Now, the nice thing here is that you can write code to only deal with Animals. Then someone out there can go and code a Human Animal, for instance, and all your code will work nicely with this new case without any modification. Isn't that cool? 

  

 Ok, sure, it is a contrived example. Which is actually a bit of a problem. You see, given a very good design, object oriented programming is, well, very good. Unfortunately, this design is very hard to come by. Some think it is impossible for many situations. So therein lies the real problem. It is easy to think up silly situations where object oriented programming works flawlessly. In practice, it can be very hard to apply. There are some good situations. Windowing systems come to mind: a well designed GUI can make excellent use of object oriented programming. 

  

  

 There is a lot of theory involved in ObjectOrientation. A lot of processes have been invented in attempts to make designing systems easier: people who have studied it may remember CRC cards and class diagrams. Object oriented design purists will talk about class responsibilities and communications between classes and such. 

  

 Done well, object oriented programming is great. Given a good design, doing it well is not all that hard. Getting a good design is often near impossible. 

  

 The last two points are just trying to get across the fact that some of the ideas of ObjectOrientation can be used in general programming without "going the full hog" and using all the design patterns and implementing things in a purely object oriented way. 

  

 (Feedback to SamJansen if you like)