BIOS abbreviation Basic Input Output System, is a non-volatile firmware used to perform hardware initialization during the booting process of a computer. It provide runtime services for operating systems and programs. It also manages data flow between the computer's operating system and attached devices such as the hard disk, video adapter, keyboard, mouse and printer.

The BIOS includes instructions on how to load basic computer hardware and includes a test referred to as a POST (Power On Self Test) that helps verify the computer meets requirements to boot up properly. If the computer does not pass the POST, you will receive a combination of beeps indicating what is malfunctioning within the computer.

The BIOS firmware comes pre-installed on a personal computer's system board. BIOS is a program that is made accessible to the microprocessor on an erasable programmable read-only memory chip. When you turn on your computer, the microprocessor passes controlto the BIOS program, which is always located at the same place onEPROM.

When BIOS boots up your computer, it first determines whether all of the attachments are in place and operational and then it loads the operating system into your computer's random access memory from your hard disk or diskette drive.

BIOS boots by reading the first sector on a hard disk and executing it,this boot sector in turn locates and runs additional code. The BIOS system is very limiting because of space constraints and because BIOS runs 16-bit code, whereas modern computers use 32-bit or 64-bit CPUs.




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