I was wondering what is out there concerning C to look at in the future.

I know there is socket programming (what I presume is networking) and AI programming but what more is there and when is it used for example? Looking at AI programming I would presume it is used mostly in games...

Next to that is it possible to code a GUI in C or do I need to learn C++ or a different language next to C if I would like to code one?

Thanks in advance.