search for: tech_nn_check_digit

...eed to check that the NHS numbers in my database are valid. I''m storing them as ten-digit strings: the first nine are the identifier and the tenth is a check digit. There are four steps to calculating the check digit (from http://www.connectingforhealth.nhs.uk/systemsandservices/nsts/docs/tech_nn_check_digit.pdf): 1. multiply each of the first nine digits by a weighting factor (10 for the first digit, 9 for the second... 2 for the ninth) 2. sum the results of these multiplications 3. divide the total by 11 and establish the remainder 4. subtract the remainder from 11 to give the check digit. If th...