实验2

#include<stdio.h>
#include<stdlib.h>

int main()
{
    int  c=1, n, sum=1, i;
    printf("请输入一个数字n:\n");
    scanf("%d",&n);
    for(i=0; i<n; i++)
    {
        c=c*2; 
        sum=sum+c;
              
}
    printf("sum的值为；%d\n", sum);
    return 0;
}

//格式化输入、输出函数的简单运用
#include <stdio.h>
int main()
{
int num;
scanf("%d",& num);
printf("2049%04d\n",num);

scanf("%d",&num);
printf("2049%04d\n", num);

scanf("%d",&num);
printf("2049%04d\n", num);

return 0;
 } 

//格式化输入输出函数，及各种格式控制符的使用 

#include <stdio.h>
int main()
{
int x=1234;
float f=123.456;
double m=123.456;
char ch='a';
char a[]="hello, world!";
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);
printf("%f, %8f, %8.1f, %0.2f, %. 2e\n", f, f, f, f, f);
printf("%lf\n", m);
printf("%3c\n", ch); 
printf("%s\n%10.5\n%2.5s\n%.3s\n", a, a, a, a, a);

return 0;
 } 

#include <stdio.h>
int main()
{


    double x, y;
    char c1, c2, c3;
    int a1, a2, a3;

    scanf("%d%d%d",&a1, &a2, &a3);
    printf("%d, %d, %d\n", a1, a2,a3);
    scanf("%c%c%c", &c1, &c2, &c3);
    printf("%c%c%c\n", c1, c2, c3);
    scanf("%lf, %lf", &x, &y);
printf("%lf, %lf", x, y); 

return 0;
 } 

#include <stdio.h>
int main() {
    char ans1, ans2;
    
    printf("复习了没? (输入y或Y表示复习了，输入n或N表示没复习) :  ");
    ans1 = getchar();  
            
    getchar(); 
        
    printf("\n动手敲代码了没? (输入y或Y表示敲了，输入n或N表示木有敲) :  ");
    ans2 = getchar();
            
    if(ans1=='Y'&&(ans2=='y'||ans2=='Y')||ans1=='y'&&(ans2=='y'||ans2=='Y')) 
        printf("\n罗马不是一天建成的:)\n");
    else
        printf("\n罗马不是一天毁灭的。。。\n");    
        
        return 0;
    }

//判断字符类型 
# include <stdio.h>
int main()
{ 
char x;
x=getchar();


if(x>='0'&&x<='9')
  printf("%c是数字字符\n", x);
else if(x>='a'&&x<='z'||x>='A'&&x<='Z')
  printf("%c是大写或小写字母\n", x);
else 
  printf("%c是其他字符\n",x); 
  
  return 0; 
 
 }