LINUX

ZERO TO GUI

power on >> BIOS >> MBR(first sector pf hard disk) >>boot loader >> kernal(linux os)u

kernal >> intial RAM disk (initramfs image) >> /sbin/init(parent proccess)>> cmd shell>>GUI

BIOS 

after power on bios installise hardware monitor, keyboard, mouse, hardisk etc.

bios software is stored in the rom chip on the motherboard

after choosing bootdevice and os ,bios job is done

MBR(master boot record &boot loader)

boot loader is stored in EFI partition 

there after information on date and time and the most impotant are loaded from CMOS values 

types of bootloader exist : GRUB, ISOLINUX , DAS U-Boot 

bootable partiton  search for ISOLINUX and loads it into ram