I read about how the PC starts up and I am confused.
So at the first level we have the hardware: the PC is made up of multiple sub-systems, each having its own firmware.
So at the second level we have this firmware.
Then at the third level we have BIOS or UEFI.
And then at the fourth level we have the operating system.
Like in this picture:
https://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface
My confusion is with the boot loader, that program that loads the operating system.
From what I read, every operating system has its own boot loader. So I guess that the operating system can be further divided into three levels: boot loader, kernel and shell.
Is this correct?
Sometimes I read that the booting process is the process that starts when you press the button on the PC. And then BIOS is the first program to be executed, and then it loads the boot loader into RAM and then gives control to this boot loader. But hey, I said that the booting process is the process that starts when you press the button on the PC, not the process that starts when BIOS gives control to the boot loader.
So maybe the booting process is the process of loading the operating system, and not the process that starts when you press the button on the PC.
See? So what is the boot software? BIOS + boot loader? Or just the boot? Or what?
So the levels can be: hardware, firmware, bios, os (boot loader, kernel, shell)
or
hardware, firmware, boot (bios, boot loader), os (kernel, shell). But every os has its own boot loader, so this cant be. The first variant must be correct.
But then the booting process is not the process that starts when you press the button on the PC.
So at the first level we have the hardware: the PC is made up of multiple sub-systems, each having its own firmware.
So at the second level we have this firmware.
Then at the third level we have BIOS or UEFI.
And then at the fourth level we have the operating system.
Like in this picture:
https://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface
My confusion is with the boot loader, that program that loads the operating system.
From what I read, every operating system has its own boot loader. So I guess that the operating system can be further divided into three levels: boot loader, kernel and shell.
Is this correct?
Sometimes I read that the booting process is the process that starts when you press the button on the PC. And then BIOS is the first program to be executed, and then it loads the boot loader into RAM and then gives control to this boot loader. But hey, I said that the booting process is the process that starts when you press the button on the PC, not the process that starts when BIOS gives control to the boot loader.
So maybe the booting process is the process of loading the operating system, and not the process that starts when you press the button on the PC.
See? So what is the boot software? BIOS + boot loader? Or just the boot? Or what?
So the levels can be: hardware, firmware, bios, os (boot loader, kernel, shell)
or
hardware, firmware, boot (bios, boot loader), os (kernel, shell). But every os has its own boot loader, so this cant be. The first variant must be correct.
But then the booting process is not the process that starts when you press the button on the PC.