Oh! That's simple. You no need to
use the #define, #ifndef & #endif set of directives. Instead of that you should just use #pragma once pre-processor directive. And it will
take care of every thing. Below is sample by making small change in the extendedmath.h
#pragma
once
#include
"SimpleMath.h"
int
Add_three_numbers(int, int, int);
int
Add_three_numbers(int a, int b, int c)
{
return
( Add_Numbers(a, b) * c );
}