The system is composed of till which can access a central resource containing the detailed records of customers’ bank accounts. A till is used by inserting a card and typing in a Personal Identification Number (PIN) which is encoded by the till and compared with a code stored on the card. After successfully identifying themselves to the system, customers may either:

1. make a cash withdrawal or
2. ask for a balance of their account to be printed.

Withdrawals are subject to a user resources, which means the total amount that user has on account. Another restriction is that a withdrawal amount may not be greater than the value of the till local stock.

Tills may keep illegal cards, i.e. after three failed tests for the PIN.

The case has been originally taken from the paper: T. Denvir, J. Oliveira, and N. Plat., The Cash-Point (ATM) ’Problem’, Formal Aspects of Computing, 12(4):211–215, 2000. See also Author's page

Local copy - developers only