when do we need virtual functions in c++
Virtual function In object-oriented programming, when a derived class inherits from a base class, an object of the derived class may be referred to via a pointer or reference of the base class type instead of the derived class type. If there are base class methods overridden by the derived class, the method actually called by such a reference or pointer can be bound either 'early' (by the compiler), according to the declared type of the pointer or reference, or 'late' (i.e., by the runtime system of the language), according to the actual type of the object referred to.
Return type In computer programming, the return type (or result type) defines and constrains the data type of the value returned from a subroutine or method.[1] In many programming languages (especially statically-typed programming languages such as C, C++, Java) the return type must be explicitly specified when declaring a function.