Game Programming using Qt 5 Beginner's Guide - Second Edition

Have a go hero – A GUI for the Caesar cipher

You can combine what you already know by implementing a full-blown GUI application that is able to encrypt or decrypt files using the Caesar cipher QIODevice class that we just implemented. Remember that QFile is also QIODevice, so you can pass its pointer directly to setBaseDevice().

This is just a starting point for you. The QIODevice API is quite rich and contains numerous methods that are virtual, so you can reimplement them in subclasses.