Plug and Play

So, what exactly is Plug-and-Play (PnP)? PnP is a combination of the computer system Basic Input Output System (BIOS), hardware devices, operating system (OS), device drivers, and system resources that dynamically detect and install hardware devices that have been added to a computer system. Rather than requiring a user to know and understand the technical details involved in such a task, PnP will automatically assign the system resources that are needed for the new device and will also locate and install the necessary driver software. In a nutshell, when connecting the new device, a user should be able to turn the computer on and use the new hardware device after PnP installs and configures it. This concept is meant to end the days of manual device configuration and driver conflicts, providing nontechnical computer users with the ability to easily upgrade their computer systems. The goal was to make adding components, such as a printer or scanner, no more difficult than adding a DVD to a television; once a user plugs it in, they can use it.

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Microsoft Building

Microsoft and Flickr

In a narrower sense, PnP is setting bus-resources for the hardware devices. PnP matches devices with their device drivers and specifies their communication channels. With the older ISA bus, before PNP, jumpers were formerly set the bus-resources in hardware devices. Software drivers were assigned bus-resources by configuration files (or the like) or by probing for the device at addresses where they were expected to reside. The PCI bus was PnP-like from the beginning. While the PCI bus specifications do not use the term PnP, it supports in hardware what is today called PnP.

The architecture of the PC provides for only a limited number of Interrupt Requests (IRQ), Direct Memory Access (DMA) channels, Input/Output (I/O) addresses, and memory regions. If there were only a...