Hardware connected to the machine are order of magnitude slower than the CPU. So it is impractical for the CPU to make a hardware access request and then wait indefinitely until the request is completed. Therefore, a more asynchronous approach is necessary.

Polling is a failed approach because it adds overhead to the overall working and performance of the system. The other way is to enable hardware devices to notify the CPU that it needs some attention.

Interrupt

An interrupt is physically produced by electronic signals originating from the hardware devices and directed into input pins on an interrupt controller.