#include <stdio.h>
 int main() 
{ 
printf(" O   O \n"); 
printf("<H> <H>\n"); 
printf("I I I I\n"); 
return 0; 
}

#include <stdio.h>
 int main() 
 {
  float x, y; 
   float r1, r2, r3, r4;
     x = 1; y = 2;
	  r1 = x + y; 
	  r2 = x - y; 
	  r3 = x * y; 
	  r4 = x / y; 
	   printf("r1 = %f\n", r1);
	   printf("r2 = %f\n", r2); 
	   printf("r3 = %f\n", r3); 
	    printf("r4 = %f\n", r4); 
		 return 0; 
		 }
	 

　　

#include <stdio.h>
 int main() 
{ 
int n, r1, r2, r3, r4;
 n = 100;
r1 = n*(n+1)/2; 
r2 = (n+1)*n/2;
 r3 = n/2*(n+1); 
r4 = (n+1)/2*n; 
printf("n = %d\n", n);
 printf("r1 = %d\n", r1);
 printf("r2 = %d\n", r2);
 printf("r3 = %d\n", r3); 
printf("r4 = %d\n", r4); 
return 0; 
}

#include <stdio.h>
 int main()
 {
 int answer;
 char words[5000]; 
printf("网课学习让一些人欢喜一些人忧.\n");
 printf("1. 作为一个宅，社恐，觉得这样很好. 有网络，自主学习，很ok.\n");
 printf("2. 不喜，不喜，很不喜. 眼睛快瞎了. 脑壳有点卡...\n"); 
printf("3. 中间派. 不知道. 说不清.\n");
 printf("4. 其它...\n"); 
 printf("你的选择: ");
 scanf("%d", &answer); 
if(answer == 4)
 {
 printf("请补充说明你的想法: \n");
getchar(); 
 gets(words); 
}
printf("\n"); 
 printf("当遇到问题时, 你会选择:\n");
 printf("1. 遇到问题, 就解决问题。不懂的，搜索式学习，逐个攻破.\n");
 printf("2. 遇到问题, 不高兴。然后,...,没有了.\n"); 
printf("3. 其它...\n"); 
printf("你的选择: "); 
scanf("%d", &answer);
 if(answer == 1) 
printf(":)\n");
 else if(answer == 2)
 printf("这样不能解决问题啊...我们选择1好不好:)\n");
 else if(answer == 3) 
{ 
printf("请补充说明你的想法: \n"); 
getchar(); 
gets(words);  
}
return 0; 
}