#include using namespace Upp; struct MyAppWindow : TopWindow { Button button; MyAppWindow() { Title("My application with button"); Add(button.LeftPos(10, 200).TopPos(10, 60)); button.SetLabel("Click me!"); button << [=] { PromptOK("You have clicked the button!"); }; } }; GUI_APP_MAIN { MyAppWindow app; app.Run(); }