BIOS (Basic Input/Output System) is the firmware that controls and configures the basic hardware settings of a computer, such as the time, date, and boot order. It is typically stored in a non-volatile memory chip on the motherboard and is responsible for:
- Initializing hardware components
- Configuring boot settings
- Providing low-level input/output operations
- Offering a setup interface for users to configure settings.
The BIOS or UEFI is burned into flash memory on the motherboard. At startup it will look for a bootable drive and load an operating system bootloader from the drive.
At that point it turns control over to the operating system’s bootloader which takes care of loading your operating system. Once the operating system is up and running, you can just point and click to load and run any program you want.
- The BIOS performs a power-on self-test (POST) to check if all the hardware components are working properly.
- The BIOS loads the Interrupt handlers and device drivers, It provides a set of Low-level Routine that the operating system uses to interface with different hardware devices, such as the keyboard, screen, and serial and parallel ports.
- The BIOS displays the system settings and determines which devices are bootable.
- The BIOS loads the bootloader from the bootable device, which is typically the hard disk or a USB drive. The bootloader is a small program that resides in the Master Boot Record (MBR) of the bootable device. It is responsible for loading the kernel of the operating system into memory and transferring control to it. The bootloader also provides a menu of boot options if multiple operating systems are installed on the same device
- The bootloader loads the kernel of the operating system into memory.
- The kernel initializes the system processes and device drivers.
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