This is the original source for most common design patterns that are used today. Although this book is rather old (1995) and has never been updated (the diagrams are still in a pre-UML “Object Modeling Techniques”), it should be present on every software-engineer’s bookshelf.

The information in this book constitutes essential knowledge. Even though, many software developers find that reading the book is tough, Mithun’s “Design Patterns” course provides a thorough and palatable overview of the material in the book. During this course all patterns described in it are addressed. The course has many examples that pertain to technical (control) applications, contrary to the book which gives almost exclusively examples from user interfaces. Due to the many examples and exercises offered during the course, it not only gives you sound knowledge on patterns, but also allows you to practice and improve your modeling skills.