The BIOS controls the proper setup and configuration of hard disk drives, floppy drives, memory, and other related devices at the hardware layer. It also has some control over how an operating system interacts during boot up.
If you add a new hard disk drive, it’s the BIOS that will see the drive first. It will then attempt to configure it according to the manufacturer's specifications ( for example, the number of tracks, cylinders, and sector size will all be configured automatically by the BIOS so that the operating system can properly recognize and use the drive).
If you add additional memory to a system, the BIOS handles all updates and counts the quantity of memory installed and return an error code, if a problem exists. The BIOS also sets all configuration items required for the memory to function properly in the system, including speed and voltage requirements. The BIOS is also in total control of the system boot up process. When you first turn on the computer, the BIOS performs what is known as a Power On Self Test (POST) routine which consists of a series of tests tests to ensure devices are working properly. You can think of this test as a sort of computer hardware inventory system each time the computer boots up. make sure all devices in the system are functioning properly and checks to see whether other devices, such as a video graphics adapter has its own BIOS that needs to be run during boot up.
The pages contained within this section are devoted to helping you understand the complexities of a Basic Input / Output System.