示例描述：本章实现了电子通讯录系统，功能包括用户注册、用户登录、修改密码、添加好友、添加好友联系方式、修改好友联系方式、删除好友联系方式等。-Sample Descr iption: This chapter implements electronic address book system, features include user registration, user login, change passwords, add friends, add friends contact fri