What is the main goal and application of SOLID principles in software development?

The SOLID principles are a set of recommendations for software development aimed at creating flexible, extendable, and maintainable systems. The main goal of SOLID is to improve code quality and ease its support.

Briefly about each principle:

• S (Single Responsibility Principle): a class should have only one reason to change.
• O (Open/Closed Principle): software entities should be open for extension but closed for modification.
• L (Liskov Substitution Principle): objects of subclasses should be interchangeable with objects of the base class.
• I (Interface Segregation Principle): it's better to have several specific interfaces than one general.
• D (Dependency Inversion Principle): high-level modules should not depend on low-level modules; both should depend on abstractions.

Applying SOLID helps create code that is easier to test, extend, and support, which is especially important in large and long-term projects.