What is BIOS ?

Lets start with the basics of computer:

BIOS (Basic Input Output System) BIOS is software stored in a ROM (read only memory) chip located in the motherboard of a PC. It is the first code run when the computer is turned on. When you start your computer, the CPU (Central Processing Unit), sends control of the PC to the BIOS routine. After the CPU gives the BIOS the "go ahead", it begins looking for all the components and peripheral devices attached to your computer. The CMOS memory chip (complementary metal oxide semiconductor) stores the data that is used by the BIOS setup and testing routines.When the computer is turned on(or booted) the BIOS runs a set of routines that tests the hardware, starts the operating system, and supports the transfer of data between hardware devices at startup. In most PCs, the BIOS has 4 main functions.

• POST - Tests computer hardware, ensuring hardware is properly functioning before starting process of loading operating system.  
• Bootstrap Loader - Process of locating the operating system. If capable operating system located, BIOS will pass the control to it.
• BIOS - Software and drivers that interface between the operating system and your hardware. When running DOS or Windows you are using complete BIOS support.
• BIOS / CMOS Setup - Configuration program that allows you to configure hardware settings including system settings such as computer passwords, time, and date.

While running the POST (power on self test) if any fatal errors occur the boot process stops. A sequence of beeps will sound which identifies where the problem is.
Following figure shows BIOS interface:

And following figure shows the BIOS chip: (may change from computer to computer)

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Shantanu

Posted in: Hardware