Include Header not found in the project: Altera-SoCFPGA-HardwareLib-GPIO-CV-GNU

Hello,

I downloaded this example : Altera-SoCFPGA-HardwareLib-GPIO-CV-GNU.

When I build the project the compiler cannot find the following headers:

#include "alt_generalpurpose_io.h"

#include "alt_interrupt.h"

#include "alt_globaltmr.h"

#include "alt_clock_manager.h"

Can I download these files?

What path is it necessary to indicate in the project?

Thanks for your help

Jerome