???????????????????????????

????2. ??????????????????
???????9??????????????????????????????????????????????????????????????????????????????Э??????Щ?????????????????????12.4????????????????account????????????????????????????empty acct??setup acct????????????????????????????????working acct???У????withdraw??close???account??????nonworking acct????dead acct???????

?12.4 account?????????

???????????????????????????????????????????????????account?????????????????????????
????????????#s1:open·setupAccnt·deposit(initial)·withdraw(final)·close
???????????????г?????????12.4.1???????С???????????????С?????м????????????У?????ó???????????????
????????????#s2:open·setupAccnt·deposit(initial)·deposit·balance·credit·withdraw(final)·close
????????????#s3:open·setupAccnt·deposit(initial)·deposit·withdraw·accntInfo·withdraw(final)·close
????????????????????????????????????????????????????????????????????????????????Э????????￡????????????????????????????