Hardware mechanism that enables a device to notify the CPU is called:

Answer: interrupt An interrupt is a hardware signal sent by a device to notify the CPU that it requires attention. The device asserts an interrupt request line or signals through an interrupt controller; the CPU then responds at defined points by running an interrupt handler to service the device. busy-waiting: The CPU repeatedly checks a device’s status in a loop (software-driven), which wastes CPU cycles and is not a hardware notification mechanism.