ptr_exs.cpp gives an example of how to use references.
Examples of the IntCell class where the instance variable is now a pointer to an integer.
In intcell_default.h the big three (destructor, copy constructor and operator=) functions are not defined -- the defaults are used instead.
In intcell_bigthree.h, we define the destructor, copy constructor and operator= functions.
In intcell_tester.cpp we create different IntCell variables using the copy constructor and the operator= function. Change which .h file is included to change which version of IntCell is used.