The Process of Booting

Steps In the Booting Process:

1. Loading of BIOS: The small set of instructions present in the ROM is loaded into the computer memory and the CPU executes those instructions.
   
   
2. Power-On Self Test (POST): In order to check the operability of all the hardware connected to our computer system, BIOS carries out POST which will check the hardware components and if any problem is found user is alerted with POST beeps and POST screen messaged.
3. Loading of Operating System:
• After the successful completion of POST, the bootable sequence present in CMOS (Common Metal Oxide Semiconductor) is read by BIOS.
• Based on the bootable sequence it will search for Master Boot Record (MBR) in bootable devices like floppy disk, CD-ROM, and hard disk.
• If MBR is not found in any of them, the system will halt by displaying “No Boot Device Found”.
• if MBR is found, the BIOS will load the special application program called Boot Loader, which will eventually load the Operating system.
4. System Configuration is Accomplished: After the OS is loaded, device drivers are loaded into the memory so that our devices can function correctly.
5. System Utilities are Loaded: System utilities like antivirus, volume control, etc. are loaded into the memory in this step
6. User Authentication: If any user authentication is being set, the system will ask the user to enter the credentials, and on receiving the correct credentials the computer system will run GUI shell (in most cases) or CLI shell.

As BIOS is lightweight, it will just load the Boot Loader which can load the Complex set of libraries required for loading the Operating System. BIOS can’t directly load the heavily weighted set of instructions responsible for loading the Operating System.