Design Games

I have to which operating systems a best for a games design company for programing, tesing & deasigning?
So they have to design them using, say for example Auto CAD.
They need to program them and then they need to test them.
Do you have any examples of which operating systems games design companies would use?
Thanks!
www.google.com ( gaming design programs)
barnes and noble in the computer book section –so about 7 yesterday
Game Design Lessons: From Seconds to Hours of Gameplay