#include "stdio.h"
main()
{
  int letters,digits,others;
  char c;
  c=getchar();
  letters=0;digits=0;others=0;
  while(c!='Y'||c!='y'||c!='N'||c!='n')
      if(c>='A'&&c<='Z'||c>='a'&&c<='z')
      letters++;
      else if(c>='0' && c<='9')
      digits++;
      else
      others++;
      if(c=='Y'||c=='y')
      {printf("lettes:%d",letters);
      printf("digits:%d",digits); }
      else
      printf("others:%d",others);
}

麻烦你在提问的时候 说说自己（代码）想干什么

重写吧，从hello,world开始

#include "stdio.h"
void main()
{
  int letters,digits,others;
  char c;
//  c=getchar();
  letters=0;digits=0;others=0;

 // while(c!='Y'||c!='y'||c!='N'||c!='n')
  while(c=getchar())
  {
      getchar();
      if(c>='A'&&c<='Z'||c>='a'&&c<='z')
           letters++;
      else 
     {
              if(c>='0' && c<='9')
               digits++;
              else 
               others++;
      }
  
      if(c=='Y'||c=='y')
          break;
  }
      printf("lettes:%d",letters);
      printf("digits:%d",digits); 

 //     else
      printf("others:%d",others);
      return ;
}