c语言中 ifdef,c语言中的#ifdef和#ifndef

#include "stdio.h"

#include "conio.h"

#define MAX

#define MAXIMUM(x,y) (x>y)?x:y

#define MINIMUM(x,y) (x>y)?y:x

void main()

{

int a=10,b=20;

#ifdef MAX

printf("\40: The larger one is %d\n",MAXIMUM(a,b));

#else

printf("\40: The lower one is %d\n",MINIMUM(a,b));

#endif

#ifndef MIN

printf("\40: The lower one is %d\n",MINIMUM(a,b));

#else

printf("\40: The larger one is %d\n",MAXIMUM(a,b));

#endif

#undef MAX

#ifdef MAX

printf("\40: The larger one is %d\n",MAXIMUM(a,b));

#else

printf("\40: The lower one is %d\n",MINIMUM(a,b));

#endif

#define MIN

#ifndef MIN

printf("\40: The lower one is %d\n",MINIMUM(a,b));

#else

printf("\40: The larger one is %d\n",MAXIMUM(a,b));

#endif

getch();

}

原文：http://www.cnblogs.com/zhaoheng/p/4322214.html