#include<stdio.h>
int main()
 {  void copy_string(char *from,char *to);
    char *a="I am a teacher.";  char *b="You are a student.";
    printf("string a=%s\nstring b=%s\n",a,b);  printf("\ncopy string a to string b:\n");   
    copy_string(a,b);  printf("string a=%s\nstring b=%s\n",a,b);  return 0; }  
void copy_string(char *from,char *to)
{  for(;*from!='\0';from++,to++)   *to=*from;  *to='\0'; }
弟兄们看看这是哪错了？