What is mean by interrupt vector table?

Answer 1

the memory address of an interrupt handler or an index into an array is called interrupt vector table. interrupt vector table contain the memory adress of interrupt handler.

Answer 2

Interrupts are essential to the operation of a computer because they allow it to process service requests. Interrupts tell the computer to stop whatever it is doing and start some other task, such as handing the keyboard or mouse movement. When the task is complete, the interrupt finishes and the computer resumes whatever it was doing previously. Interrupt vectors allow for compatibility, since interrupt numbers can be standardized, and different interrupt code installed for similar devices from different vendors.

An interrupt vector table separates a hardware device that has events from the code that will process that event. A device (i.e. network card, keyboard, mouse, etc) generates an event and that event needs to trigger a message into some software application. That message might ultimately be ignored, but the responsibility of the hardware is to get that event into the computer. Hardware devices simply change state when events happen which then causes a memory mapped location for the hardware to change.

This change then triggers the OS to perform a simple look-up in the interrupt vector table and jump at the machine level to the machine code that will handle the interrupt. The machine code to handle the interrupt is known as the device driver or interrupt handler. That code will read any memory mapped locations related to the event and pass that information on to higher level software routines.

The simplicity of the interrupt vector table allows a complete separation between hardware devices and software OS. This is what allows a USB mouse to be used on different OS on a single machine or across different hardware architectures (i.e. Mac, Intel PC, etc).

The necessary evil of this scheme is that you can't use a device with an OS if there is no device driver for that OS. This is particularly frustrating to users who have a device that has a driver with one version of an OS "X", upgrades the OS to the next version "X+1", and finds that the driver philosophy has changed in "X+1" and the device can no longer be used.