/**********************************
*功能:判断输入的成绩的等级        *
*作者:                            *
*时间:2014\03\27                  *
*                                 *
**********************************/
#include <stdio.h>
#include <ctype.h>
int main (void)
{
    int score ; //表示输入的成绩
    printf("Please enter score:");
    scanf("%d",&score);
    while (score != '#')
    {
        if(score < 0 || score>100)
            printf("The score is fault.\n");
    else
        {
            switch(score / 10)
            {
                case 10 :
                     printf("This student's score is %d and his grade is A .\n ",score);
                     break ;
                case 9 :
                    printf("This student's score is %d and his grade is A .\n ",score);
                    break ;
                case 8 :
                    printf("This student's score is %d and his grade is B .\n ",score);
                     break ;
                case 7 :
                    printf("This student's score is %d and his grade is C .\n ",score);
                     break ;
                case 6 :
                     printf("This student's score is %d and his grade is D .\n ",score);
                     break ;
                default:
                    printf("This student's score is %d and his grade is E .\n ",score);
                    break ;
            }
            break;
        }
        
        scanf("%d",&score);
        continue ;
    }
    return 0;
}

比如我输入 -90 87 110
就要输出
The score is fault.
This student's score is 87 and his grade is B
The score is fault.



但是我这个程序执行后只有
The score is fault.
This student's score is 87 and his grade is B
就结束了
这是为什么？
哪里有问题？

条件换成：score != -1  分数不该是负数。

score是int型的。score != '#'比较时，比较的是'#'的ASCII码。不是你所想的能接收字符。

如果需要处理负数，参看下面程序：
/**********************************
*功能:判断输入的成绩的等级        *
*作者:                            *
*时间:2014\03\27                  *
*                                 *
**********************************/
#include <stdio.h>
#include <ctype.h>
int main (void)
{
    int score ; //表示输入的成绩

    printf("Please enter score:");
   

    while (scanf("%d",&score)!=EOF)  //输入ctr+z时结束
    {
        if(score < 0 || score>100)
            printf("The score is fault.\n");
    else
        {
            switch(score / 10)
            {
                case 10 :
                     printf("This student's score is %d and his grade is A .\n ",score);
                     break ;
                case 9 :
                    printf("This student's score is %d and his grade is A .\n ",score);
                    break ;
                case 8 :
                    printf("This student's score is %d and his grade is B .\n ",score);
                     break ;
                case 7 :
                    printf("This student's score is %d and his grade is C .\n ",score);
                     break ;
                case 6 :
                     printf("This student's score is %d and his grade is D .\n ",score);
                     break ;
                default:
                    printf("This student's score is %d and his grade is E .\n ",score);
                    break ;
            }
         
        }
   
    }
    return 0;
}

嗯，好！
可是为什么不能这样？
我输入：-90 87 46 101 Ctrl+z
然后程序先对前面的处理，在最后碰到了  Ctrl+z直接结束呢。
而是再次单独输入一个 Ctrl+z才能结束呢？

Ctrl+z是否单独输入都可以。

我在4楼应经说了你程序出错的原因了：
  score是int型的。score != '#'比较时，比较的是'#'的ASCII码。不是你所想的能接收字符。

另外，Ctrl+z是按组合键，即，同时按Ctrl键和z键。
“我输入：-90 87 46 101 Ctrl+z”--- 很少这样表述的。

我就是在改过的程序中进行的
就是运行后的黑色框中啊
-90 87 46 101 Ctrl+z（这个是同时的，会变成^z）
在101后不能结束
是在我再次输入Ctrl+z（这个是同时的，会变成^z）才能结束

那就打回车之后再输入比较保险一点。