THE BIOS(Basic Input Output System) provides the microprocessor with all the information required to boot the system. It is an electronic set of instruction used by the computer to start operating.
The main function of BIOS is to give instruction to the POST(Power On Self Test). In this test, all the components and their functionality is checked. If there is a problem it generates a beep from the computer´s built in speaker. Different beep is generated for different situations. For example, if the CMOS battery is not working properly, it will generate two beeps. The BIOS also interacts with the drives setting and components, such as load the operating system from the HDD to the ROM chip.
When we start our computer there is an operation performed automatically. System will check all the software and hardware which are installed or attached to the system.