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Thank you all very much for your prompt replies. I honestly am sorry for asking amiss, and apologise. I have it down solidly now, and anything else I need to know can be easily subsidized with good old research.

The biggets problem was that I assumed (based on a textbook I have from Uni...I should have known not to trust those thngs) that the Boot order is BIOS -> DOS -> Bootloader.

Where BIOS->DOS is not DOS being loaded, but copied into memory. That was what the textbook stated. It said that Bootup is split into three distinct phases: I'm now typing for the textbook directly:

1. POST
2. Initialization
3. Boot.

Where POST is, a series of self tests performed by the BIOS, Initialization is the phase after POST successful checkup, where DOS and various other components are loaded into memory, and then control is passed to the Bootloader, which is a program stored in the Volume Boot Sector of a bootable device attached to the system.

I assumed that DOS remains in memory, and is able to be interacted with even after the main OS takes over. It also means that i've got a huge misconception about DOS interrupts, which means I need to go and read over a lot of stuff with a new outlook.

And...

I assumed that DOS remains in memory

It is never in memory to begin with.

And what textbook is this?

What? are you serious?

The BIOS is akin to the firmware on other architectures.. it stands for Basic Input/Output System.

Many different implementations exist, but they all are the result of the original IBM PC BIOS being reverse engineered.

Today, the BIOS is primarily used for chipset/device initialization and OS bootstrapping.. but it also offers several legacy Real Mode services, as software interrupts.

Both the BIOS and DOS offered services via interrupts that programmers could use without directly interfacing with the hardware manually.

DOS is just an operating system, a 16-bit Real Mode operating system.. an awful one.. but many implementations exist, like Microsoft's MS-DOS for instance.

It is not part of your computer, nor is it located in ROM.. PC vendors once bundled DOS with their systems, but now many of them include Windows instead.

I personally use neither DOS or Windows, as do many here.. this entire forum is dedicated to operating systems.

All of this information is easy to find, so I question your ability to use a search engine.

@JohnnyTheDon: Course Name: International Diploma in Computer Studies; Module: A+; Textbook: Fundamentals of Hardware and Operating Systems - Hardware Service Technician.

@Brynet-Inc: I diduse Google...I always do...I was just assuming that the textbook wouldn't have been that blatantly wrong. I honestly myself am still surprised it's that wrong. So I was reading the articles I found based on what preconceptions I already had from my textbook.

Anyway: bottom line is, thanks to all of you again, and I wish you the best in your own OS projects.