Editing BIOS (section)

== {{Anchor|BCU}}User interface ==
The BIOS of the original [[IBM Personal Computer|IBM PC]] and [[IBM Personal Computer XT|XT]] had no interactive user interface. Error codes or messages were displayed on the screen, or coded series of sounds were generated to signal errors when the [[power-on self-test]] (POST) had not proceeded to the point of successfully initializing a video display adapter. Options on the IBM PC and XT were set by switches and jumpers on the main board and on [[expansion card]]s. Starting around the mid-1990s, it became typical for the BIOS ROM to include a ''"BIOS configuration utility"'' (BCU<ref>{{cite web
 |url         = http://ftp.hp.com/pub/caps-softpaq/cmit/HP_BCU.html
 |title       = HP BIOS Configuration Utility
 |year        = 2013
 |access-date = 2015-01-12
 |publisher   = [[Hewlett-Packard]]
 |url-status  = live
 |archive-url = https://web.archive.org/web/20150112201124/http://ftp.hp.com/pub/caps-softpaq/cmit/HP_BCU.html
 |archive-date= 2015-01-12
 }}</ref>) or "BIOS setup utility", accessed at system power-up by a particular key sequence. This program allowed the user to set system configuration options, of the type formerly set using [[DIP switch]]es, through an interactive menu system controlled through the keyboard. In the interim period, IBM-compatible PCs{{mdashb}}including the [[IBM Personal Computer/AT|IBM AT]]{{mdashb}}held configuration settings in battery-backed RAM and used a bootable configuration program on floppy disk, not in the ROM, to set the configuration options contained in this memory. The floppy disk was supplied with the computer, and if it was lost the system settings could not be changed. The same applied in general to computers with an [[Extended Industry Standard Architecture|EISA]] bus, for which the configuration program was called an EISA Configuration Utility (ECU).

A modern [[Wintel]]-compatible computer provides a setup routine essentially unchanged in nature from the ROM-resident BIOS setup utilities of the late 1990s; the user can configure hardware options using the keyboard and video display. The modern Wintel machine may store the BIOS configuration settings in flash ROM, perhaps the same flash ROM that holds the BIOS itself.