#include<stdio.h>
void main()
{
    char str[]={"abcdefghij"},*p1,*p2,ch;
    p1=p2=str;
    while(*p2!='\0')
        p2++;
      p2--;              why??
       while(p1<p2)
       {
           ch=*p1;
           *p1=*p2;
           *p2=ch;
           p1++;
           p2--;    why??
       }
       puts(str);
}