Example: 962-001-006-X (GroupID - PublisherID - Title - CheckDigit)
weighted sum
= 9*10 + 6*9 + 2*8 + 0*7 + 0*6 + 1*5 + 0*4 + 0*3 + 6*2 + X*1
= 187 (where X=10)
= 17 x 11
962-001-006-X is valid because the sum is divisible by 11.
| 1967 | ISBN established |
| 1976 | ISBN used in HK |
// validation check char isbn[11]="962001006X"; isbn[9] = toupper(isbn[9]); ... ok=0;