第二次实验

#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;
}

#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%15s\n%10.5s\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("%f,%f\n",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(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;
} 

#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是英文字母\n", x);
    else
    printf("%c是其它字符\n", x);
    
    return 0;
} 

#include<stdio.h>
#include<math.h>
int main() 
{
    int n, s;
    scanf("%d",&n);
    s = (1-pow(2,n))/(1-2);
    printf("%d",s);
    return 0;

}