Release 10.1A: OpenEdge Getting Started:
Object-oriented Programming

Defining classes based on other classes

A class can extend another class by inheriting it. A class can inherit from at most one other class, which in turn can inherit from another class. This single inheritance model makes the non-private data members and methods of the super class appear as if they are part of the class being defined. If a class is marked as FINAL, it cannot be inherited and used as a super class for another class. The different classes that make up a class hierarchy are stored in separate class files, both in their source code form and their r-code form. However, at both compile time and run time, all the parts of a class hierarchy are treated as a single unit, and must all run in the same Progress session.