And how do you know that he really knows this?
Just because he does not ask questions on the forum, but just silently makes mistakes in the code? ))
You ask for references or examples of code that he has written or open source projects to which s/he has contributed code along with links to the code s/he has written.
All that aside though, knowing how to declare of variable and what different data types are in various programming languages are is quite basic. For example, int vs float vs int64 etc. The book Danny mentioned above is a good reference to help you learn as you are going through the code. I read somewhere there was an ebook version of it, if you search for "the c programming language by brian w kernighan ebook" you may find it. At worst, having it as a reference is a good thing and you'll learn something.