Chapter 4, Problem 6E

Account numbers sometimes contain a check digit that is the result of a mathematical calculation. The inclusion of the digit in an account number helps ascertain whether the number is a valid one. Write an application named CheckDigit that asks a user to enter a four-digit account number and determines whether it is a valid number. The number is valid if the fourth digit is the remainder when the number represented by the first three digits of the four-digit number is divided by 7. For example, 7770 is valid, because 0 is the remainder when 777 is divided by 7.

The next problems rely on the generation of a random number. You can create a random number that is at least mi n but less than max using the following statements:

Random ranNumberCenerator = new Random();

int randomNumber;

randomNumber = ranNumberGenerator .Next(min, max);