In personal computers with Windows, ESCD (Extended System Configuration Data) is data that provides a computer's BIOS and the operating system with information for communicating with plug and play (PnP) devices. Full PnP capability requires a PnP BIOS. When a computer is started, the BIOS records in the ESCD information about how older devices are configured to the system. A pre-PnP device has an inflexible configuration (for example, a specified interrupt request setting). PnP-attached devices can automatically be configured around the existing older configurations (or, when necessary, configured manually).