System BIOS`

System BIOS

BIOS stands for Basic Input/output System, although the full term is used very infrequently. The system BIOS is the lowest-level software in the computer; it acts as an interface between the hardware (especially the chipset and processor) and the operating system. The BIOS provides access to the system hardware and enables the creation of the higher-level operating systems (DOS, Windows 95, etc.) that you use to run your applications. The BIOS is also responsible for allowing you to control your computer's hardware settings, for booting up the machine when you turn on the power or hit the reset button, and various other system functions.

This section takes a look at the various functions that the BIOS performs, and discusses some of its characteristics. In addition to what is discussed in the sections below, the BIOS's other main responsibilities include and providing the allows you to change BIOS parameters.

System Boot Sequence

The system BIOS is what starts the computer running when you turn it on. The following are the steps that a typical boot sequence involves. Of course this will vary by the manufacturer of your hardware, BIOS, etc., and especially by what peripherals you have in the PC. Here is what generally happens when you turn on your system power:

The BIOS begins the search for a drive to boot from. Most modern Boise's contain a setting that controls if the system should first try to boot from the floppy disk (A :) or first try the hard disk (C :). Some Boise's will even let you boot from your CD-ROM drive or other devices, depending on the 98 this process is called a "cold boot" (since the machine was off, or cold, when it started). A "warm boot" is the same thing except it occurs when the machine is rebooted using {Ctrl} + {Alt} + {Delete} or similar. In this case the POST is skipped and the boot process continues roughly at step 8 above.