What is Object Oriented Programming (OOP)?

By Tony Marston
2007-01-30


What is an Object Oriented language?
A computer language can be aid to be Object Oriented if it provides support for the following:

Class	A class is a blueprint, or prototype, that defines the variables and the methods common to all objects of a certain kind.
Object	An instance of a class. A class must be instantiated into an object before it can be used in the software. More than one instance of the same class can be in existence at any one time.
Encapsulation	The act of placing data and the operations that perform on that data in the same class. The class then becomes the 'capsule' or container for the data and operations.
Inheritance	The reuse of base classes (superclasses) to form derived classes (subclasses). Methods and properties defined in the superclass are automatically shared by any subclass.
Polymorphism	Same interface, different implementation. The ability to substitute one class for another. This means that different classes may contain the same method names, but the result which is returned by each method will be different as the code behind each method (the implementation) is different in each class.

A class defines (encapsulates) both the properties (data) of an entity and the methods (functions) which may act upon those properties. Neither properties or methods which can be applied to that entity should exist outside of that class definition.

Tutorial Pages:
» Introduction
» What OOP is NOT
» What is an Object Oriented language?
» What OOP is
» The difference between OOP and non-OOP
» Practical Examples
» Conclusion
» References

Related Tutorials: » Web Database Access from Desktop Applications » CubeCart 3.0 Installation and Configuration » PHP Site Search Made Easy » Installing and Configuring Drupal 6.1 » Desktop Application Development with PHP-GTK » Installing PHP on Windows