Abstract: A system for performing and recording transactions is used in connection with the vending of articles through vending terminals, especially in vending trolleys on board transportation vehicles, such as airplanes, trains, ferries, and buses. The system includes a computer, a visual display mechanism, and input and output mechanisms. At least part of the input mechanism includes a dynamic key displayed in the display mechanism. The computer includes a random access memory (RAM), and, in a preferred embodiment, the system includes a mechanism for detecting and correcting errors in the RAM that may be introduced by external radiation.