gistfile1.c

#include <stdio.h>


#if defined __unix__
#define os 1
#elif defined _WIN32
#define os 2
#endif

int main()
{
	if(os == 1)
	{
		printf("Unix\n");
	}
	else if(os == 2)
	{
		printf("Windows\n");
	}

	return 0;

}