Criteria:
1.	Add menu items that allow the user to request saving and loading 

2.	Add member functions to allow saving and separate ones for loading (fixed file name)

3.	Object-oriented approach; it must contain only member functions 

4.	main() which should do no more than create the first object

5.	All members must be private 

6.	Document properly the code you add, with neat structure

Hints:
1.	Decide on the classes you need, include a set of classes that implement the functionality of the code in such a way that they could be used by other developers 

2.	To establish suitable member functions, take into account the responsibilities of each class; for example, which class should perform the filtering operation? 

3.	Encapsulation dictates that, as far as possible, an object should be responsible for its own data 

4.	Use polymorphism only as appropriate. The general rule is that if an inbuilt operator matches the purpose of a member function then it should be overloaded. 

5.	Use inheritance only where necessary. Only if you can reasonable say that object A is a type of object B should A inherit from B. For example, a car is a type of vehicle, but a table isn’t a type of elephant (even if both normally have four legs).