dhelm@ibmpcug.co.uk (D Helm) (05/23/91)
>>In <1991May19.022623.2905@solbourne.com> imp@solbourne.com (Warner Losh) writes: >>Does anybody know the checksum procedure for ISBN book numbers? >1 * 1st digit + 2 * 2nd digit + 3 * 3rd digit + ... + 10 * 10th digit >must be divisible by 11. >Sometimes the last digit is an 'X'; that's a Roman digit with value 10. >Hans Mulder hansm@cs.kun.nl Almost - to calculate an ISBN checkdigit: From Left to Right take each digit and multiply by Weight factor. Test ISBN = 090169049 ISBN ISBN Weight Total Digit Digit Factor Position 1st 0 10 0 2nd 9 9 81 3rd 0 8 0 4th 1 7 7 5th 6 6 36 6th 9 5 45 7th 0 4 0 8th 4 3 12 9th 9 2 18 -------- Total 199 -------- Divide Total by 11 = 18 remainder 1 Subtract Remainder from 11 = 10 If the result = 0 - 9 then this is the check digit = result If the result = 10 then check digit = X. Hope this helps. Dave H. Disclaimer: I work for the company - they don't own me. -- Automatic Disclaimer: The views expressed above are those of the author alone and may not represent the views of the IBM PC User Group. --