# The SOLID Principles of Software Engineering

_"Don't surprise software users. Don't surprise people reading your code."_

SOLID is an acronym used for the five principles of object-oriented programming and design. These principles were first introduced by Robert C. Martin and are widely used as a guide for creating maintainable and scalable software. The SOLID principles of software engineering are as follows.

* [Single Responsibility Principle (SRP)](Single_Responsibility_Principle.md)

* [Open-Closed Principle (OCP)](Open_Closed_Principle.md)

* [Liskov Substitution Principle (LSP)](Liskov_Substitution_Principle.md)

* [Interface Segregation Principle (ISP)](Interface_Segregation_Principle.md)

* [Dependency Inversion Principle (DIP)](Dependency_Inversion_Principle.md)

There's an underlying common theme to all of these principles:

* Principle of least astonishment (POLA): 
  _"People are part of the system. The design should match the user's experience, expectations, and mental models."_

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