It will not be an exaggeration to say that PC is the most widely used electronics gadget in the world today. Like any other machine PC could be malfunctioning sometimes. To restore the PC into its normal health, PC support is must. For repairing the PC, knowledge of PC components is essential. The firmware interface is one of the most indispensable PC components. Basic Input and Output System (BIOS in short form) is the de facto standard of firmware interface. Awareness of BIOS is prerequisite for repairing PC hardware.

BIOS features

BIOS is nothing but a software embedded in a non volatile ROM chip on the motherboard. BIOS is also known as Basic Integrating Operating System.

Purpose of using the BIOS

The main purpose of BIOS is to load and start the operating system. Before doing that it checks the presence of different hardware components including display,keyboard,Memory,hard drive,floppy drive, optical drive etc . It runs some diagnostic routines on those devices and control them. If all the hardware components are found to be in proper working condition, it performs the configuration of all components. Else it reports the fault report to the user.

User Interface of the BIOS

The interface menu system could be accessed by hitting a certain key during the PC booting up period. The following operations could be performed by using the BIOS interface:

1. Hardware configurations

2. Activating and deactivating system components

3. Password prompt setting

4. System clock setting

5. Selecting a booting device

6. Modifying memory settings

7. Changing power on settings

8. Changing fan speed settings

BIOS library

The BIOS features a library of input and output functions. These functions could be called to control the operations of peripherals, such as keyboard,display,etc. External software could invoke these functions too. In certain PCs few peripherals come with their own bios that features more functionality.

Evolution of BIOS

BIOS has been evolving over times. Though BIOS is still widely used, but it is gradually being replaced by Extensible Firmware Interface (EFI in short form). However right now EFI is being used by Windows OS supporting GPT and Linux Kernel 2.6.1.

Hardware Architecture

Generally BIOS is designed for 16 bit and 32 bit architecture. EFI is written for 64 bit architecture. In the 16 bit architecture BIOS routines used to be invoked by operating systems to access hardware. In the 32 bit architecture the operating systems directly access the hardware by invoking their own device drivers.

Programming the BIOS

In the earlier version of PCs, BIOS used to be programmed into non volatile ROM. In the modern versions of PCs, BIOS is stored into rewritable memory. Thus the BIOS content could be rewritten. The rewriting of BIOS is also known as flashing. Flashing is performed by a special program. The flashing program is generally provided by the systems manufacturer. The flashing is generally done to upgrade the BIOS to a new version to fix bugs or to improve performance or to support new PC hardware.

BIOS Over-locking

In the BIOS over-locking process the speed of the CPU could be increased from the factory preset value. Over-locking makes the PC faster. But over-locking reduces the life span of the CPU.

Virus Attack On BIOS

The number of viruses that attack BIOS is very less, just 3. Two of those viruses were created for demonstration purpose. Those two viruses are "CIH" and "Black Hat 2006". The third virus is called "Persistent BIOS infection". To ensure that BIOS is virus free, virus removal program should be run periodically.