Dim ISBN13(13), Total, CheckDigit As Integer
Console.Writeline("Digit." & i & "")
ISBN13(i) = Console.ReadLine()
Console.Writeline("Please enter a single digit")
ISBN13(i) = Console.ReadLine()
Loop Until ISBN13(i) < 10
Total = Total + ISBN13(i) * 3
Total = Total + ISBN13(i) * 1
Console.Writeline("Total number of 1 to 12 digits is " & Total)
CheckDigit = 10 - Total Mod 10
CheckDigit = CheckDigit - 10
Console.WriteLine("Check Digit ISBN13(13) is " & CheckDigit)
Console.WriteLine(ISBN13(i))