Design Patterns Explained: A New Perspective on Object-Oriented Design

Before The Object-Oriented Paradigm: Functional Decomposition

Let's start out by examining a common approach to software development. If I were to give you the task of writing code to access a description of shapes that were stored in a database and then display them, it would be natural to think in terms of the steps required. For example, you might think that you would solve the problem by doing the following:

1.	Locate the list of shapes in the database.
2.	Open up the list of shapes.
3.	Sort the list according to some rules.
4.	Display the individual shapes on the monitor.

You could take any one of these steps and further break down the steps required to implement it. For example, you could break down Step 4 as follows:

For each shape ...