C++ file extensions:

• .cpp
• .CC
• .cxx

C++ header file extensions

• .hpp
• .h
• hxx

The recommended extensions are .cpp and .hpp

• The selection of a file extensions usually comes down to preference or versions of software you're using

The output of the compiled code comes out as a .o file

Preproccesed C++ Source Files have a .ii file extension

A class in C++ is a user-defined type or data structure declared with any of the keywords class, struct, or union

• By default access to members of a C++ class declared with the keyword class is private. The private members are not accessible outside the class; they can be accessed only through member functions of the class
• The public members form an interface to the class and are accessible outside the class.

Member functions are the functions, which have their declaration inside the class definition and works on the data members of the class. The definition of member functions can be inside or outside the definition of class.

• if its defined outside the class, use the scope resolution :: operator along with class name along with function name.