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Can we use downCasting here ? . Converting a base-class pointer (reference) to a derived-class pointer (reference) is called downcasting. Downcasting is not allowed without an explicit type cast.The downcasting in the above line can lead to an unsafe operation.C++ provides a special explicit cast called dynamic_cast that performs this conversion
Base * b = new Base();
derived * d = dynamic_cast<derived * >(b);

Base class pointer can pointer to the derived the class (in the case of public inheritance) and not the other way around. The derived classes might have moe data members and functions that the base class might not have and it is just no the right thing to do.

@ ketan :
this is relevant to c++
Base is the parent class and Derived is the child class ..

C++ supports up-casting i.e. assigning the derived class object's address to base class pointer. The opposite of that , i.e. down-casting is not possible. Because the size of derived class object is always greater than or equal to that of base class, and so if any pointer arithmetic would cause unexpected results.

The reason for this restriction is that the is-a relationship is not, in most of the cases, symmetric. A derived class could add new data members, and the class member functions that used these data members wouldn't apply to the base class. so if base class doesn't know anything about child class then how he behave like child class.