Calc_VB

Option Explicit
Dim a, b, c As Single, j As Integer, k As Boolean
Private Sub cls_Click()
    xs.Text = ""
    dot.Enabled = True
    a = 0
End Sub
Private Sub dot_Click()
    If k Then k = False: xs.Text = "0"
    xs.Text = xs.Text + "."
    dot.Enabled = False
End Sub

Private Sub dy_Click()
    k = True
    b = Val(xs.Text)
    Select Case j
        Case 0
            c = a + b
        Case 1
            c = a - b
        Case 2
            c = a * b
        Case 3
            If b <> 0 Then c = a / b
        Case 4
            If b <> 0 Then c = a Mod b
    End Select
    xs.Text = c
End Sub

Private Sub exit_Click()
    Unload Me
    Form1.Show
End Sub

Private Sub Form_Load()
    k = False
End Sub

Private Sub js_Click(Index As Integer)
    k = True
    a = Val(xs.Text)
    j = Index
    dot.Enabled = True
End Sub
Private Sub num_Click(Index As Integer)
    If k Then k = False: xs.Text = "0"
    xs.Text = xs.Text & CStr(Index)
End Sub
Private Sub xs_Change()
    If Len(xs.Text) = 2 And Left(xs.Text, 1) = "0" And Right(xs.Text, 1) <> "." Then xs.Text = Right(xs.Text, 1)
End Sub