void print_by_code () {
	int i,j;
	struct phonebook *temp,**entry2;
	entry2=(struct phonebook **)malloc(phone_size*sizeof(struct phonebook*));
	if (entry2==NULL) {
	    printf("MEMORY ERROR!\n");
	}
	for (i=0; i<phone_size; i++) {
	    entry2[i]=entry[i];
    }      
  	for (i=0; i<phone_size; i++) {
		for(j=i+1; j<phone_size; j++) {
			if ((*entry2[i]->code)<(*entry2[j]->code)) {
			}
			else {
				temp=*entry2[i];
				*entry2[i]=*entry2[j];
				*entry2[j]=temp;
			}
		}
	} 
	printf("code username region time\n");
	for (i=0; i<phone_size; i++) {
		printf("%d %s %s %d\n",entry2[i]->code,entry2[i]->username,entry2[i]->region,entry2[i]->time);
	}
	printf("\n");
}