text: #ifndef MAINWINDOW_H
  #define MAINWINDOW_H
  
  #include <QMainWindow>
  
  QT_BEGIN_NAMESPACE
  namespace Ui { class MainWindow; }
  QT_END_NAMESPACE
  
  class MainWindow : public QMainWindow
  {
      Q_OBJECT
  
  public:
      MainWindow(QWidget *parent = 0);
      ~MainWindow();
  
  private:
      Ui::MainWindow *ui;
  
  private slots:
      void NumPressed();
      void MathButtonPressed();
      void EqualButtonSign();
      void ChangeNumberSign();
      void AcPressed();
  };
  #endif // MAINWINDOW_H
  