What is BIOS?

BIOS stands for Basic Input Output System. It is a volatile memory (loses all its stored information once the machine is shut down) and so needs CMOS with it, to work properly. If your BIOS is corrupt, your system will never boot.

Bios screen

What does BIOS do?

• The first thing BIOS does is POST (Power On Self Test).
  In POST, BIOS checks if all hard drives, optical drives, floppy disc, ports and other chips on the motherboard are connected, and CPU are working or not and if they meet the requirements to do a successful boot.
• Then BIOS goes to the CMOS to take the configured start-up settings.
  CMOS saves all the settings, and as CMOS is Non-Volatile memory, BIOS checks CMOS to get the configuration, and boot according to the specified settings only.
• Bootstrap Loader
  The job of the microprocessor is to execute programs. But when you start your machine there are no programs to execute. Because the Operating system is not in the memory.
  So the microprocessor goes to the BIOS, the bios takes the start-up settings from CMOS and loads the operating system in memory, and the microprocessor then takes charge of everything.
• Load all the BIOS drivers that give computer control of the I/O devices.

What can you do in bios settings?

You can do a lot of things in BIOS. You can change many things but remember ‘EACH AND EVERY CHANGE CAN AND WILL AFFECT YOUR MACHINE AND BOOT PROCESS.’ Some of the few things you can change in BIOS are:

• Change boot order.
• Set bios password.
• Remove bios password.
• Change all input-output device settings.
• Change memory settings.
• Change CPU settings.
• Change power on settings
• Enable or disable computer logo.
• Change and View fan speed.
• Change default system voltages.
• Change System temperatures.

Working of BIOS in real-time!

1. Performs POST.
2. Checks video-card.
3. Checks CMOS.
4. Checks boot order, and boots accordingly.
5.  If no bootable media is present, boot from hard-disk. Default Operating System is loaded.