Where are standard system directories?

[ali hagigat <hagigatali@xxxxxxxxx>]

I have copied part of Linux GCC man pages:
-----------------------------------------------------------------------------------------
-nostdinc
           Do not search the standard system directories for header
files.  Only the
           directories you have specified with -I options (and the
directory of the
           current file, if appropriate) are searched.
-----------------------------------------------------------------------------------------
What are the standard system directories for header files exactly? and
What are the standard system directories for libraries?