What is the difference between and “stdio.h”? [duplicate]

Answer 1

#include <something.h> is meant for system headers, while #include "something.h" is for headers of your own program. System headers are searched for in usual system directories (and those included with -I argument), which your headers are searched for in current directory and then the same locations as system headers.

see http://gcc.gnu.org/onlinedocs/gcc-2.95.3/cpp_1.html#SEC6

Answer 2

<stdio.h> refers to a header (not a header file)
"stdio.h" refers to a source file.

Headers need not exist phisically in the implementation; the way they are identified is implementation-defined (usually the headers are files on specific directories)

When the directive uses ", the source file is searched in an implementation-defined manner and, if not found, the directive is reprocessed as if it was written with < and > in the first place.

Answer 3

Normally standard header files are enclosed by < > and other user specific files are specifed with " .

Answer 4

You use #include when you want to say: "look for a file with this name in the system's include directory". You use #include "doublequoted" when you want to say: "look for a file with this name in my own application's include directory; however, if it can't be found, look in the system's include directory".

Answer 5

The difference is that header files made by the developer are enclosed by "". Header files that are already in the system are enclosed with <>. Even the <> headers need the -I directive if the directories that are placed are not in the search path of the compiler.

Bottom line: Your headers with "", system headers with <>

Answer 6

The <> tell the compiler to look for the file in the libraries' headers and "" tell it to look around among your application's headers.

As for why both of them works for you, maybe your compiler also looks for the filename in the library headers in case it didn't find one among yours.