What is  a great software?
A great software is a software that:
• Satisfies customers’ needs and demands i.e does what it is expected to do correctly.
• Is well-designed and well-coded and
• Is easy to maintain, reuse and extend.
A software that works correctly is not enough, it should be well designed and coded so that it can be easy to maintain, reuse (eliminates code duplication) and extend(add new features with little or no change). Such software should be open to extension but closed to modification and designed using proven Design Patterns and Object-Oriented Designs.
NB: Make it work then make it better, focus on meeting the customer’s demands first, once your software works look for any duplicate code and eliminate it using OOP techniques. Now, you have a working OOP software that does what the customer wants, it’s time to apply pattern designs and principles to ensure that you code is ready for reuse, extension and maintainance in the future.