Public Class frmCalculator
    Dim decNum1 As Decimal
    Dim decNum2 As Decimal
    Dim bytSignState As Byte
    Dim bytNumState As Byte
    Dim decResult As Decimal

    Private Sub btnExit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnExit.Click
        Me.Close()
    End Sub

    Private Sub btnClear_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClear.Click
        txtBox.Text = ""
        decNum1 = 0
        decNum2 = 0
        decResult = 0
        bytNumState = 0
    End Sub

    Private Sub btn0_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn0.Click
        If bytNumState = 0 Then
            decNum1 = txtBox.Text & 0
            txtBox.Text = CStr(decNum1)
            'bytNumState += 1
        Else
            decNum2 = txtBox.Text & 0
            txtBox.Text = CStr(decNum2)
        End If
        
    End Sub

    Private Sub btn1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn1.Click
        If bytNumState = 0 Then
            decNum1 = txtBox.Text & 1
            txtBox.Text = CStr(decNum1)
            'bytNumState += 1
        Else
            decNum2 = txtBox.Text & 1
            txtBox.Text = CStr(decNum2)
        End If
    End Sub

    Private Sub btn2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn2.Click
        If bytNumState = 0 Then
            decNum1 = txtBox.Text & 2
            txtBox.Text = CStr(decNum1)
            'bytNumState += 1
        Else
            decNum2 = txtBox.Text & 2
            txtBox.Text = CStr(decNum2)
        End If
    End Sub

    Private Sub btn3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn3.Click
        If bytNumState = 0 Then
            decNum1 = txtBox.Text & 3
            txtBox.Text = CStr(decNum1)
            'bytNumState += 1
        Else
            decNum2 = txtBox.Text & 3
            txtBox.Text = CStr(decNum2)
        End If
    End Sub

    Private Sub btn4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn4.Click
        If bytNumState = 0 Then
            decNum1 = txtBox.Text & 4
            txtBox.Text = CStr(decNum1)
            'bytNumState += 1
        Else
            decNum2 = txtBox.Text & 4
            txtBox.Text = CStr(decNum2)
        End If
    End Sub

    Private Sub btn5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn5.Click
        If bytNumState = 0 Then
            decNum1 = txtBox.Text & 5
            txtBox.Text = CStr(decNum1)
            'bytNumState += 1
        Else
            decNum2 = txtBox.Text & 5
            txtBox.Text = CStr(decNum2)
        End If
    End Sub

    Private Sub btn6_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn6.Click
        If bytNumState = 0 Then
            decNum1 = txtBox.Text & 6
            txtBox.Text = CStr(decNum1)
            'bytNumState += 1
        Else
            decNum2 = txtBox.Text & 6
            txtBox.Text = CStr(decNum2)
        End If
    End Sub

    Private Sub btn7_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn7.Click
        If bytNumState = 0 Then
            decNum1 = txtBox.Text & 7
            txtBox.Text = CStr(decNum1)
            'bytNumState += 1
        Else
            decNum2 = txtBox.Text & 7
            txtBox.Text = CStr(decNum2)
        End If
    End Sub

    Private Sub btn8_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn8.Click
        If bytNumState = 0 Then
            decNum1 = txtBox.Text & 8
            txtBox.Text = CStr(decNum1)
            'bytNumState += 1
        Else
            decNum2 = txtBox.Text & 8
            txtBox.Text = CStr(decNum2)
        End If
    End Sub

    Private Sub btn9_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn9.Click
        If bytNumState = 0 Then
            decNum1 = txtBox.Text & 9
            txtBox.Text = CStr(decNum1)
            'bytNumState += 1
        Else
            decNum2 = txtBox.Text & 9
            txtBox.Text = CStr(decNum2)
        End If
    End Sub

    Private Sub btnPlus_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnPlus.Click
        decNum1 = CDec(txtBox.Text)
        txtBox.Text = ""
        bytSignState = 1
        bytNumState += 1
    End Sub

    Private Sub btnMinus_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnMinus.Click
        decNum1 = CDec(txtBox.Text)
        txtBox.Text = ""
        bytSignState = 2
        bytNumState += 1
    End Sub

    Private Sub btnMult_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnMult.Click
        decNum1 = CDec(txtBox.Text)
        txtBox.Text = ""
        bytSignState = 3
        bytNumState += 1
    End Sub

    Private Sub btnDiv_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDiv.Click
        decNum1 = CDec(txtBox.Text)
        txtBox.Text = ""
        bytSignState = 4
        bytNumState += 1
    End Sub

    Private Sub btnCalc_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCalc.Click
        decNum2 = CDec(txtBox.Text)
        txtBox.Text = ""
        If bytSignState = 1 Then
            decResult = decNum1 + decNum2
        ElseIf bytSignState = 2 Then
            decResult = decNum1 - decNum2
        ElseIf bytSignState = 3 Then
            decResult = decNum1 * decNum2
        ElseIf bytSignState = 4 Then
            decResult = decNum1 / decNum2
        End If
        txtBox.Text = CStr(decResult)
    End Sub

    Private Sub btnPoint_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnPoint.Click
        If CStr(txtBox.Text).IndexOf(".") = -1 Then
            txtBox.Text = txtBox.Text & "."
        End If
    End Sub

    Private Sub btnSign_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSign.Click
        If bytNumState = 0 Then
            decNum1 = 0 - decNum1
            txtBox.Text = CStr(decNum1)
        Else
            decNum2 = 0 - decNum2
            txtBox.Text = CStr(decNum2)
        End If
    End Sub

    Private Sub frmCalculator_KeyPress(ByVal KeyAscii As Integer)
        txtBox.Text = CStr(KeyAscii)
    End Sub
End Class