flat assembler - FDOS - DOS-like os in FASM

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Victor Kindhart

Joined: 02 Feb 2015
Posts: 7

Victor Kindhart 17 Jun 2015, 17:48

My first 16-bit OS here - FDOS (aka FASM DOS). I am trying to create a Real Mode OS which will resemble MS-DOS tho it won't be compatible with it. GitHub repo is here: https://github.com/Vik2015/fdos

My question is, does anybody know how would I add a FAT12/16 support to my OS so I could load programs?[/url]

Last edited by Victor Kindhart on 17 Jun 2015, 21:46; edited 1 time in total

17 Jun 2015, 17:48

Mike Gonta

Joined: 26 Dec 2010
Posts: 243

Mike Gonta 17 Jun 2015, 20:53

Victor Kindhart wrote:

My first 16-bit OS here - FDOS (aka FASM DOS). I am trying to create a Real Mode OS which will resemble
MS-DOS tho it won't be compatible with it. GitHub repo is here: https://github.com/Vik2015/fdos

Oops, you've got the period in the url.

Victor Kindhart wrote:

My question is, does anybody know how would I add a FAT12/16 handler to my OS so I could load programs?

Have you seen this.

A more livelier discussion of when DOS is not DOS is here.

PS. Have you seen MikeOS32

_________________
Mike Gonta
look and see - many look but few see

https://mikegonta.com

17 Jun 2015, 20:53

Victor Kindhart

Joined: 02 Feb 2015
Posts: 7

Victor Kindhart 17 Jun 2015, 21:58

Mike Gonta wrote:

Victor Kindhart wrote:
My first 16-bit OS here - FDOS (aka FASM DOS). I am trying to create a Real Mode OS which will resemble
MS-DOS tho it won't be compatible with it. GitHub repo is here: https://github.com/Vik2015/fdos
Oops, you've got the period in the url.
Victor Kindhart wrote:
My question is, does anybody know how would I add a FAT12/16 handler to my OS so I could load programs?
Have you seen this.

A more livelier discussion of when DOS is not DOS is here.

PS. Have you seen MikeOS32

Dot removed Smile

And I know what MikeOS is - it was the first tutorial on OS deving I found. Gonna read that other page now.

Btw, do you know how can I make a bootable floppy? AFAIK a typical floppy disk has at least one sector in the start of floppy, which contains a jump, label, etc. And it also contains a small amount of code only to display "This is not a bootable floppy...". I've tried to find some software which can help me create a bootable floppy - I could have a bootloader there with FAT 12/16 support which would find my kernel on the floppy and load it into memory (gonna change that to loading to high memory) and running it, but failed - the only thing I managed to find was A LOT of tutorials on how to create a repair/reserve floppy disk on linux :/. Actually I COULD write my own program tho I'd like to use a real soft, not some dirty hack Smile

17 Jun 2015, 21:58

Mike Gonta

Joined: 26 Dec 2010
Posts: 243

Mike Gonta 17 Jun 2015, 22:19

Victor Kindhart wrote:

Mike Gonta wrote:
Have you seen MikeOS32
And I know what MikeOS is - it was the first tutorial on OS deving I found.

Then take a look at MikeOS32 and say goodbye to real mode code.

Victor Kindhart wrote:

Btw, do you know how can I make a bootable floppy?

Say goodbye to that too and make a bootable USB flash drive.

_________________
Mike Gonta
look and see - many look but few see

https://mikegonta.com

17 Jun 2015, 22:19

Victor Kindhart

Joined: 02 Feb 2015
Posts: 7

Victor Kindhart 17 Jun 2015, 22:52

Mike Gonta wrote:

Victor Kindhart wrote:

Mike Gonta wrote:
Have you seen MikeOS32
And I know what MikeOS is - it was the first tutorial on OS deving I found.
Then take a look at MikeOS32 and say goodbye to real mode code.
Victor Kindhart wrote:
Btw, do you know how can I make a bootable floppy?
Say goodbye to that too and make a bootable USB flash drive.

That is the point. I am trying to write it using 16-bit code Smile

And I suppose I can install FAT system in USB drive? It seems like the easiest one to handle.

17 Jun 2015, 22:52

cod3b453

Joined: 25 Aug 2004
Posts: 618

cod3b453 10 Jul 2015, 20:47

You can create a bootable image in FASM; the only real requirement is that the signature be present at the end of the sector for the BIOS to start executing it. The jump is optional but a good way of forcing cs:ip to be expected values.

Code:

        format binary as 'img'

SECTOR_SIZE equ 512

org $7C00

start_of_sector:

        jmp 0:start

    start:

        ; code here

        times (SECTOR_SIZE - (end_of_sector - signature) - ($ - start_of_sector)) db 0

        signature dw 0xAA55

end_of_sector:

This can be extended to include FAT tables and file system images, including the second stage bootloader/kernel etc. [You can also use the code for hard disk, usb and CD-with-floppy-emulation images.]

10 Jul 2015, 20:47

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