PLUG AND PLAY

Plug and Play (PnP) was introduced with Windows 95. It was meant to auto-detect devices that were connected to the computer. This worked well if the devices were plug-and-play compliant. Unfortunately, not all devices meet this standard; those that do not must be configured manually. Three requirements must be met in order to meet the industry-standard definition for plug and play: PnP hardware, PnP BIOS, and PnP operating system.

A plug-and-play BIOS can auto-detect devices connected to the computer and automatically assign resources to them. If a new PnP device is added to a system, the BIOS will check an ESCD (Extended System Configuration Data) database (a running list of active system resources assigned) stored on the CMOS chip to see what resources are unavailable and can be assigned to the new device. In modern computers, the plug-and-play settings are configured in the BIOS under the advanced settings option. Legacy or non-PnP devices are normally configured first; plug-and-play devices are configured next. The following operating systems are considered PnP compliant: Windows 9x, Windows Me, Windows 2000, and Windows XP. For an operating system to use plug-and-play features and recognize new devices, the plug-and-play option in the system BIOS settings must be enabled.