Object-Oriented Programming

Structuring programs as objects that bundle state with behaviour — the dominant organizing idea of the 1990s and 2000s.

Core Principles & Analysis

• Smalltalk, from Alan Kay's group at Xerox PARC, defined the style; Simula 67 preceded it.
• Encapsulation, inheritance and polymorphism are the classic trio of features.
• Kay has said the essential idea was message passing between objects, not the classes.