Introduction to OOP: Chapter 7: Inheritance
Practical Meaning of Inheritance
Data areas and behavior defined in a parent class are accessible
from within a child class.
Data areas and behavior of a child class are an extension (strictly larger)
than the data areas and behavior of parent classes.
A child class is in a certain sense both an extension and a restriction of
the parent class.
Intro OOP, Chapter 7, Slide 5