Over the years, software has become increasingly complicated. Now, software is not only used for mathematical calculations or simple create, read, update, and delete (CRUD) operations, we are employing it to carry out complex tasks, such as controlling rocket engines or managing huge amounts of data every day. Businesses from a vast range of sectors have started to adopt software systems, including banks, insurance companies, research institutes, education institutes, and government agencies. The higher the demand for software, the more people began to build careers in software development. From assembly-language programming came procedural programming, before the introduction of the era of Object-oriented programming (OOP), which is still the most popular model despite the emergence of other types of programming, such as functional programming. OOP has helped developers write good, modular software that is easy to maintain and extend. In this chapter, we are going to discuss some of the most important design principles and patterns that are followed by thousands of developers, and are going to cover the following topics:

• Design Principles in software development
• Different design patterns in software development
• Creational design patterns
• Behavioral design patterns
• Structural design patterns
• The Model-View-Controller (MVC) pattern