Polling
Repeatedly checking whether a component needs attention, rather than waiting to be told.
Glossary
Interrupt
A signal from hardware that asks the system to turn its attention to something now.
In one line
A signal from hardware that asks the system to turn its attention to something now.
Also calledhardware signal
An interrupt is a gentle tap on the shoulder. Rather than making the system constantly check whether a component needs anything, the component raises an interrupt to say, in effect, I have something for you now. The system can then attend to it promptly and return to what it was doing.
A driver responds to these signals, handling each one quickly so the system can return to whatever it was doing. It is a far more efficient arrangement than constant checking, because the system spends its effort on real work rather than on asking the same empty question again and again.
Interrupts must be handled with speed and care. While one is being dealt with, other work waits, so the response is kept short and focused, doing just enough to acknowledge the event and noting any larger task to finish later. This keeps the whole system feeling responsive.
When many interrupts arrive at once, the system uses priorities to decide what to address first. Something urgent is attended to ahead of something that can wait, which is part of how a busy machine stays calm under pressure instead of falling behind.
In practice
In practice, an interrupt is like a doorbell. You do not stand by the door all day checking whether someone has arrived; you get on with your work and answer when it rings. Hardware uses the same idea, ringing for attention only when it actually has something for the system to handle.
