Read The C Programming Language if you want to learn C. As far as if you should learn c, I would suggest you do. Also, if you don''t specifically want to know C# then I wouldn''t think you need a transition, the only reason I''d ever think you do is an easy language for your first one and even then I learned C with no experience in other languages and my school "teaches" C++ without previous experience and everyone does fine with it.