FAQ 5.12 How does OO help produce flexible and extensible software?

By minimizing the ripple effect of enhancements.

Even in well-designed structured systems, enhancements often require modifications to significant portions of existing design and code. OO achieves flexibility by (1) allowing the past to make use of the future, and (2) designing for comprehensibility.

The past can make use of the future when old user code (the past) can reliably and predictably call new server code (the future) without any modifications to the old user code. Inheritance, polymorphism, and dynamic binding are used to achieve this lofty goal.

Comprehensibility allows software to be understood not only by the original development team, but also by the team making the enhancements. Abstraction and specification are used to achieve this lofty goal.

This approach can be contrasted with software developed using the traditional, structured approach, where enhancements or modifications often lead to a seemingly endless cycle of random modifications (a.k.a. hacks) until the system appears to work.