The preprocessor #include directive appears in two flavors:
#include < vector > // angular brackets
and
#include "myclass.h" // quotes
The two are not interchangeable. The angular-bracket version applies to standard header files.
The quoted version applies to all the rest: user’s header files or implementation dependent ones (like “winsock.h”). The quoted version may contain the full path name. Otherwise, the current directory is assumed.