Are you need an OO concept to develop Client Application?
Sometimes a good student know how to code, but hard to tell in OO concept. In the real world software development OO become ubiquitous, sometime we do an OO automatically. Just like an API in many .NET Classes. Sometimes we implement interface because we need get existing functionality form legacy namespace. In the end the counter is a working application. A working and good application will implement OO pervasively, it will blend into your code, it will integrate with your software maintainability. The Good OO will survive your application.
However, OO is not enough. Just like what James Bond said “The (OO) World is not enough”, we see a lot of client application is created by adopting several architecture style from layer architecture, oo, and component based model architecture. It’s more than OO! it’s about working software, a software that give benefit to others. If I am a lecturer, I shall give an “A” for every student who can submit their client application to the real world. Because, the real world software is more than just OO!