Virtual destructors help in destroying objects without knowing their type. With the help of the virtual function mechanism, the appropriate destructor for the object is invoked. In the case of abstract classes, destructors can also be declared as pure virtual functions. For example, class A derives from class B. Then, on calling the derived class dynamically at the execution time, the destructor will first call the derived class that is class A, and then the base class that is class B.
It is important to note that theVirtual keyword, when used with the destructor, ensures the calling of all the derived and base class destructors and therefore helps in the proper execution and closing of the program.