A Description of the Model-View-Controller User Interface Paradigm in the Smalltalk-80 System

This essay describes the Model-View-Controller (MVC) programming paradigm and methodology used in the Smalltalk-80TM programming system. MVC programming is the application of a three-way factoring, whereby objects of different classes take over the operations related to the application domain, the display of the application's state, and the user interaction with the model and the view. We present several extended examples of MVC implementations and of the layout of composite application views. The Appendices provide reference materials for the Smalltalk-80 programmer wishing to understand and use MVC better within the Smalltalk-80 system.