A banking system has many customers. Each customer may have a savings account, a cheque account, and an investment account, one account of each type. The bank offers access to cheque and savings accounts through an interactive menu like that seen in an automatic teller machine (ATM); an investment account cannot be accessed through the ATM. Savings and investment accounts accrue daily interest, paid on the current balance; cheque accounts do not accrue interest.
A positive amount may be deposited in an account or withdrawn from an account. A withdrawal from a savings account decrements the balance by that amount; there are no charges or penalties for a savings account. A successful withdrawal from a cheque account costs 50 cents. An unsuccessful withdrawal from a cheque account costs $5. The balance of an account cannot be negative.
A savings account gets daily interest; the interest rate is 4.5% a year. A cheque account gets no interest. An investment account is created with an initial balance of at least $1000, and accrues daily interest for a period of 3, 6, or 12 months. A 3-month investment account has an annual interest rate of 5.5%, a 6-month account has a 6.0% rate, and a 12-month account 6.5%. When the account matures at the end of the period, the total amount is transferred into the customer's cheque account.
The bank system runs for an extended period. At the start of each day, a bank teller creates new customers, and new accounts for existing customers. Each customer has a unique integer key; successive integers are used for each new customer. Customers and accounts are never deleted from the bank. The ATM then runs all day, handling multiple customers. To use the ATM, a customer enters their unique key (this simulates putting a card into the ATM) and their password, chooses an account, then chooses commands from the menu. Menu commands are read and executed until the customer finishes; the ATM then waits for the next customer. A special key of 666 exits the ATM system for the day. Interest is then added to all savings and investment accounts. Entry of the special key value of 999 into the ATM shuts down the whole system. The bank data is stored to file when the system shuts down, and is retrieved from file when the system starts up again.
A customer is allowed three attempts to login to the ATM by entering a valid password. If no correct password is entered after three attempts, then the ATM system rejects the login attempt and asks for a new customer identifier. If the password is correct, then the customer is shown a menu of account choices, and the system reads and executes the choices. Any number of transactions may be made; processing on the account continues until the customer chooses to exit that account. Multiple accounts may be chosen and used within a single ATM session.
The ATM menu choices (upper or lower case) are
| D Deposit |
| W Withdraw up to the total amount in the account |
| B Show the balance |
| Q Quit the system |
| H Help: Show themenu choices |
The first inheritance chart shows the inheritance for a storable, keyed
list, and for an element of that list, a customer.
The second inheritance chart shows the inheritance structure of the bank
accounts.
The first client chart shows the overall structure of the system that uses
a list of customers.
The second part of the client chart shows the use within a customer.
The first set of three diagrams shows the overall structure of the banking system.
The next set of five diagrams shows the customer subsystem.
The next set of four charts shows the account container class, and the non-ATM account classes.
The final set of four diagrams shows the ATM account classes.
The Eiffel code for the BANK system is shown on the following pages. The classes are listed in client order, and within this in inheritance order. The client and inheritance orders are shown below, taken from the client and inheritance charts. A total listing order is then given.
Client order
| BANK | TELLER | KEY_LIST | CUSTOMER | PASSWORD | |
| ACCOUNTS | SAVINGS | ||||
| CHEQUE | |||||
| INVEST | |||||
| ATM | KEY_LIST | CUSTOMER | PASSWORD | ||
| ACCOUNTS | SAVINGS | ||||
| CHEQUE | |||||
| INVEST |
Inheritance order
| KEYED | CUSTOMER | |||
| PERSON | ||||
| ACCOUNT | INTEREST | INVEST | ||
| ACCOUNT | MENU | INTERACCT | INTEREST | SAVINGS |
| ACCOUNT | MENU | INTERACCT | CHEQUE |
Listing order
| BANK |
| TELLER |
| ATM |
| KEY_LIST |
| KEYED |
| PERSON |
| CUSTOMER |
| PASSWORD |
| ACCOUNTS |
| ACCOUNT |
| INTEREST |
| INVEST |
| MENU |
| INTERACCT |
| SAVINGS |
| CHEQUE |
class BANK
inherit
STORABLE
creation
make
feature {NONE}
file_name: STRING
is "patrons.dat"
patrons: KEY_LIST[CUSTOMER]
teller: TELLER
atm: ATM
make is
-- make or retrieve the list of customers
-- make the ATM and TELLER, pass the customer list
-- run the ATM and teller until system shuts down
do
retrieve
!!teller.make (patrons)
!!atm.make (patrons)
run
--
store
io.putstring ("%N%NExit banking system%N")
end -- make
retrieve is
-- make or retrieve the list of customers
local file: RAW_FILE
do
!!file.make (file_name)
if file.exists then
file.open_read
patrons ?= retrieved (file)
file.close
show_retrieved
end
if
patrons = Void then !!patrons.make end
end -- retrieve
show_retrieved is
-- show the number of customers retrieved
do
io.putstring ("%N%T**** ")
io.putint (patrons.count)
io.putstring (" records read from file ****%N")
end -- show_retrieved
run is
-- each day, run the teller then the atm subsystems
-- at the end of a day, add interest and check investments
do
from
until atm.system_finished
loop
teller.run
atm.run
end_day
end
end -- run
end_day is
-- add interest for every customer
-- add a day to the investment counter
do
from
patrons.start
until
patrons.after
loop
patrons.item.accounts.end_day
patrons.forth
end
end -- end_day
store is
-- store the list of customers
local file: RAW_FILE
do
!!file.make (file_name)
file.open_write
patrons.basic_store (file)
file.close
end -- store
end -- class BANK
class TELLER
creation {BANK}
make
feature {NONE}
patrons: KEY_LIST[CUSTOMER]
feature {BANK}
make (customers: KEY_LIST[CUSTOMER])
is
-- set the patrons to the list of customers
do patrons := customers end -- make
run is
-- add interest to all accounts
-- create new customers
-- create new accounts for existing customers
do
show_header
new_customers
new_accounts
end -- run
feature {NONE}
show_header is
-- show the teller a nice message
do
io.putstring ("%N")
io.putstring ("%N**************************************")
io.putstring ("%N* Add new customers and new accounts *")
io.putstring ("%N**************************************")
end
new_customers is
-- add any new customers with their initial accounts
local patron: CUSTOMER
do
from ask_for_more_customers
until
no_more
loop
!!patron.make (patrons.count + 1)
patron.add_accounts
patrons.extend (patron)
ask_for_more_customers
end
end -- new_customers
ask_for_more_customers
is
-- prompt the user for more customers, read reply
&nb