Inheritance basics
A subclass inherits the methods of its superclass, but not its constructors. If no constructor is created in the subclass, it automatically receives a parameterless constructor.
Each constructor automatically calls the default constructor of its superclass. Only then are its own methods executed.
class Item {
// Upper class
};
class Book: public Item {
// Subclass inherits information from class Item
};
class Cd: public Item {
// Subclass inherits information from class Item
};