Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        'This is my array variable, it will allow me to store data'
        Dim i As Integer
        'This is my second array variable, it does exactly the same job'
        Dim j As Integer
        'These are my other variables I will assign a value or scentence to'
        Dim Name As String
        Dim Postcode As String
        Dim NumberArray(7) As Integer
        Dim check_digit As Integer
        Dim total As Integer
        Dim cardnumber As Integer
        Dim expiredate As Date
        Dim time As Date
        'This code allows me to check the expirey date of the loyalty card'
        time = System.DateTime.Today
        expiredate = TextBox4.Text
        If expiredate < time Then
            MessageBox.Show("Your card is out of date")
            Stop
        End If

        'This assigns the text in TextBox3 as the Name'
        Name = (TextBox3.Text)
        'This assigns the text and numbers in TextBox2 as the Postcode'
        Postcode = (TextBox2.Text)
        'This assigns the numbers in Textbox1 as the card number'
        cardnumber = (TextBox1.Text)

        For i = 0 To 7
            NumberArray(i) = TextBox1.Text.Substring(i, 1)
        Next
        'This stores the 8th digit as check_digit'
        check_digit = NumberArray(7)
        'This will reverse the remaining 7 digits'
        Array.Reverse(NumberArray)

        For j = 0 To 6
            NumberArray(j) = TextBox1.Text.Substring(j, 1)
        Next
        'This multiplies the required numbers by 2'
        NumberArray(0) = NumberArray(0) * 2
        NumberArray(2) = NumberArray(2) * 2
        NumberArray(4) = NumberArray(4) * 2
        NumberArray(6) = NumberArray(6) * 2
        'If the multiplication answer is greater than 9 this code then takes away 9 from the answer'
        If NumberArray(0) > 9 Then
            NumberArray(0) = NumberArray(0) - 9
        End If
        If NumberArray(2) > 9 Then
            NumberArray(2) = NumberArray(2) - 9
        End If
        If NumberArray(4) > 9 Then
            NumberArray(4) = NumberArray(4) - 9
        End If
        If NumberArray(6) > 9 Then
            NumberArray(6) = NumberArray(6) - 9
        End If
        'This adds the altered numbers and the normal numbers together as well as the 8th digit(check_digit)'
        total = NumberArray(0) + NumberArray(1) + NumberArray(2) + NumberArray(3) + NumberArray(4) + NumberArray(5) + NumberArray(6) + check_digit
        'This checks if the total is directly divisible by ten'
        If total Mod 10 = 0 Then
            'This displays whetheror not the card is valid'
            MessageBox.Show("Name " & Name)
            MessageBox.Show("Postcode " & Postcode)
            MessageBox.Show("Your card Number " & cardnumber)
            MessageBox.Show(total)
            MessageBox.Show("Your loyalty card is valid ")

        ElseIf MessageBox.Show("Name " & Name) Then
            MessageBox.Show("Postcode " & Postcode)
            MessageBox.Show("Your card Number " & cardnumber)
            MessageBox.Show(total)
            MessageBox.Show("Your loyalty card is invalid ")

        End If



    End Sub
End Class