Ad. 1. Certainly no cross-platform way of doing that. I don’t use Windows, but I guess it would involve running something like “notepad fileToOpen.txt” in the terminal (console). In Qt, you can do that with QProcess.

Ad. 2. Connect button’s clicked() signal to a slot of your choice. In the slot, run:

Ad. 3. What do you mean by “work with files”? You mean you want to display only files? That would be strange. Anyway, what you probably need is to look into static members of QFileDialog (::getOpenFileName(), ::getOpenFileNames() etc.), or/ and the QFileDialog::FileMode flag.

Thanks for your reply. For the 2nd question, I meant with a already created *.ui file, not with a QMessageBox. Thanks!

The procedure is very similar. You have to include the UI header, initialise the object somewhere in your code (e.g. in main window’s constructor. This, again, can be done in many ways). Next, connect button’s signal to your slot, and there call: