I have provided a brief introduction to the all three categories of the Gang of Four Design Patterns in this article.  The reader should be well aware of when to use which pattern in designing the software.  Recognizing the feature and benefit of a particular pattern is of utmost importance when implementing it.  The best advantage that can be gained from using these patterns is by applying the right type of pattern at the right place in the design.  Stay tuned for more articles in which I would like to provide a detailed know-how on each and every pattern with sample code examples in each case for better understanding of a design pattern, its intent and applicability.  I welcome your comments and suggestions.  Happy reading!