Just in case you haven't used a documentation generator before I strongly recommend it for some situations. For example it is very helpful when you study a very big project or a hell of a code. In my field, Electronic Engineering, there are tons of engineers coding C, C+Classes, or C+Classes+SystemC with no love to the source code.
In this situation I suggest Doxygen as a documentation generator. You can use it for C++(SystemC), C, Java, Objective-C, Python, IDL (Corba and Microsoft flavors) and to some extent PHP, C#, D and ActionScript.