2007年4月3日 星期二

經典c程式100例 41-50

【程式41】
題目:學習static定義靜態變數的用法   
1.程式分析:
2.程式源代碼:

#include "stdio.h"
varfunc()
{
int var=0;
static int static_var=0;
printf("\40:var equal %d \n",var);
printf("\40:static var equal %d \n",static_var);
printf("\n");
var++;
static_var++;
}
void main()
{int i;
 for(i=0;i < 3;i++)
  varfunc();
}

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【程式42】
題目:學習使用auto定義變數的用法
1.程式分析:      
2.程式源代碼:

#include "stdio.h"
main()
{int i,num;
num=2;
 for (i=0;i < 3;i++)
 { printf("\40: The num equal %d \n",num);
  num++;
  {
  auto int num=1;
  printf("\40: The internal block num equal %d \n",num);
  num++;
  }
 }
}

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【程式43】
題目:學習使用static的另一用法。   
1.程式分析:
2.程式源代碼:

#include "stdio.h"
main()
{
int i,num;
num=2;
for(i=0;i<3;i++)
{
printf("\40: The num equal %d \n",num);
num++;
{
static int num=1;
printf("\40:The internal block num equal %d\n",num);
num++;
}
}
}

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【程式44】
題目:學習使用external的用法。
1.程式分析:
2.程式源代碼:

#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);
}

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【程式45】
題目:學習使用register定義變數的方法。
1.程式分析:
2.程式源代碼:

void main()
{
register int i;
int tmp=0;
for(i=1;i<=100;i++)
tmp+=i;
printf("The sum is %d\n",tmp);
}

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【程式46】
題目:宏#define命令練習(1)   
1.程式分析:
2.程式源代碼:

#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("\40:Please 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;
}
}

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【程式47】
題目:宏#define命令練習(2)
1.程式分析:            
2.程式源代碼:

#include "stdio.h"
#define exchange(a,b) { \ /*巨集定義中允許包含兩道衣裳命令的情形,此時必須在最右邊加上"\"*/
            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);
}

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【程式48】
題目:宏#define命令練習(3)   
1.程式分析:
2.程式源代碼:

#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");
}

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【程式49】
題目:#if #ifdef和#ifndef的綜合應用。
1. 程式分析:
2.程式源代碼:

#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
}

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【程式50】
題目:#include 的應用練習   
1.程式分析:
2.程式源代碼:

test.h 文件如下:
#define LAG >
#define SMA <
#define EQ ==
#include "test.h" /*一個新檔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");
}

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