maintainCases for Example ATM Systemcustomerbanksession .,vvextendin valid PIN - - vtransactionwithdrawalin quirydeposittransferSystem Startup Use CaseThe system is started up when the operator turns the operator switch to the on position. The operator will be asked to enter the amount of money currently in the cash dispenser, and a connection to the bank will be established. Then the servicing of customers can begin.Interaction Diagram System Shutdown Use CaseThe system is shut down when the operator makes sure that no customer is using the machine, and then turns the operator switch to the offposition.The connection to the bank will be shut down. Then the operator is free to remove deposited envelopes, replenish cash and paper, etc.Interaction Diagram Session Use CaseA session is started when a customer inserts an ATM card into the card reader slot of the machine. The ATM pulls the card into the machine and reads it. (If the reader cannot read the card due to improper insertion or a damaged stripe, the card is ejected, an error screen is displayed, and the session isaborted.) Thecustomer isasked to enterhis/her PIN, and is then allowed to perform one or more transactions, choosing from a menu of possible types of transaction in each case. After each transaction, the customer is asked whether he/she would like to perform another. When the customer is through performing transactions, the card is ejected from the machine and the session ends. If a transaction is aborted due to too many invalid PIN entries, the session is also aborted, with the card being retained in the machine.The customer may abort the session by pressing the Cancel key when entering a PIN or choosing a transaction type.Interaction Diagram Transaction Use CaseNote: Transaction is an abstract generalization. Each specific concrete type of transactionimplementscertainoperationsin the appropriateway.The flow of events given here describes the behavior common to all types of transaction. The flows of events for the individual types of transaction (withdrawal, deposit, transfer, inquiry) give the features that are specific to that type of transaction.A transaction use case is started within a session when the customer chooses a transaction type from a menu of options. The customer will be asked to furnish appropriate details (e.g. account(s) involved, amount). Thetransactionwillthenbesenttothebank,alongwithinformationfrom the customers card and the PIN the customer entered.If the bank approves the transaction, any steps needed to complete the transaction (e.g. dispensing cash or accepting an envelope) will be performed, and then areceipt will be printed. Then the customer will be asked whether he/she wishes to do another transaction.If the bank reports that the customers PIN is invalid, the Invalid PIN extension will be performedand then an attempt will be made to continue the transaction. If the customers card is retained due to too many invalid PINs, the transaction will be aborted, and the customer will not be offered the option of doing another.If a transaction is cancelled by the customer, or fails for any reason other than repeated entries of an invalid PIN, a screen will be displayed informing the customer of the reason for the failure of the transaction, and then the customer will be offered the opportunity to do another.The customer may cancel a transaction by pressing the Cancel key as described for each individual type of transaction below.All messages to the bank and responses back are recorded in the ATMs log.Interaction Diagram Withdrawal Transaction Use CaseA withdrawal transaction asks the customer to choose a type of account to withdraw from (e.g. checking) from a menu of possible accounts, and to choose a dollar amount from a menu of possible amounts. The system verifies that it hassufficient money on hand to satisfy the request before sending the transaction to the bank. (If not, the customer is informed and asked to enter a different amount.) If the transaction is approved by the bank, the appropriate amount of cash is dispensed by the machine before it issues a receipt. (The dispensing of cash is also recorded in the ATMs log.)A withdrawal transaction can be cancelled by the customer pressing the Cancel key any time prior to choosing the dollar amount.Interaction Diagram Deposit Transaction Use CaseA deposit transaction asks the customer to choose a type of account to deposit to (e.g. checking)from a menu of possible accounts, andto type in a dollar amounton the keyboard. The transaction is initiallysent to the bank to verify that the ATM can accept a deposit from this customer to this account. If the transaction is approved, the machine accepts an envelope from the customer containing cash and/or checks before it issues a receipt. Once theenvelope has been received, a second message is sent to the b