help on the following:

1.) what are the different types of OS Files, particularly, the extention names?

2.) what are the Programming Languages that can be used? can Machine Language be used on those files?

3.) can anyone help me on those languages? I'm afraid I'm not knowledgeable on those...^^

I'm self studying on virus creation and prevention, hehehe.. you see guys I'm planning my thesis proposal as early as now... any help will be appreciated, thanks!