The devices in your PC, keyboard, mouse, CD-ROM, sound card, scanner, printer, modem, monitor, disk drives, etc. In some older PCs, these resources are very limited. This can lead to resource conflicts which is one of the most common problems encountered when configuring new PCs and adding devices in already-configured PCs. It is also one of the most difficult to diagnose and correct. A hardware interrupt occurs when a device needs the attention of the CPU or wants to make the CPU aware of a change of its status.
Interrupt signals can come from a variety of sources.
A keystroke, for example, generates an interrupt signal. Since the introduction of the 286 PC, however, there are now 16 IRQ lines. IRQs 0 to 7 are mapped to Interrupt 8 to15. IRQ 9 is remapped to IRQ 2. If you install hardware that uses IRQ signals, hopefully you will be able to choose an IRQ line.