Interrupts are an asynchronous event mechanism.
The processor doesn't ask devices:
"Do you have an event?"
Devices tell you:
"I need attention"
- Keystroke
- Timer Signal
- Device Operation Completion
- Hardware Error
- The processor stops its current operation
- Saves its state
- Transfers control to a handler
- Returns after processing
Without interrupts:
- I/O is impossible
- Task scheduling is impossible
- The system would be "dead"