In the IO hardware lesson, we learned that interrupts are hardware mechanisms that send signals when an IO device needs the computer’s attention.
Interrupt handlers refer to the software components that manage the pool of interrupts that are sent to the CPU. Interrupt handlers receive and acknowledge that a signal has been received, place it in a queue, and execute the interrupts by priority. When an interrupt is received the interrupt handler notifies the CPU. The CPU will then halt its current processes, and wait for the execution of the interrupt before continuing.
Consider pressing a keyboard button and trying to turn up the volume on a computer at the same time. Although it may seem to be simultaneous, the computer will place both in a queue based on when the signal is received by the interrupt handler. Once the interrupt by the first is completed (e.g. the keyboard button is displayed on a word processing document), the second one will begin execution (the volume is adjusted).
Take a look at the animation to the right. This animation shows how multiple IO requests that are made almost simultaneously are processed by interrupt handlers through execution.