If you spent a few years programming in C, you're probably much more confident about your knowledge of the language than if you spent as much time working with C++ or java.

Both the C language and its standard library are quite close to the smallest they could be.

The current most used version of the language, c99, brought a bunch of new features, many of which are completely unknown to most C programmers (Older specifications obviously also have some dark corners).

Here are the ones I know about.