#include <stdio.h>
void fun(char p1[], char p2[])
{
  int i,j;
  for(i=0;p1[i]!='\0';i++)  ;  
      for(j=0;p2[j]!='\0';j++)
          p1[i++]=p2[j];
   p1[i]='\0';
}

main()
{    char s1[80], s2[40] ;void NONO ();

     printf("Enter s1 and s2:\n") ;
     scanf("%s%s", s1, s2) ;
     printf("s1=%s\n", s1) ;
     printf("s2=%s\n", s2) ;
     printf("Invoke fun(s1,s2):\n") ;
     fun(s1, s2) ;
     printf("After invoking:\n") ;
     printf("%s\n", s1) ;
     NONO() ;
}

i和j是怎么变化的特别是p1[i＋＋]=p2[j++]