add a top-level window widget

main.cc

@@ -1,9 +1,14 @@
 #include <QtGui>
 #include <QApplication>
+#include <QWidget>
 
 int main(int argc, char * argv[])
 {
     QApplication app(argc, argv);
+    QWidget window;
+    window.resize(600, 600);
+    window.show();
+    window.setWindowTitle("My Qt Application!");
 
     return app.exec();
 }