Hardware/Software layer of an android device I need knowing the differences between a PC hardware and a android device (smartphone), because i have some issues understanding somethings about some subjects.

Generally when I have a computer if I have any restriction , like password in bios or special software into EPROM I need to modify it manually for accessing the PC or make it "totally" under my power.

I want to understand how operators blocks the bootloader of a phone, or "lock" it (not other operators SIMCARDS can work into the device), is this in hardware? Or inside EPROM software? Same way with rooting. If I install a Linux OS in any PC I will be root directly, what happens with the hardware inside smartphones?

Can I have a PC with a network card "locked"? The only way of this is having the eprom of the periphery network card specially programmed.

I think that I need a lot of more knowledge about this subject and I am searching for some books or MOOC that can explain me these specs for deeply understanding the hardware/software interface of an android device phone or any phone in general. I think, for perfectly understand the hardware configuration of any phone device (IOS,Android,windows phone or the nokia stone).

Examples of my problem:


I can have a custom rom in a device, but still is locked, sometimes by software we aim to unlock it, maybe it is inside the software of the GPS antenna?
Sony xperia j st26i "bootloader locked", thats mean, I need to manually flash the eprom for installing a bootloader and custom roms?
Android OS Firmware vs Phone firmware?


Thanks for your help.
Normally, A blocked bootloader means that the bootloader will verify the signature of the installed OS / recovery to be booted. And recovery does not allow you to install a unsigned OS. If you unlock the bootloader, you can "flash" any firmware and the bootloader wont verify the signature. Also, you can now flash a custom recovery that will be able to install from unverified/unsigned sources. Your SIM can be locked at the modem level, bootloader level or at the OS level. It is typically done at modem or bootloader level though.

To unlock a bootloader, you either flash a modified bootloader or switch a flag (as done in nexus devices). root on phone is more or less like sudo.

Android OS firmware may refer to the Android OS (i.e. system, bin, etc. partitions) while Phone firmware is the OS + bootloader + modem and other require bits that are not the part of OS. Things like baseband processor OS, radio drivers,etc are also updated but are not part of android OS.