ATM software design

loop loop Print_input_message (? Welcome - Please enter your card?) ; exit when Card_input ; end loop ; Account_number := Read_card ; Get_account_details (PIN, Account_balance, Cash_available) ; if Validate_card (PIN) then loop Print_operation_select_message ; case Get_button is when Cash_only => Dispense_cash (Cash_available, Amount_dispensed) ; when Print_balance => Print_customer_balance (Account_balance) ; when Statement => Order_statement (Account_number) ; when Check_book => Order_checkbook (Account_number) ; end case ; Eject_card ; Print (?Please take your card or press CONTINUE?) ; exit when Card_removed ; end loop ; Update_account_information (Account_number, Amount_dispensed) ; else Retain_card ; end if ; end loop ;

?Ian Sommerville 1995 Software Engineering, 5th edition. Chapter 15 Slide 7