BIOS
{Basic
input/output system}
The classic definition of the
Computer BIOS is, the firmware that gives the Computer its personality. This
definition refers only to functional module of the computer-the one that's
invariably replaced by the
Operating System Code. The nebulous term personality described
how the computer performs its basic functions, those necessary to make it a
real computer.
Programs and the operating systems send commands to the BIOS, and the BIOS sends out the instructions to the hardware using the proper resource values. It lies waiting in your Computer, ready to use.
The Original Goals of the BIOS was
to make computer software "platform independent," meaning that
program don't care what kind of computer they are running on.
The BIOS, like today's driver
software, was meant to wallpaper over the difference in hardware.
The idea although a good one, but
didn't work. Programmers avoided the BIOS in the older computers because it
added an extra software layer that slowed things down. The old hardware-based
BIOS couldn't keep up with changes in the technology. Moreover,
using software drivers allowed hardware engineers to use more memory for the
needed computer code.
The BIOS persist in modern computers
as a common means of accessing hardware before the operating system loads. The
BIOS code of every computer today still includes the equivalent of driver
software to handle accessing floppy disk drives, the keyboard, printers, video
and parallel and serial port operation.
The BIOS of your Computer lingers
around like that unwelcome relative, but it holds the secrets of your computer.
You can lock it up, and even build a wall around it, but it will always be
there. When you switch on your computer, it laughs at you from the monitor
screen. The BIOS of your computer tests your, assures you that everything is
okay when you start your system, helps you set up your computer so that it runs
at its best, and gracefully steps out of the way when you no longer need
it.
ROLES Of The "BIOS"
- The BIOS performs 3 major functions:
- Initializes hardware when the Computer is first turned on.
- Loads the OPerating System
- Provides basic support for the device- keyboard, mouse, and serial ports
- The BIOS resides on a ROM chip
- Non-volatile
- Slower than DRAM
- Loads itself into DRAM
- Uses CMOS
- CMOS is powered by battery, therefore, it is volatile
- Contains BIOS parameter settings for hardware and memory speed.
Functions
The BIOS code of most computers has a number of
separate and distinct functions. The BIOS of typical computers has:
- routines
that test the computers
- block
of data that gives machines its personality
- special
program routines that allows software to take control of computer's
hardware, so that it can more smoothly mesh with the electronics of the
system and even a complete system (in some computers)
- for
determining which expansion boards and peripherals you have installed and
ensuring that they do not conflict in their requests for input/output
ports and memory assignments.
Although all these functions get stored in the
same memory chips, the program code of each function is essentially independent
of the rest. Each function is separate module, and the name BIOS refers to the
entire group of modules.
Power-On Self Test
Every time
your Computer switches on, the BIOS immediately takes command. Its first duty
is to run through a series of diagnostic routines (system checks) called the Power-On Self Test Routine or
POST. This ensures that every part of your computer hardware is functioning
properly before you trust your time and data to it. One by one, the POST
routine checks the circuits of your system board and memory, the keyboard, your
disks and each expansion board. After the BIOS make sure the system is
operating properly, it initializes the electronics so that they are ready for their
first program to load.
Error Codes
The BIOS tests are relatively simple. The BIOS sends data to a port or register and then looks to see the results. If it receives expected results, the BIOS assumes all is well. If it finds a problem, however, it reports the failure as well as it can. If the display system is working, it posts an error-code number on your monitor screen. If your Computer is so ill that the display system is not even work, the BIOS sends a code series of beep through your system's loudspeaker.
Interface Function
Although the primary role for the BIOS today is to get your computer started, it retains the name it earned from its function as the software-to-hardware interface of your machine. It is a control system that operates at the lowest possible level at which the input and output of your computer are designed to link to programs. The BIOS allows your software to press buttons at a distance from the hardware. In operation, the BIOS is a universal remote control.
The original purpose of this one-step-removed BIOS design was to allow computer hardware to be revised and updated without the need to change software correspondingly. The extra BIOS step is needed, because all computers have many hardware elements that are located at specific address.
The BIOS gives the software a link. The software reaches into the BIOS for the hardware it wants. Then the BIOS dips down into the hardware. The new BIOS is an updated roadmap that shows only the detour.
Storage Function
Because the BIOS comes in the physical form of ROM chips, its storage function should not be surprising. The setup memory of your computer is controlled by BIOS functions and is often considered with-and even as a part of the-BIOS. This memory records vital details about your computer hardware so that you don't have to setup each expansion board and disk drive every time you switch on your computer. In addition, the BIOS tell your computer to reserve several small blocks of memory for dynamic data that your computer and its operating system use for tracking several system functions.
Virus
Protection
With all the concern in the industry about computer viruses, some BIOS-makers have added their own form of protection, a warning message that appears when software attempts to write to the boot sector of your hard disk. When the protection is switched on, you're given the option to cancelling the write operation to prevent infection.
The protection afforded by this system is limited in two ways.
- It potentially stops only boot sector virus.
- It does not stop those that afflict the active operating system files.
- It protects, only hard disk controlled through the computer BIOS.
- SCSI (Small Computer System Interface) disks that rely on separate BIOS code in your SCSI host adapter are not protected.
Passwords
Many BIOSs have built-in password protection so that you can limit who uses your computer. The setup program typically gives you the option to enable or disable your password protection. When you enable protection, the system stores your password in its CMOS memory. If the battery that backs up your CMOS gets low, you will lose password protection until you replace the battery.
Other Option
Some BIOSs also offer adjustment for your system's memory cache.
Tuning your system with its BIOS is invitably a trial-and-error experience. You are investing your time to make tests more rigorous than those made by chip manufacturers so that they can run all of your computer's compponents as aclose to the edge as possible.
WRITER: MR. KRISHAN KUMAR SAINI
Today we have learnt about the BIOS {Basic Input and Output Device}. Hope this lesson is helpful for you.
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