#include "mainwindow.h" #include <QApplication> int main(int argc, char *argv[]) { QApplication a(argc, argv); bool ok = false; QString arg; if(argc > 1 && argv[1]){arg = argv[1]; arg.toInt(&ok,10);} int val = ok? arg.toInt() : 40; MainWindow w(val); w.show(); return a.exec(); }