ISBN

• All books in the U.S. are assigned a number, the ISBN.
• This number is printed on the back cover of the book.
• Our text book has the ISBN below.
• The ISBN is coded to provide an error detection capability.
• Like in the USPS bar code, the last digit is a check digit.
• The check digit is computed as follows:
  • Multiply each of the first 9 digits of the ISBN by a weighting factor.
  • The weighting factor is 10 for the first digit, 9 for the second, etc.
  • Sum the products of digits and weighting factors.
  • Divide the sum by 11.
  • Subtract the remainder of the division from 11 to get the check digit.
  • If the check digit is 10, it is represented by X.

  

Figure 2.20: ISBN for textbook previously used in ECE 101.