Dim sss, i As Integer
        Dim ff As Boolean

        FileOpen(1, "C:\940303.sm", OpenMode.Input)
        Input(1, sss)
        FileClose()

        ff = True
        For i = 2 To sss - 1
            If (sss Mod i = 0) Then
                ff = False    'F=錯
            End If
        Next

        If ff = False Then
            TextBox4.Text = sss & "不是"
        Else
            TextBox4.Text = sss & "是"
        End If
    End Sub