ATM（1）能比较迅速地找到储户的帐户，以实现存款、取款记账。 （2）能比较简单，迅速地实现插入和删除，以实现开户和销户的需要。 -(1) can be found relatively quickly depositor s account, in order to achieve deposits, withdrawals accounted for.     (2) can be relatively simple, quick insert and del