实验2

2.1-------------------------------------------------------------------------
#include<stdio.h>
#define EOF -1
int main()
{
    int num;
    
    
    while(scanf("%d",&num)!=EOF)  //不要加; 
      {
      printf("2049%04d\n",num);  //while加{} ，0即用0补齐
    }
     return 0;
 } 










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2.2-------------------------------------------------------------------------------
#include<stdio.h>
int main()
{
    int x=1234;
    float f=123.456;
    double m=123.456;
    char ch='a';
    char a[]="Hello world!";                        //[15]从第12个字符开始，后面均为\0,要加[] 
    int y=3,z=4;
    
    printf("%d%d\n",y,z);    
    printf("y=%d,z=%d\n",y,z);    
    printf("%8d,%2d\n",x,x);                         //长度小于真实长度，照常输出 
    printf("%f,%8f,%8.1f,%.2f,%.2e\n",f,f,f,f,f);      //前方的逗号仅仅就是输出时加个逗号 ,lf和f 
    printf("%lf\n",m);    
    printf("%3c\n",ch);    
    printf("%s\n%15s\n%10.5s\n%2.5s\n%.3s\n",a,a,a,a,a);    //s的.几是取几个字符   前面是共占几个长度 
    
    
    
    
    return 0;






}
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2.3------------------------------------------------------------------------------
#include<stdio.h>
int main()
{
    double x,y;
    char c1,c2,c3;
    int a1,a2,a3;
    
    scanf("%d%d%d",&a1,&a2,&a3);  //scanf前少& 
    printf("%d,%d,%d\n",a1,a2,a3);
    
    
    scanf(" %c %c %c",&c1,&c2,&c3); //%c前加空格，可抵消掉回车占的字符 
    printf("%c,%c,%c\n",c1,c2,c3);
    
    
    scanf("%lf%lf", &x,&y);//scanf读%f时，按照四个字节读，double有8字节，要用lf 
    printf("%f,%lf\n",x,y);
    
    
    
    return 0;
    
    
    
    
}
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2.4
#include<stdio.h>
int main(){
    
    char ans1,ans2;
    
    printf("Have you reviewed?(scan Y or y is yep; scan N or n is nope.):");
    
    ans1=getchar();
    getchar();               //要用enter键表示输入结束 
    
    printf("Have you scan your code by yourself?(scan Y or y is yep; scan N or n is nope.):");
    ans2=getchar();

    
    if((ans1=='Y'||ans1=='y')&&(ans2=='Y'||ans2=='y'))   //别把==打成= 
      printf("Rome is not built in one day\n");
    else
      printf("Rome is not ruined in one day\n");
      
      return 0; 
    
    
    
}
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2.5
#include<stdio.h>
#define EOF -1 
int main()
{
    char x;
    while((scanf(" %c",&x))!=EOF)
    
    {
    if(x>='0'&&x<='9')              //判断字符的大小时不必加'' 
       printf("%c是数字字符\n",x);
    else if(x>=97&&x<=122||x>=65&&x<=90)
        {
          printf("%c是英文字母\n",x);
        } 
        else 
         
         printf("%c是其它字符\n",x); 
          
    }
    
    
    return 0;
}
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2.6
#include<stdio.h>
#include<math.h>
#define EOF -1

int main(){
    
     int a1,n,s,q;
     q=2;
     a1=pow(q,0);
    
    
     while(scanf("%d",&n)!=EOF)    //不需;且需{} 
    
    {
       if(n>=1&&n<=10)
        
        {
        s=(int)(a1*(1-pow(q,n+1))/(1-q));     //n+1项 
        printf("n = %d 时, sum = %d\n",n,s);
        
        }
       else
        
        printf("i can't do it!");
    }
    return 0;
    
    
    
    
    
    
} 
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