Event Driven Devices - Polling
Polling: The status of all devices is periodically checked in a repetitive manner through a polling loop. While an event happens, the loop is exited and the consequent event is handled by executing some special event-handling routine or task. Again the polling carries on. The disadvantage is, the processor has to stay in an idle state till some event happens. Data entered can be missing if an event happens at a time while the major program is not in its polling loop.