Public Class Form1
    'output methods
    Sub say(ByVal s As String)
        'output a string to the listbox
        Me.output.Items.Add(s) 'display the string s in listbox

    End Sub



    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        'divide, but check for div by zero. output result (or err msg)

        Dim a, b As Double          'first and second input
        Dim result As Double        'result of operation
        Dim msg As String           ' the output string will be composed here
        Dim what As String = "quotient"     'result type

        '1 input: get a,b
        a = CDbl(Me.txtfirst.Text)
        b = CDbl(Me.txtsecond.Text)

        '2 process: compute the quotient, but first check for /0
        If (b <> 0) Then


            result = a / b
            msg = "the " & what & " is " & Format(result)
        Else
            msg = "!! denominator cannot be zero!"

        End If
        '3 output: show the answer
        say(msg)

    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        'multiply 2 #s output result (or err msg)

        Dim a, b As Double          'first and second input
        Dim result As Double        'result of operation
        Dim msg As String           ' the output string will be composed here
        Dim what As String = "product"     'result type

        '1 input: get a,b
        a = CDbl(Me.txtfirst.Text)
        b = CDbl(Me.txtsecond.Text)

        '2 process: compute the product



        result = a * b
        msg = "the " & what & " is " & Format(result)

        '3 output: show the answer
        say(msg)
    End Sub

    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        ' add 2 #s . output result.
        Dim a, b As Double          'first and second input
        Dim result As Double        'result of operation
        Dim msg As String           ' the output string will be composed here
        Dim what As String = "sum "     'result type

        '1 input: get a,b
        a = CDbl(Me.txtfirst.Text)
        b = CDbl(Me.txtsecond.Text)
        '2 process: add a,b
        result = sum(a, b)
        msg = "the " & what & "is " & Format(result)
        '3 output: show the answer

        say(msg)

    End Sub
    Function sum(ByVal a As Double, ByVal b As Double) As Double
        'return the sum of a and b
        Dim result As Double
        result = a + b
        Return result

    End Function

    Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
        ' subtract 2 #s . output result.
        Dim a, b As Double          'first and second input
        Dim result As Double        'result of operation
        Dim msg As String           ' the output string will be composed here
        Dim what As String = "difference "     'result type

        '1 input: get a,b
        a = CDbl(Me.txtfirst.Text)
        b = CDbl(Me.txtsecond.Text)
        '2 process: subtract a,b
        result = a - b
        msg = "the " & what & "is " & Format(result)
        '3 output: show the answer

        say(msg)
    End Sub



    Private Sub Button6_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button6.Click
        Me.Close()

    End Sub

    Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click

        txtfirst.Clear()
        txtsecond.Clear()
        Me.output.Items.Clear()






    End Sub
End Class