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This resource checks whether a given 10-digit ISBN (International Standard Book Number) is valid and displays the information held on the number. It also give you the opportunity of going to the relevant Amazon page and or earching for the number through Google.
The last of the ten digits (which can also be an ‘X’ as well as the numbers 1–9) is called a ‘checksum’ digit which a computer can use to check whether the other 9 numbers are correct.
The program checks whether an ISBN is valid by starting on the left and multipling the first digit by 10, adding the second digit multipled by 9, then the third digit multiplied by 8 and so on... until you reach the last digit which is added to the running total. If the last digit is an ‘X’, you add 10 ten to the total. The total is divided by 11 and, if there is no remainder, the ISBN is valid.
