"I want to learn security and game designing."
Security: What do you mean by this? Do you want to learn how to write Firewall rules in a router to prevent people from accessing a network, creating programs like Fortress that prevent end users from preforming X functions??
Gaming: Before getting into the nitty gritty of this, you need to have pretty good math skills (Linear Algebra, Calculus, etc) for game design because almost every aspect of a video game relies on a mathmatical computation.
In so far as Gaming is concerned, you could go a few different routes. Elitests will say that you need to use C++ to develop video games and while it is the most widely used language for this type of thing Microsoft has released a Game Development Framework (XNA) that allows you to develop video games using C# that are playable on Windows and on the XBOX 360. (Wrox released a book entirely on this subject called: Professional XNA Game Programming: For Xbox 360 and Windows personally I have read that book and it is a pretty good book to get you going and it can also be found on
http://wrox.books24x7.com/ )
hth.
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Read this if you want to know how to get a correct reply for your question:
http://www.catb.org/~esr/faqs/smart-questions.html
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.: Wrox Technical Editor :.
Wrox Books 24 x 7
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