In the C and C++ programming languages, what is the difference between using angle brackets and using quotes in an
include statement, as follows?
In practice, the difference is in the location where the preprocessor searches for the included file.
#include <filename> the preprocessor searches in an implementation dependent manner, normally in search directories pre-designated by the compiler/IDE. This method is normally used to include standard library header files.
#include "filename" the preprocessor searches first in the same directory as the file containing the directive, and then follows the search path used for the
#include <filename> form. This method is normally used to include programmer-defined header files.
A more complete description is available in the GCC documentation on search paths.