Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Data
Imports System.Drawing
Imports System.Linq
Imports System.Text
Imports System.Windows.Forms


Namespace WindowsFormsApplication1


    Public Partial Class Form1
        Inherits Form
        Private op As Integer = 0, opx As Integer = 0, opd As Integer = 0, opm As Integer = 0, opdeci As Integer = 0, opeq As Integer = 0, _
            equop As Integer = 0

        Private a As Double = 0, b As Double = 0, c As Double = 0

        Public Sub New()
            InitializeComponent()
        End Sub

        Private Sub textBox1_TextChanged(sender As Object, e As EventArgs)

        End Sub

        Private Sub button1_Click(sender As Object, e As EventArgs)

            If ansbox.Text.Length > 0 Then
                ansbox.Text = ansbox.Text.Substring(0, ansbox.Text.Length - 1)
            End If
            If ansbox.Text.Length = 0 Then
                ansbox.Text = "0"
                opdeci = 0
            End If

        End Sub

        Private Sub num1_Click(sender As Object, e As EventArgs)
            If ansbox.Text = "0" Then
                ansbox.Text = "1"
            Else
                ansbox.AppendText("1")
            End If

            If op <> 0 Then
                ansbox.Text = "1"
                op = 0
                opdeci = 0
            End If


        End Sub

        Private Sub num2_Click(sender As Object, e As EventArgs)
            If ansbox.Text = "0" Then
                ansbox.Text = "2"
            Else
                ansbox.AppendText("2")
            End If

            If op <> 0 Then
                ansbox.Text = "2"
                op = 0
                opdeci = 0
            End If
        End Sub

        Private Sub num3_Click(sender As Object, e As EventArgs)
            If ansbox.Text = "0" Then
                ansbox.Text = "3"
            Else
                ansbox.AppendText("3")
            End If

            If op <> 0 Then
                ansbox.Text = "3"
                op = 0
                opdeci = 0
            End If
        End Sub

        Private Sub num4_Click(sender As Object, e As EventArgs)
            If ansbox.Text = "0" Then
                ansbox.Text = "4"
            Else
                ansbox.AppendText("4")
            End If

            If op <> 0 Then
                ansbox.Text = "4"
                op = 0
                opdeci = 0
            End If
        End Sub

        Private Sub num5_Click(sender As Object, e As EventArgs)
            If ansbox.Text = "0" Then
                ansbox.Text = "5"
            Else
                ansbox.AppendText("5")
            End If

            If op <> 0 Then
                ansbox.Text = "5"
                op = 0
                opdeci = 0
            End If
        End Sub

        Private Sub num6_Click(sender As Object, e As EventArgs)
            If ansbox.Text = "0" Then
                ansbox.Text = "6"
            Else
                ansbox.AppendText("6")
            End If

            If op <> 0 Then
                ansbox.Text = "6"
                op = 0
                opdeci = 0
            End If
        End Sub

        Private Sub num7_Click(sender As Object, e As EventArgs)
            If ansbox.Text = "0" Then
                ansbox.Text = "7"
            Else
                ansbox.AppendText("7")
            End If

            If op <> 0 Then
                ansbox.Text = "7"
                op = 0
                opdeci = 0
            End If
        End Sub

        Private Sub num8_Click(sender As Object, e As EventArgs)
            If ansbox.Text = "0" Then
                ansbox.Text = "8"
            Else
                ansbox.AppendText("8")
            End If

            If op <> 0 Then
                ansbox.Text = "8"
                op = 0
                opdeci = 0
            End If
        End Sub

        Private Sub num9_Click(sender As Object, e As EventArgs)
            If ansbox.Text = "0" Then
                ansbox.Text = "9"
            Else
                ansbox.AppendText("9")
            End If

            If op <> 0 Then
                ansbox.Text = "9"
                op = 0
                opdeci = 0
            End If
        End Sub

        Private Sub num0_Click(sender As Object, e As EventArgs)
            If ansbox.Text = "0" Then
                ansbox.Text = "0"
            Else
                ansbox.AppendText("0")
            End If

            If op <> 0 Then
                ansbox.Text = "0"
                op = 0
                opdeci = 0
            End If
        End Sub

        Private Sub button2_Click(sender As Object, e As EventArgs)
            ansbox.Text = "0"

