c++ - <iostream> vs. <iostream.h> vs. "iostream.h"

Question

When including a header file in C++, what's the difference between...

1) including the .h versus not including the .h when wrapping it in < > signs?

#include <iostream> vs. #include <iostream.h>

2) wrapping the header name in double quotes versus wrapping it in < > signs?

#include <iostream.h> vs. #include "iostream.h"

Thanks in advance!

Answer 1

In short:

iostream.h is deprecated—it is the original Stroustrup version. iostream is the version from the standards committee. Generally, compilers point them both to the same thing, but some older compilers won't have the older one. In some odd cases, they will both exist and be different (to support legacy code) and you then must be specific.

"" versus <> simply means check the local directories for the header before going to the library (in most compilers).