What should I learn to make a complex gaming app? from where should I start?

What operating system is a smartphone most likely to use? 1.bsd 2.mac os x 3.symbian 4.linux

An atom's diameter is about 0.1 nanometer (1×10-9m), and a human hair is about 1×10-3m. how many times greater is a human hair than an atom's diameter? sorry pushed wronf button but this is math

David is in week 3 of his current ashford course and has a paper due by monday night at midnight. he has finished everything but the concluding paragraph. as he boots up his computer to work on it, he sees a flash across the screen and then the screen goes black. he begins to panic as he tries desperately to turn the laptop back on. david should have saved his work on what kind of portable device?