2. What is Bios?
TheBIOSis boot firmware, designed to be the
first code run by aPCwhen powered on. The
initial function of the BIOSis to identify, test,
and initialize system devices suchasthe video
display card, hard disk, floppy disk and other
hardware. TheBIOSsets the machine hardware
into aknown state, sothat software stored on
compatible media canbe loaded, executed,
and given control of thePC.
4. The BIOS in a PC comes
from three possible
sources:
• Motherboard ROM
• Adapter card ROM(such asthat found
on avideo card)
• Loaded into RAMfrom disk(device
drivers)
5. Motherboard Bios
All motherboards must have aspecial chip containing software
called the ROMBIOS.ThisROMchip contains the startup
programs and drivers used to get the system running and act as
the interface to the basic hardware in the system. When you
turn on asystem, the power on self test (POST)in the BIOSalso
tests the major components in the system.Additionally, you can
run asetup program to store system configuration data in the
CMOSmemory, which is powered by abattery on the
motherboard. ThisCMOSRAMis often called NVRAM
(nonvolatile RAM) because it runs on about 1 millionth of an amp
of electrical current and can store data for years when powered
by atiny lithium battery.
7. ThePOSTtests your computer's processor,
memory, chipset, video adapter, disk
controllers, disk drives, keyboard, andother
crucial components.
POST (power on self
test).
8. Setup
Thesystem configuration and setup program is usually a
menu-driven program activated by pressing aspecial
key during the POST
,and it enables you to configurethe
motherboard and chipset settings along with the date
and time, passwords,disk drives, and other basicsystem
settings. Youalso can control the power-management
settings and boot-drive sequence from the BIOSSetup,
and on some systems, you can also configure CPU
timing and clock-multiplier settings.
10. Bootstrap loader
Aroutine that reads the first physical sector of
various disk drives looking for avalid master
boot record (MBR). If one meeting certain
minimum criteria (ending in thesignature bytes
55AAh) is found, the code within isexecuted.
TheMBRprogram code then continues the boot
process by reading the first physical sector of
the bootable volume, which is the start of the
volume boot record(VBR).
