BIOS

BIOS is an acronym for Basic Input/Output System and is the built-in firmware that determines what a computer can do without accessing programs from a disk. It is pre-installed on a personal computer’s motherboard and is the first software to run when powered on. The BIOS is typically placed in a ROM chip that comes with the computer and includes instructions on how to load basic computer hardware. Functions of the BIOS include:

  • POST: Used to test the computer hardware and ensures no errors exist before loading the operating system (OS).
  • Bootstrap loader: Used to locate the OS. If a capable OS is found, the BIOS will pass control to it.
  • BIOS drivers: These are low-level drivers that give the computer’s basic operational control over your computer’s hardware.
  • BIOS setup: A configuration program that allows the configuration of hardware settings such as computer passwords, time, and date.

BIOS vs. UEFI

Modern computers use Unified Extensible Firmware Interface (UEFI) firmware, which is the successor to the traditional BIOS. UEFI is responsible for initializing the hardware of a computer before passing control of the hardware to the OS. Although UEFI and BIOS are similar, UEFI offers advanced features over BIOS such as secure boot, low-level cryptography, network authentication, and universal graphic drivers.

Most newer computers support both BIOS and UEFI in order to ease the transition to UEFI and accommodate older operating systems that don’t have built-in UEFI support. In most situations, it doesn’t matter which one is used.

To access the BIOS, the PC will need to be restarted and a key will need to be pressed during the boot-up process. This key is often displayed during the boot process with a message “Press F1 to access BIOS,” “press to enter setup,” or something similar. Common keys to be pressed include Delete, F1, F2, and Escape.

UPDATED: This page was updated April 2021 by Kaiti Norton.

Vangie Beal
Vangie Beal
Vangie Beal is a freelance business and technology writer covering Internet technologies and online business since the late '90s.

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