SOLID principles are the design principles that enable us to manage most of the software design problems. Robert C. Martin compiled these principles in the 1990s. These principles provide us with ways to move from tightly coupled code and little encapsulation to the desired results of loosely coupled and encapsulated real needs of a business properly. SOLID is an acronym of the following. S: Single Responsibility Principle (SRP) O: Open closed Principle (OCP) L: Liskov substitution Principle (LSP) I: Interface Segregation Principle (ISP) D: Dependency Inversion Principle (DIP)