The cash dispenser part is probably just a black box with a simple interface that accepts a message to "dispense some amount of cash" and that can respond "request failed" or "request succeeded". It may even have no concept of inventory and just knows that it tried to dispense X bills and it only got X-1 of them.
Yes, it could have a query function added, and yes the GUI could dynamically respond to that, but it's a bit of an edge case since the assumption is that the ATM is well stocked if it's got mixed bills.
Re:Your ATM does not use transactions
by edoloughlin on Thursday January 10, 2013 @03:27PM
(#5039527)
What drives me nuts is that it knows the smallest denomination at the end of the transaction but out doesn't remember this for the next transaction.
My bank's ATMs display messages like "I only have $50 bills available now", so apparently some ATMs are smarter than others.
- On entering my PIN and selecting the option to withdraw cash, I'm presented with a number of choices (e.g., €20, €50, €90, €200 etc.).
- I select €90 and wait the ~10-20 seconds for the ATM do do whatever it needs to do.
- I'm presented with a message telling me that the machine can only dispense multiples of €50, obviously because it's run out of smaller denominations.
- I'm returned to the 'amount-selection' screen and presented with the same set of choices, including the invalid ones.
I've now wasted almost a minute. Why doesn't the ATM just limit the list to what it's capable of dispensing? Is there some weird security consideration I'm missing?