What Does BIOS Mean?


Every computer, no matter its operating system or specifications, includes a Basic Input/Output System chip on the motherboard. The BIOS regulates the flow of data to and from all the components in the machine. The BIOS also controls the boot process and keeps track of basic computer settings. Though different brands and versions of BIOS exist, their function has changed little over the years.

Boot Fuctions

  • The BIOS controls a computer system through its boot process. When a user presses the power button, the BIOS begins a Power On Self Test to quickly verify all hardware works. After the POST, the BIOS directs the system to the location of the operating system. After the OS loads, the BIOS turns over hardware control to the operating system's drivers, but continues to support the input/output data streams from optical and hard drives.


  • A computer's BIOS stores basic settings, such as boot drive order, clock time, fan speeds and RAM timings on a Complementary Metal Oxide Semiconductor. The CMOS chip, installed separately on a motherboard, draws power from a backup battery in order to retain settings when powered off. Users modify these settings through a setup utility accessible only during the boot process, usually by pressing a certain key immediately after the POST.


  • On older motherboards, the BIOS was stored on a read-only memory chip, making it impossible to update without a hardware upgrade. New BIOS chips use either flash memory or Electrically Erasable Programmable Read-Only Memory -- EEPROM -- which users update through a process called "flashing." Though traditionally done with a specialized boot disk, some motherboards support updating within the operating system.


  • The core structure of BIOS has changed very little over the years. BIOS still uses a 32-bit system while most modern operating systems run in 64-bits. This old technology imposes certain limitations on computers, such as the inability use a boot drive over 3 TB. To fix these problems, a group of major manufacturers created a new boot system, Unified Extensible Firmware Interface. UEFI does not replace BIOS in entirety, but works alongside existing protocols to support new technology. Though not in wide use as of 2011, many UEFI-compatible motherboards are already on the market.


  • Photo Credit bios chip image by Nikolay Okhitin from Fotolia.com
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