Most network cards use one of four different ways to operate. Polling is one – which involves using the computers microprocessor to examine the system being controlled. Second, a programmed I/O uses the systems address to the bus to create an action. Third, an ‘interrupt driven’ I/O lets the processor known when to send data. Lastly, a DMA allows a component to access the CPM, allowing it to monitor itself. Good thing they’re just plug & play!