The C++ Program Structure
graphics.h is a library header file containing the declarations of graphics functions and
variables used in function main().
ClassA.h is a user defined header file containing the declarations for ClassA
ClassB.h contains the declarations for ClassB
ClassA.cpp contains the definitions of the member functions of classA
ClassB.cpp contains the definition of the member functions of ClassB
Program_name.cpp contains the definition of of function main().