==============================================================

　　【程序49】

　　題目：#if #ifdef和#ifndef的綜合應用。

　　1. 程序分析：

　　2.程序源代碼：

　　#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();

　　}