Let us consider the behaviour specification of a simple state-chart for an Automated Transfer Machine (ATM) for banking transactions. It has a slot to hold the bank card for reading and writing and a slot for withdrawing money. Also, it has an interface with a screen to display messages (e.g., options, validation), ten buttons representing the digits for keying the Personal Identification Number (PIN), and three more buttons for clear, cancel, and enter. For simplicity, we shall consider only the validation of the traditional service of an ATM, namely inserting card, PIN, and their validation. A partial state-chart for specifying the IDLE and a composite validation state is shown below. Continue this state-chart by specifying a transaction of money withdraw for the case when Validating card & PIN is valid.

Validatian igit tting PDS EtaE aturn card) -Inat vali4] Validating Eject card