SOLID principles

Solid principles are a way, a set of recommendations and principles, to build robust software. SOLID principles work for object-oriented design (OOP). Their author is Robert C. Martin and date from around 2000.

A quick overview

Character	Principle Name	Explanation
S	Single responsibility principle	Each class has just one responsibility.
O	Open/Closed principle	The functionality of a class can be extended without modifying it.
L	Liskov substitution principle	Classes must be fully substitutable by their descendants.
I	Interface segregation principle	Use small and narrowly focused interfaces.
D	Dependency inversion principle	Depend on abstractions, not on implementations.