BIOS

In IBM PC compatible computers, the Basic Input/Output System, also known as the system BIOS or ROM BIOS, is a de facto standard defining a firmware interface. The name originated from the Basic Input Output System used in the CP/M operating system in 1975. The BIOS software is built into the PC, and is the first software run by a PC when powered on. The fundamental purposes of the BIOS are to initialize and test the system hardware components, and to load an operating system or other programs from a mass memory device. The BIOS provides a consistent way for application programs and operating systems to interact with the keyboard, display, and other input/output devices. Variations in the system hardware are hidden by the BIOS from programs that use BIOS services instead of directly accessing the hardware. The BIOS of the original IBM PC/XT had no interactive user interface. Error messages were displayed on the screen, or coded series of sounds were generated to signal errors. Options on the PC and XT were set by switches and jumpers on the main board and on peripheral cards. Modern Wintel-compatible computers provide a setup routine, accessed at system power-up by a particular key sequence. The user can configure hardware options using the keyboard and video display.

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