重点是复制过程中会把结束\0也会复制到目标，实例如下

#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
  char arr1[] = "hello";
  char arr2[20] = "***************";
  strcpy(arr2, arr1);
  printf("%s\n", arr2);
 return 0;
}