In this program i want to use the private visibility mode how i use the the private visibility mode??? And what change is occur?

default visibility mode in c++ classes is private so in your class definition of Class A int a is private and in class B int b and c is private and if you want to specify private by your self you can write private : just like you wrote public: and the change occur is if data is private than it can only be accessible inside the class definition.

your ans is right but i use the private visibility and what change is occur in the program