Internal Documentation.
Note that you will be overriding three object methods in the Order class and at least one of those in the ShippedOrder class. In the ShippedOrder class you will also need to override the Quantity accessor/property. Don't forget about IComparable.
An example of program output might look like this:
Enter order number 500
Enter customer name Johnson
Enter quantity 2
Enter order number 200
Enter customer name Olson
Enter quantity 1
Enter order number 200
Sorry, the order number 200 is a duplicate.
Please reenter 100
Enter customer name Jensen
Enter quantity 8
Enter order number 300
Enter customer name Swensen
Enter quantity 2
Enter order number 400
Enter customer name Olafsun
Enter quantity 4

Summary:

ShippedOrder 100 Jensen 8 @$19.95 each. Shipping is $4.00
Total is $163.60
ShippedOrder 200 Olson 1 @$19.95 each. Shipping is $4.00
Total is $23.95
ShippedOrder 300 Swensen 2 @$19.95 each. Shipping is $4.00
Total is $43.90
ShippedOrder 400 Olafsun 4 @$19.95 each. Shipping is $4.00
Total is $83.80
ShippedOrder 500 Johnson 2 @$19.95 each. Shipping is $4.00
Total is $43.90

Total for all orders is $359.15
Press any key to continue . . .

Declaring a child class:
public class Fiction : Book //for extending classes, you must use a single colon between the derived class name and its base class name
{
private:
//put your private data members here!
public:
//put your public methods here!
}
NOTE: when you instantiate an object of Fiction child class, you will inherit all the data members and methods of the Book class.