As you may know, most any book that you borrow or buy has an International Standard Book Number, otherwise known as an ISBN or ISBN-10, “a 10-digit number that uniquely identifies books and book-like products published internationally.” Books published since 2007 might also have an ISBN-13, a 13-digit number with a similar purpose, but never mind those.
It turns out that the last of an ISBN-10’s digits is a “check digit,” otherwise known (in binary contexts) as a “checksum,” a number related mathematically to its preceding digits. ISBN-10s’ digits are supposed to adhere to a formula, not unlike credit card numbers, and this check digit allows you to check whether an ISBN-10’s other nine digits are (most likely) valid without having to check, say, a database of books.
You are going to create a program named isbn.c which prompts for a user to input an ISBN number, and which will respond YES or NO depending whether or not it is a valid number.
When you are finished, make sure to visit the new page below, how to submit.
Program Spec Problem 1-7: ISBN