Special software located in the operating-system kernel that manages and processes system interrupts. Also known as an interrupt service routine (ISR).
When an interrupt occurs, the processor suspends and saves its current activity and then branches to the interrupt handler. This routine processes the interrupt, whether it was generated by the system clock, a keystroke, or a mouse click. When the ISR is complete, it returns control to the suspended process.
Each type of interrupt is processed by its own specific interrupt handler. A table, called the interrupt vector table, maintains a list of addresses for these specific interrupt handlers.
See also hooked vector.