The BIOS of your computer is the Basic Input Output System.
It's the firmware or the software
that's used to get your computer running.
Sometimes you'll hear this referred to as the system
BIOS or the ROM BIOS.
The term ROM BIOS refers back to the days when this software was
stored on Read Only Memory chips that were on the motherboard.
Our modern computers store this BIOS software in flash memory,
so we're able to upgrade the BIOS by using an application
rather than removing chips and replacing chips
on the motherboard.
When you first turn your computer on,
the BIOS initializes the memory and performs
a check of your system.
This check is called a Power On Self-test or a POST.
The POST process will look for a CPU, for memory,
will check to see that you have a display connected
and a keyboard.
And if all of the hardware passes these diagnostics,
it then begins to look for a boot loader on a storage device
to load the operating system.
If you look closely at your motherboard,
you'll probably be able to find the flash memory that
holds that BIOS software.
In this particular motherboard, there is a main BIOS
and then there's a backup BIOS.
This allows you to easily perform upgrades to the BIOS
and then be able to switch back and forth
between different BIOS versions.
There are two different types of BIOS that you
might find on a computer.
The first is what we call a legacy BIOS.
This is the BIOS that's been around for well over 25 years.
Older operating systems would communicate through this BIOS
to gain access to the hardware of the computer.
This legacy BIOS was designed for an older type of hardware.
So access to USB interfaces, network interfaces,
or some of our modern storage devices
wasn't possible through a legacy BIOS.
A much more common BIOS these days is the UEFI BIOS.
This stands for Unified Extensible Firmware Interface,
and it's based on a BIOS type that Intel
created called the EFI BIOS.
This standard was created so that all
of the motherboard manufacturers could
use a standard type of BIOS across
every single manufacturer.
These UEFI BIOS is designed to completely replace the legacy
BIOS and it provides support for all of our modern hardware.
You might also find a more graphical front
end, which makes it a little bit easier to use.
But there are options to also use a text-based front
end as well.
The UEFI BIOS brings with it a number of advantages.
One is that it's able to boot from very large drives that
are over 2.2 terabytes in size that have been formatted
with the GUID partition table.
That's the globally unique identifier.
You may sometimes see this referred to as GPT disks.
UEFI BIOS can also boot from File Allocation Table or FAT
formatted drives, and it does support removable media
as well so you can boot from a USB flash drive.
From a troubleshooting perspective,
one of the advantages of UEFI BIOS
is that we have a pre-boot environment.
You can think of this as a mini operating system that has
its own drivers, its own shell.
We can run applications.
This allows us to browse the internet, backup drives that
are on the system, be able to access the network all
without booting a full-blown operating system.
We can do this all from the UEFI BIOS.
When you make changes to the BIOS configuration,
you need somewhere on your system to store those changes.
Those changes are stored in non-volatile BIOS memory.
This memory is usually flash memory
that's on the motherboard that stores all of our BIOS
configuration settings.
Before we had flash memory to store these BIOS configuration
settings, we stored everything on Complementary Metal Oxide
Semiconductors or CMOS.
The CMOS allowed us to write and then change the information
on the CMOS, and then there was a battery
on the motherboard that made sure that that information was
constantly refreshed so we didn't lose our configurations.
These days, of course, we have flash
memory and our BIOS configurations
are stored on flash, which means we don't have to have a battery
or constantly provide power to maintain those configurations.
Even though we're using this flash memory these days
instead of CMOS, you'll still hear
people refer to that configuration setting area
as the CMOS or the CMOS settings.
When we refer to the CMOS today, we're
really referring to the data that we're
storing into flash memory that contains the BIOS configuration
settings.
If you look closely at the motherboard of your computer,
you'll probably see there is a battery on the motherboard.
On this particular motherboard, it's right next to the CPU.
Since we're not using CMOS to store a BIOS configuration
settings, this battery is most commonly
used to maintain the data and the time on this computer.
These batteries can last for years.
But if the battery does lose its charge,
you'll find that your computer is not
able to maintain the date and time if you happen to remove
the power from your computer.
Since the battery on our older CMOS systems
was designed to maintain the BIOS configurations if you
simply remove the battery, then you're
also clearing out all of the BIOS configurations
including any passwords that might have been
used for supervisor access.
On these newer motherboards, there's
usually a jumper that you'll connect, power on the system,
and that jumper would tell the flash memory to clear out all
of your BIOS configurations.