As an addendum, I highly recommend not reading decade old source code like this as an example of modern C++. C++11/14 have changed the language so much for the

As an addendum, I highly recommend not reading decade old source code like this as an example of modern C++. C++11/14 have changed the language so much for the better that anything targeting C++03 should be ignored for new projects and especially for new learners. Also, avoiding Boost and Qt early on is also a good idea. Both have tremendous stylistic and design differences from ISO C++ and while the language supports all of them when using the Boost libraries and Qt toolkit you need to shift mindset entirely in how you are writing code to match the backing architecture. Learn the core language first.