/* Note:Your choice is C IDE */
#include "stdio.h"
const x=100;
const y=20;
void main()
{
    int i,j;
    char a;
    char b[x];
    int c;
   
    for (i=0,a=' ';i<x;i++)
    {
        b[i]=a++;
    }
   
    for (c=0,a=' ';(a!='q')&&(a!='Q');scanf("%c",&a))
    {
        switch (a)
        {
            case 'u':
            case 'U':
               c-=y-1;
               
            break;            
            case 'd':
            case 'D':
               c+=y-1;
            break;
        }
        
        if (c<0)
        {
            c=0;
        }
        else if(c>=x)
        {
            c=x-y;
        }
        
        if (a!='\n')
        {
            for(i=c,j=0; (i<c+y)&&(i<x);i++,j++)
            {
                printf("diplay  line%d",j);
                printf(":array element%d: %c\n",i,b[x]);
            }
            printf("\nCOMMAND:");
        }
    }
}   

那帮忙改一下，谢谢

是一个滚动文档，练习使用const定义常量

试了，还是不行    char b[x];  运行时有问题

你是什么编译器？