程序代码：

#include <stdio.h>
#include <stdlib.h>
void main()
{
    int a,i=0;
    char p[4] = {0};
    scanf("%d",&a);

    (a<0 || a >=10000) ? printf("错误\n") : itoa(a,p,10);
    
    while(i<4 && p[i] != NULL)
    {
        printf("第%d位：%c\n",i+1,p[i]);
        i++;
    }
    
    strrev(p);
    if(i>0) printf("倒序%s\n",p);
}