Their "experts" are no better than the members here. I believe there is actually certain members here that can give most, if not all of them, a run for their money.
Just because the beginners here don't know the negative effects of using the system function doesn't mean that the people who reply to messages can't accurately answer questions. This is why you don't refer people to other forums. We have more than enough experience between our members.
That being said, more than likely the reason this hasn't been answered yes is because gulzi hasn't explained what the exact issue is they don't understand.
@gulzi
Have you been trying to write any code? Have you done extra research and tried to see if a different tutorial or book explained it in a way that you understand?
Here are two links to the examples on this forum explaining both Polymorphism and File Streams.
File Streams:
http://www.cplusplus.com/doc/tutorial/files/
Polymorphism:
http://www.cplusplus.com/doc/tutorial/polymorphism/
Have a look over those two pages and consider everything that is written in them. If you're still having issues understanding what the code does, the use of these features, or anything else, feel free to post back to this thread and ask a specific question. It's hard to take a new poster serious when there is just a short post saying help me.
I look forward to hearing back from you.