... In order to achieve this, PnP allocates the following "bus-resources" to both drivers and hardware: I/O addresses, memory regions, IRQs, DMA channels (ISA bus only). ... This is done by allocating bus-resources (I/O, Memory, IRQ's, DMA's) to both the physical device and the device driver software. ... If there were only several devices and they all had standardized bus-resource data (such as unique I/O addresses and IRQ numbers) there would be no problem of attaching device drivers to devices. ...