        End Sub

        Private Sub sum_Click(sender As Object, e As EventArgs)

            If equop <> 1 Then
                prodcode()
                divcode()
                If opm = 0 Then
                    a += Double.Parse(ansbox.Text)
                Else
                    mincode()
                End If

                ansbox.Text = a.ToString()

                op += 1
            End If
            equop = 0
            opeq = 3
        End Sub

        Private Sub prod_Click(sender As Object, e As EventArgs)
            If equop <> 1 Then
                divcode()
                If opx = 0 Then
                    b = Double.Parse(ansbox.Text)
                Else
                    b = b * Double.Parse(ansbox.Text)
                End If


                op += 1
            End If
            opx = 1
            opeq = 1
        End Sub

        Private Sub button3_Click(sender As Object, e As EventArgs)
            ansbox.Text = "0"
            a = 0
            b = 0
            c = 0
            opx = 0
            op = 0
            opd = 0
            opm = 0
            opdeci = 0
            opeq = 0
            equop = 0
        End Sub

        Private Sub deci_Click(sender As Object, e As EventArgs)
            If opdeci = 0 Then
                If ansbox.Text = "0" Then
                    ansbox.Text = "0."
                Else
                    ansbox.AppendText(".")
                End If

                If op <> 0 Then
                    ansbox.Text = "."
                    op = 0
                End If
            End If
            opdeci = 1
        End Sub



        Private Sub div_Click(sender As Object, e As EventArgs)
            If equop <> 1 Then
                prodcode()
                If opd = 0 Then
                    c = Double.Parse(ansbox.Text)
                Else
                    c = c / Double.Parse(ansbox.Text)
                End If


                op += 1
            End If
            opeq = 2
            opd = 1
        End Sub



        Private Sub min_Click(sender As Object, e As EventArgs)
            If equop <> 1 Then
                prodcode()
                divcode()

                If opm = 0 Then
                    a += Double.Parse(ansbox.Text)
                Else

                    a -= Double.Parse(ansbox.Text)
                    opm = 0
                End If

                ansbox.Text = a.ToString()



                op += 1
            End If
            equop = 0
            opeq = 4
            opm += 1
        End Sub



        Private Sub sqrt_Click(sender As Object, e As EventArgs)
            ansbox.Text = Math.Sqrt(Double.Parse(ansbox.Text)).ToString()
        End Sub

        Private Sub overx_Click(sender As Object, e As EventArgs)
            Dim temp As Double
            temp = Double.Parse(ansbox.Text)
            temp = 1 / temp
            ansbox.Text = temp.ToString()

        End Sub

        Private Sub pom_Click(sender As Object, e As EventArgs)
            ansbox.Text = "-" + ansbox.Text
        End Sub

        Private Sub equals_Click(sender As Object, e As EventArgs)
            Select Case opeq
                Case 1
                    If a <> 0 Then
                        a = a * Double.Parse(ansbox.Text)
                        ansbox.Text = a.ToString()
                    Else
                        b = b * Double.Parse(ansbox.Text)
                        ansbox.Text = b.ToString()
                        a = b
                    End If

                    Exit Select
                Case 2
                    If a <> 0 Then
                        a = a / Double.Parse(ansbox.Text)
                        ansbox.Text = a.ToString()
                    Else
                        c = c / Double.Parse(ansbox.Text)
                        ansbox.Text = c.ToString()
                        a = c
                    End If

                    Exit Select
                Case 3
                    a = a + Double.Parse(ansbox.Text)
                    ansbox.Text = a.ToString()
                    Exit Select
                Case 4
                    a = a - Double.Parse(ansbox.Text)
                    ansbox.Text = a.ToString()
                    Exit Select
            End Select
            op += 1
            equop = 1

        End Sub

        Private Sub prodcode()
            If opx <> 0 Then
                b = b * Double.Parse(ansbox.Text)
                ansbox.Text = b.ToString()
                b = 0
                opx = 0
            End If

        End Sub
        Private Sub divcode()
            If opd <> 0 Then
                c = c / Double.Parse(ansbox.Text)
                ansbox.Text = c.ToString()
                c = 0
                opd = 0
            End If
        End Sub
        Private Sub mincode()
            If opm <> 0 Then
                a -= Double.Parse(ansbox.Text)
                opm = 0
            End If
        End Sub
    End Class
End Namespace