callback function:
callback function is any reference to executable code that is passed as an argument to another piece of code
https://en.wikipedia.org/wiki/Callback_(computer_programming)
C++ sample
- pointer.cpp
- function.cpp
- generic.cpp
- interface.cpp
- messenger.cpp
C sample
- func_address.c
- callback_func1.c
- callback_func2.c
- callback_func3.c