Question: Explain the routines that executes whenever the system boots up like ROM BIOS routines.

Solution: Whenever PC is turned ON, BIOS takes the control, and it performs a lot of operations. It checks the Hardware, Ports etc and finally it loads the MBR program into memory (RAM).
Now, MBR takes control of the booting process. Functions of MBR, when there is only one OS is installed in the system are as given below:-

1. The boot process starts by executing code in the first sector of the disk, MBR.
2. The MBR looks over the partition table to find the Active Partition.
3. Control is passed to that partition's boot record (PBR) to continue booting.
4. The PBR locates the system-specific boot files (such as Win98's io.sys or WinXP’s ntoskrnl).
5. Then these boot files continue the process of loading and initializing the rest of the OS.