#include<qapplication.h>#include<qwidget.h>#include<qpushbutton.h>#include<qfont.h>#include<qlabel.h>class MyMainWin:public QWidget{  public:    MyMainWin();    private:    QPushButton *b1;    QLabel *label;};MyMainWin::MyMainWin(){//setMinimumSize(200,120);    //setMaximumSize(400,240);         setGeometry(100,100,200,120);   // b1=new QPushButton("Button 1",this);    b1=new QPushButton("Quit	",this);    b1->setGeometry(20,20,160,80);    b1->setFont(QFont("Times",18,QFont::Bold),true);        label=new QLabel(this);    label->setGeometry(20,110,180,50);    label->setText("If you click the buttonabove,\n		  the whole program will exit! ");    label->setAlignment(AlignCenter);}int main(int argc,char **argv){   QApplication a(argc,argv);     MyMainWin w;    a.setMainWidget(&w);    w.show();    a.exec();    }