[Dev-C++] #pragma directive

[Vlada D. <dj...@im...>]

In the book I'm currently reading, #pragma once directive is used a lot to
make sure that no header files are included more than once. When I compile
the program, I get warnings " #pragma once is obsolete". The book is
published this year, so I don't think it's too old.
I found another way for doing the same thing in Bruce Eckel's "Thinking in
C++", like this:

#ifndef FLAG
#define FLAG
#includefoo.h  ///include needed headers
-------------
#endif

Which way is better in your opinion? Or do you recommend something else?
Thanks.
------------
Vlada