dynamic polymorphism is run time polymorphism.it is 
implemented through virtual functions

in hirarchie, when sub class overrides the super class
metthod       
then we call that method using the super class reference
then which version of method is called is resolved at run
time based  on the object that the reference refers to is
called dynamic polymorphisum or dynamic binding.and also
called run time polymorphisum

there are two type polymorphism use in c++ first is static
and second is dynamic static polymorphism is function
overloading oprater overloading & dynamic is virtual function.

In Dynamic Polymorphism memory allocation will be at the 
run time for that perticular method which is implemented 
as polymorphism.

If binding is resolved at compilation time then it is said 
to be static polymorphism.
If binding is resolved at reun time then it is said to be 
dynamic polymorphism. to implement dynamic polymorphism, 
pointers and virtual functions are used.

There are two type of polymorphism i.e. 
    static(compiplation time) and
    Dynamic Polymorphism(Run Time).
In case of Static,
  derived class,Base class have same funcion name,the base 
class function will be called.
In Case of Dynamic Polymorphism,we can use virtual keyword 
in base class function and passing reference of derived 
class to the base class pointer, we can call the derived 
class function which is override.