Overview: 3 Object-Oriented Programming

Object-Oriented Programming (OOP) is a popular way of organizing programs, especially programs using graphical user interfaces. GEOS is an object-oriented system, programmed entirely in Object Assembly, a Geoworks innovation. This section describes the concepts behind OOP and how it is implemented in GEOS. If you are familiar with OOP concepts, you may skip this section; because terminology can differ from system to system, however, you will probably want to at least skim the rest of the section. (A full discussion of GEOS messaging and object manipulation can be found in the GEOS Programming chapter.)

Object-Oriented Programming is simply a way to organize code and data differently from traditional procedural programming. Anything done with procedural programming can be done in an object-oriented way and vice versa. However, OOP offers several significant advantages over procedural programming:

Modularity
Especially in large systems, modularity can lead to cleaner, more manageable, and more easily expandable programs. OOP provides tight modularity with each component ( object ) having a strict API. This modularity also makes OOP systems ideal for the multithreaded environment of GEOS.
Simplicity
People interact with things individually. Each object in our environment has a certain set of characteristics and certain behaviors. OOP systems use this point of view as a foundation for programs that are easy to understand.
Efficiency
The efficient design of objects in an OOP system can lead to less repetition of reusable code. Several objects working independently may use the same code, thus reducing the impact on memory usage.
Reduction of code
Because functionality (functions, routines, etc.) is inherited by object types from other object types (known as classes), it doesn't have to implemented again and again. Instead, one version of the code can exist in a particular class and be inherited by other classes, thus reducing coding and debugging time.

Objects, Messages, and Methods

Classes and Inheritance

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