Question: what are the four main parts of the boot process?
Answer: The POST Process. Once your PC has been powered on, the BIOS begins its work as part of the POST (Power-On Self Test) process. ... 
BIOS Boot Handoff. ... 
The Partition Table. ... 
Bootstrap Code. ... 
Boot Signature. ... 
The second-stage bootloader. ... 
Boot Configuration Files. ... 
Popular Bootloaders.