What is meant by just C is the C programming Language.
Here is a small C Primer that may be helpful, the document needs many more parts, so use with care.
Auditing C code
Auditing C code gets done by people who look for bugs. When a program crashes someone may find a bug, writes a patch or lets someone else write a patch after giving up enough data about the bug. Visual auditing can also be done. It's best to do auditing in some structured way or form, otherwise it's just searching for a needle in a haystack.