Public Class Calculater
    Dim a, b, c As Integer
    Dim sign As String

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Textbox1.Text = 1 & Textbox1.Text
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Textbox1.Text = Textbox1.Text & 2
    End Sub

    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        Textbox1.Text = Textbox1.Text & 3
    End Sub

    Private Sub Button8_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button8.Click
        Textbox1.Text = Textbox1.Text & 4
    End Sub

    Private Sub Button7_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button7.Click
        Textbox1.Text = Textbox1.Text & 5
    End Sub

    Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
        Textbox1.Text = Textbox1.Text & 6
    End Sub

    Private Sub Button12_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button12.Click
        Textbox1.Text = Textbox1.Text & 7
    End Sub

    Private Sub Button11_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button11.Click
        Textbox1.Text = Textbox1.Text & 8
    End Sub

    Private Sub Button9_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button9.Click
        Textbox1.Text = Textbox1.Text & 9
    End Sub

    Private Sub Button16_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button16.Click
        Textbox1.Text = Textbox1.Text & 0
    End Sub

    Private Sub Button15_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button15.Click
        Textbox1.Clear()
        TextBox2.Clear()
        Textbox1.Focus()
    End Sub

    Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
        TextBox2.Text = Textbox1.Text + "+"
        a = Textbox1.Text
        Textbox1.Clear()
        Textbox1.Focus()
        sign = "+"
    End Sub

    Private Sub Button6_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button6.Click
        TextBox2.Text = Textbox1.Text + "-"
        a = Textbox1.Text
        Textbox1.Clear()
        Textbox1.Focus()
        sign = "-"
    End Sub

    Private Sub Button10_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button10.Click
        TextBox2.Text = Textbox1.Text + "*"
        a = Textbox1.Text
        Textbox1.Clear()
        Textbox1.Focus()
        sign = "*"
    End Sub

    Private Sub Button14_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button14.Click
        TextBox2.Text = Textbox1.Text + "/"
        a = Textbox1.Text
        Textbox1.Clear()
        Textbox1.Focus()
        sign = "/"
    End Sub

    Private Sub Button13_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button13.Click
        b = Textbox1.Text

        If sign = "+" Then
            Textbox1.Text = a + b
            TextBox2.Clear()
            TextBox2.Text = a.ToString + "+" + b.ToString
        ElseIf sign = "-" Then
            Textbox1.Text = a - b
            TextBox2.Clear()
            TextBox2.Text = a.ToString + "-" + b.ToString
        ElseIf sign = "*" Then
            Textbox1.Text = a * b
            TextBox2.Clear()
            TextBox2.Text = a.ToString + "*" + b.ToString
        ElseIf sign = "/" Then
            Textbox1.Text = a / b
            TextBox2.Clear()
            TextBox2.Text = a.ToString + "/" + b.ToString

        End If
    End Sub
End Class