ISBN-13 Assignment - C Programming Source Code

An International Standard Book Number (ISBN) is a unique number assigned to each book. ISBN-13 has thirteen digits in 5 parts which the last digit is “check digit”. The check digit is base ten, and can be 0-9. To compute a missing check digit, each digit, from the left to right, is alternatively multiplied by 1 or 3.Then, the sum of these

products should be divided by 10 to find the remainder ranging from 0 to 9. Finally, the check digit can be found by subtracting the remainder from 10, that leaves a result from 1 to 10.

For example, take the ISBN 978-0-306-40615-? :

1. a)  Firstcalculatesumofproducts:9×1+7×3+8×1+0×3+3×1+0×3+6×1+4×3 + 0×1 + 6×3 + 1×1 + 5×3 = 93
   
2. b)  Remainder upon dividing by 10 is 3.
   
3. c)  Remainder is subtracted from 10.
   
4. d)  Check digit is 7 (10 - 3). 
   

int main()

{

// variable declaration

                unsigned long long int isbn, copyISBN;

                int count = 1, sum = 0, remainder, digit, checkDigit;

// accept user input

                printf("Enter the first twelve digits of an ISBN-13: ");

                scanf("%llu", &isbn);

   

                // copy this isbn to copyISBN

                copyISBN = isbn;

                // loop until copyISBN > 0

                while (copyISBN > 0)

                {

                                // get last digit of copyISBN

                               digit = copyISBN % 10;

                               // if even then multiply by one

                             if (count % 2==0)

                               {

                                               sum = sum + (digit * 1);

                                               count = 1;

                               }

                               // else multiply by 3

                               else

                               {

                                               sum = sum + (digit * 3);

                                               count = 2;

                               }

                               // divide copyISBN by 10

                               copyISBN = copyISBN / 10;

                }

                // find remainder

                remainder = sum % 10;

                // find checkDigit

                checkDigit = 10 - remainder;

                // print output

                printf("Check Digit: %d", checkDigit);

                return 0;

}