This may be a ridiculous question, but it seems like a reasonable one to me... I often open up source files and see various system header files included and wonder what each of them are. I know what the likes of `stdio.h` and `sys\types.h` are for, but there are others that I'm not too sure about. Is there someplace that gives a list of standard header files and a description of their purpose (and details given per OS, language standard)? Maybe this list would also include definitions included in said header files, macros, etc. Something organised by topic would be helpful, too.