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程序源代码：

#include "stdio.h"

int a,b,c;

void add()

{ int a;

a=3;

c=a+b;

}

void main()

{ a=b=4;

add();

printf("The value of c is equal to %d\n",c);

}

题目：学习使用register定义变量的方法。

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程序源代码：

void main()

{

register int i;

int tmp=0;

for(i=1;i<=100;i++)

tmp+=i;

printf("The sum is %d\n",tmp);

}

题目：宏#define命令练习(1)

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程序源代码：

#include "stdio.h"

#define TRUE 1

#define FALSE 0

#define SQ(x) (x)*(x)

void main()

{

int num;

int again=1;

printf("\40: Program will stop if input value less than 50.\n");

while(again)

{

printf("\40lease input number==>");

scanf("%d",&num);

printf("\40:The square for this number is %d \n",SQ(num));

if(num>=50)

　again=TRUE;

else

　again=FALSE;

}

}

题目：宏#define命令练习(2)

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程序源代码：

#include "stdio.h"

#define exchange(a,b)

{ \ /*宏定义中允许包含两道衣裳命令的情形，此时必须在最右边加上"\"*/

　int t;\

　t=a;\

　a=b;\

　b=t;\

}

void main(void)

{

int x=10;

int y=20;

printf("x=%d; y=%d\n",x,y);

exchange(x,y);

printf("x=%d; y=%d\n",x,y);

}

题目：宏#define命令练习(3)

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程序源代码：

#define LAG >

#define SMA <

#define EQ ==

#include "stdio.h"

void main()

{ int i=10;

int j=20;

if(i LAG j)

printf("\40: %d larger than %d \n",i,j);

else if(i EQ j)

printf("\40: %d equal to %d \n",i,j);

else if(i SMA j)

printf("\40:%d smaller than %d \n",i,j);

else

printf("\40: No such value.\n");

}

题目：#if #ifdef和#ifndef的综合应用。

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程序源代码：

#include "stdio.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

}

题目：#include 的应用练习

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程序源代码：

test.h 文件如下：

#define LAG >

#define SMA <

#define EQ ==

#include "test.h" /*一个新文件50.c，包含test.h*/

#include "stdio.h"

void main()

{ int i=10;

int j=20;

if(i LAG j)

printf("\40: %d larger than %d \n",i,j);

else if(i EQ j)

printf("\40: %d equal to %d \n",i,j);

else if(i SMA j)

printf("\40:%d smaller than %d \n",i,j);

else

printf("\40: No such value.\n");

}

题目：学习使用按位与 & 。　　　

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程序分析：0&0=0; 0&1=0; 1&0=0; 1&1=1

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程序源代码：

#include "stdio.h"

main()

{

int a,b;

a=077;

b=a&3;

printf("\40: The a & b(decimal) is %d \n",b);

b&=7;

printf("\40: The a & b(decimal) is %d \n",b);

}

题目：学习使用按位或 | 。