Stack Memory, or Stack, is a data area or buffer used for storing requests that need to be handled. The IBM Dictionary of Computing says that a stack is always a push-down list, meaning that as new requests come in, they push down the old ones. Another way of looking at a push-down list - or stack - is that the program always takes its next item to handle from the top of the stack. (This is unlike other arrangements such as “FIFO” or “first-in first-out.”)