QSettings settings("MyCompany", "MyApp"); // create a QSettings object with a unique key settings.setValue("window/size", QSize(800, 600)); // store a key-value pair QSize size = settings.value("window/size", QSize(640, 480)).toSize(); // retrieve a value with a default fallbackIn this example, a QSettings object is created with a key of "MyCompany/MyApp". The `setValue()` method is used to store a value with the key "window/size", which is set to a QSize of 800x600. The `value()` method is used to retrieve the value for that key, with a default fallback value of QSize(640, 480) if the key is not found. QSettings is part of the Qt Core library, which is included in the main Qt package.