An IRQ is an interrupt request from a device.Currently they can come in over a pin, or over a packet.Several devices may be connected to the same pin thussharing an IRQ.An IRQ number is a kernel identifier used to talk about a hardwareinterrupt source. Typically this is an index into the global irq_descarray, but except for what linux/interrupt.h implements the detailsare architecture specific.An IRQ number is an enumeration of the possible interrupt sources on amachine. Typically what is enumerated is the number of input pins onall of the interrupt controller in the system. In the case of ISAwhat is enumerated are the 16 input pins on the two i8259 interruptcontrollers.Architectures can assign additional meaning to the IRQ numbers, andare encouraged to in the case where there is any manual configurationof the hardware involved. The ISA IRQs are a classic example ofassigning this kind of additional meaning.