Automated Teller Machines (ATMs), in more than fifty years of existence, have undergone numerous changes, which have helped in enriching the relationship between the banks and their customers. The ATMs which started out as cash dispensing machines have come a long way in disrupting the way customers interact with banks. Throughout the evolution of the ATM, one element which has undergone minimal change, is the operating system (OS). Since the demise of OS2, ATMs across the world have without exception run the MS Windows OS.