说明：  本次程序设计的主要目的是创建一个银行帐户的继承层次，表示银行的所有客户。Account基类用于实现账户余额初始化以及向账户中余额加钱、减少账户中余额、获取当前账户余额的基本功能；派生类储蓄账户SavingAccount类可计算利息并将利息加到账户余额中；派生类支票帐户CheckingAccount类实现每笔交易收取一定交易费用；均可处理账户余额不足的出错情况。
(The main purpose of this program is designed to create a bank account of the inheritance hierarchy, means that all bank customers. Account account balance used to implement the base class initialization and add money to the account balance, reducing the account balance, the basic functions of the current account balance of acquisition derived class to calculate interest on savings accounts and interest SavingAccount class added to the account balance derived class CheckingAccount class implements a checking account charges a transaction fee for each transaction insufficient account balance can handle error conditions.)