Next to the CPU, the BIOS is the most important chip found on the motherboard. A firmware device, the BIOS provides vital services at bootup, hardware standards for your system and, through its configuration utility, many ways to customize your system. To understand the differences between hardware, software, and firmware, see "The Essential Parts of Any Computer," page 6.
The BIOS (Basic Input Output System) chip performs a variety of important tasks during system operation. On systems that use 32-bit versions of Microsoft Windows (Windows 95 or newer), the BIOS has relatively little to do with system operation after the boot process has been completed. However, during the boot process, the BIOS is an extremely critical component. Tasks that the BIOS chip performs include
Configuration and control of standard devices
The power-on self test (POST)
The location of an operating system, to which it turns over control of the system by using the Bootstrap loader
The CMOS (Complementary Metal-Oxide Semiconductor) chip stores the settings that you make with the BIOS configuration program. The BIOS offers you many different options for most system components controlled by the BIOS, but until the settings are stored in the CMOS, the system is unable to run.