routine. This is giving me pleasant flashbacks to my days as a mainframe systems programmer writing such library routines in machine language to speed processing using the least amount of memory.

https://en.wikipedia.org/wiki/Luhn_algorithm
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now






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New Anyone know what these shocks are? [200][1993]
posted by  Epic2112  on Thu Jun 9 23:47 CST 2022 >


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