Interrupt

In computing, an interrupt is an asynchronous signal indicating the need for attention or a synchronous event in software indicating the need for a change in execution. A hardware interrupt causes the processor to save its state of execution, and begin execution of an interrupt handler.  A signal sent to the CPU which temporarily halts the running of a program or process and initiates an interrupt service routine. E.g. Pressing a key on the keyboard, moving a mouse, printer out of paper. Software interrupts are usually implemented as instructions in the instruction set, which cause an interrupt handler to be run similar to a hardware interrupt.

Interrupts are a commonly used technique for computer multitasking, especially in real-time computing. Such a system is said to be interrupt-driven.  An act of interrupting is referred to as an interrupt request (IRQ).

Interrupt handlers are small pieces of software that act as translators between the hardware components and the operating system. For example, when you press a key on your keyboard, the signal is sent to the keyboard interrupt handler, which tells the CPU what it is and passes it on to the operating system. The device drivers are other pieces of software that identify the base hardware components such as keyboard, mouse, hard drive and floppy drive. Since the BIOS is constantly intercepting signals to and from the hardware, it is usually copied, or shadowed, into RAM to run faster.