In SOLID, what does the O represent?

In SOLID, what does the O represent?

• A. Open for modification
• B. Open and Closed Principle
• C. Obvious Compliance
• D. Open-Closed Principle

Answer: (D)

The O in SOLID is the Open-Closed Principle. It means software entities should be open to extension but closed to modification. In practice, you design code so you can add new features by adding new code rather than changing existing code, which helps keep things stable and reduces the risk of introducing bugs elsewhere. A helpful way to see this is through abstractions: define an interface or abstract class that captures the behavior, and implement concrete classes that fulfill that contract. When you need new behavior, you add a new class that implements the interface rather than touching the existing implementations. For example, a Shape interface with a draw method lets you add new shapes by creating new classes like Circle or Triangle that implement Shape, while existing shapes stay unchanged and continue to work through the same interface. The other options don’t fit the standard naming or meaning. Open for modification would contradict the principle, Open-Closed Principle is the correct and conventional term, and Obvious Compliance isn't related to SOLID.

The O in SOLID is the Open-Closed Principle. It means software entities should be open to extension but closed to modification. In practice, you design code so you can add new features by adding new code rather than changing existing code, which helps keep things stable and reduces the risk of introducing bugs elsewhere.

A helpful way to see this is through abstractions: define an interface or abstract class that captures the behavior, and implement concrete classes that fulfill that contract. When you need new behavior, you add a new class that implements the interface rather than touching the existing implementations. For example, a Shape interface with a draw method lets you add new shapes by creating new classes like Circle or Triangle that implement Shape, while existing shapes stay unchanged and continue to work through the same interface.

The other options don’t fit the standard naming or meaning. Open for modification would contradict the principle, Open-Closed Principle is the correct and conventional term, and Obvious Compliance isn't related to SOLID.