[SoftWare ] Bios and Importance of bios

[Dark-ImmoRtal^]

The BIOS software has a number of different roles, but its most important role is to load the operating system. When you turn on your computer and the microprocessor tries to execute its first instruction, it has to get that instruction from somewhere. It cannot get it from the operating system because the operating system is located on a hard disk, and the microprocessor cannot get to it without some instructions that tell it how. The BIOS provides those instructions. Some of the other common tasks that the BIOS performs include:

A power-on self-test (POST) for all of the different hardware components in the system to make sure everything is working properly
Activating other BIOS chips on different cards installed in the computer - For example, SCSI and graphics cards often have their own BIOS chips.
Providing a set of low-level routines that the operating system uses to interface to different hardware devices - It is these routines that give the BIOS its name. They manage things like the keyboard, the screen, and the serial and parallel ports, especially when the computer is booting.
Managing a collection of settings for the hard disks, clock, etc.
The BIOS is special software that interfaces the major hardware components of your computer with the operating system. It is usually stored on a Flash memory chip on the motherboard, but sometimes the chip is another type of ROM.

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When you turn on your computer, the BIOS does several things. This is its usual sequence:

Check the CMOS Setup for custom settings
Load the interrupt handlers and device drivers
Initialize registers and power management
Perform the power-on self-test (POST)
Display system settings
Determine which devices are bootable
Initiate the bootstrap sequence
The first thing the BIOS does is check the information stored in a tiny (64 bytes) amount of RAM located on a complementary metal oxide semiconductor (CMOS) chip. The CMOS Setup provides detailed information particular to your system and can be altered as your system changes. The BIOS uses this information to modify or supplement its default programming as needed. We will talk more about these settings later.

Interrupt handlers are small pieces of software that act as translators between the hardware components and the operating system. For example, when you press a key on your keyboard, the signal is sent to the keyboard interrupt handler, which tells the CPU what it is and passes it on to the operating system. The device drivers are other pieces of software that identify the base hardware components such as keyboard, mouse, hard drive and floppy drive. Since the BIOS is constantly intercepting signals to and from the hardware, it is usually copied, or shadowed, into RAM to run faster.

Booting Up
Assuming that everything is working correctly on your computer, the next step that the BIOS takes is to load the operating system into memory. It looks at its settings to determine which drive is designated as the "boot" drive and goes to a special section of that drive to find a small piece of code, sometimes called a Master Boot Record, to load into memory. The code tells the computer how to load the operating system; once it's executed from memory, the computer takes over from the BIOS and starts loading the OS and booting up.

Customizing Your Computer
When you buy a computer, the BIOS frequently comes pre-configured to suit your needs. However, you can change the BIOS settings as well. If you wish to squeeze as much performance out of your computer as possible, you can change configuration options like the CPU clock speed and voltage to force it to run faster. In a business setting, you might choose to prevent the computer from booting from anything other than the hard drive, then enter a password to prevent the setting from being changed. This can stop employees or third parties from using an optical disk or USB drive to boot an alternate operating system, bypass your security, and steal data.

 

Gatekeeping
Once the computer loads the operating system, the BIOS doesn't fade into the background. It's still there providing low-level drivers and information to help the computer's various parts work together. When your operating system needs to talk to the hard drive, for instance, it doesn't have to know how or where your hard drive is attached. It just sends the message to the BIOS, which takes care of passing it along to the correct drive on the correct socket.