The classes are useful as training examples for a C+++ tutorial, for novices in C++, or if you have to avoid the standard C++ library with its classes std::string and std::vector class for any reason. It contains basic functionality compatible with the std:: versions, more functions can easily be added.
Class my_string is based on original work by Christian Stigen Larsen, 2007.
It may happen in real projects that the std library must be avoided: I needed it
because of link problems...