In this course, we won't delve into the full theory of object-oriented design. We'll concentrate on the pre-cursor of OO design: abstract data types (ADTs). A theory for the full object oriented approach is readily built on the ideas for abstract data types.
An abstract data type is a data structure and a collection of functions or procedures which operate on the data structure.
To align ourselves with OO theory, we'll call the functions and procedures methods and the data structure and its methods a class, i.e. we'll call our ADTs classes. However our classes do not have the full capabilities associated with classes in OO theory. An instance of the class is called an object . Objects represent objects in the real world and appear in programs as variables of a type defined by the class. These terms have exactly the same meaning in OO design methodologies, but they have additional properties such as inheritance that we will not discuss here.
It is important to note the object orientation is a design methodology. As a consequence, it is possible to write OO programs using languages such as C, Ada and Pascal. The so-called OO languages such as C++ and Eiffel (Eiffel is an object-oriented language based on Ada designed by Betrand Meyer. It provides formal support for pre-conditions by allowing a programmer to insert assert statements at appropriate points in his code. ) simply provide some compiler support for OO design: this support must be provided by the programmer in non-OO languages.
