I am starting a project that is a very simple DOS OS, this will be used as a bootloader for DexOS, but will also emulate common Dos int 21h functions and load com/exe files.
So as well as being a bootloader, it will run some Dos programs.
This i hope will form a beginners OS tut.
I know we have freedos, but this will be simpler and coded with fasm.
Simple aims:
1. simple comandline.
2. load com/exe
3. load from fdd,hdd,usb pen drive.
4. emulate about 30 common int 21h functions.
5. easiy to add more function, as needed.

If anyone else is interested in this OS project let me know.

NOTE: Latest Ver is here: http://www.dex-os.com/MiniDos/MiniDos.zip

Screenshot:

hi dex4u.
nice idea !!

is that possible a REAL mode DOS with JIT feature to control memory access? so user application would be JIT (like .net / java) and OS cores / services would be written in asm.

with a .DOS framework!

Hi,
It will be any type of dos people want, as i hope people will add to it, as they see fit.
and yes it will written in asm .

I am interested in the simple D O S
If you have finished
send it to sylwek32 at gmx de please
Thx

It's a project thats just started and we will learn as we go on .

This will be cool!
Although, I'm a beginner at OS coding, I can help the project!
I also want to learn more about OS coding!
And a simple DOS would be a great portable OS!
And if we code some programs for it, we could add some kind of boot sector tools to use as recovery system tool for formating HD's, creating partitions, installing OS... some kind of OS Setup Toolkit!

Sure , i will upload the test demo later to day to show the concept works.

This would be a splendid idea to learn DOS OS creation. Pair with something like Links graphical webbrowser, would re-alive some old Intel based x86 CPU and turn it into a DOS-based mobile device or internet pad.

Yes that would be great, Here is a Demo to test some basic dos functions, less than 600bytes and it run this tasm space invader game perfect , also run my old pascal game too.
http://www.dex-os.com/MiniDos/MiniDos.zip
Runs in qemu too, screenshot:


Will post basic fasm code tomorrow.

Dex, could you please tell me some tutorial or teach me the basics about using QEmu?
I'm very interessed in this emulator, so I can start learning OS coding.

Thanks!


EDIT: I could get Qemu working! It's nice! Now I can learn OS coding without rebooting my machine every time!
Dex, do you have so beginner-friendly OS coding tutorials?

Thanks again!

@Ozzy, That's one of the problems, there are no good easy to follow beginner tut.
Heresthe way i learnt.
1. First you need a bootloader, you can make your own but best to start with one already made.
2. Next you need a format for your simple kernel, but start with a com file, to load this i used "bootprog" http://alexfru.chat.ru/epm.html#bootprog
With this you can load a com or mz exe.
3. Then you start writing bootable program, that do not need Dos function, start with simple print, print hex, time, date etc, than move on to user input and start making a simple command line interface, all in realmode.
This can be all be tested in a emulator.
4. Than start adding your own int or emulating int 21h etc.
You should not move onto pmode until, your OS can load and run its own programs.

PS: What os did you run in qemu ?.
I will add the "Dos4u" as a tut as soon as i finished it .
NOTE: The aim's of "Dos4u" is to be a basic dos in less than 1k, to run some dos programs (games) and be a basic realmode OS tut.

Thanks!
I already can do simple Hello world bootsector program using BIOS Video interrupt. I also can get input using BIOS keyboard interrupt.
I want to know how to use FAT file systems.
I think I'll get book on OS development.

I booted succesfully using Qemu these OS: Dex4u, Damn Small Linux, Slax Linux, and my simple hello world boot program.

I think Dos4u released as tutorial will be great help for newbies like me. And when I learn more about OS, I'll be able to help the project to grow by adding features and post in this forum.

Great, Dex4u OS fasm code and bootprog nasm code has fat file sys, examples .

How to load another sector in Qemu?

First note change of name from "Dos4u" to "MiniDOS".

Here: is the full fasm source code for MiniDos, i have added new functions.
Its now does the following:
Command Line Interface.
Dir.
Loads files .
Runs EXE or COM file.
Runs old Dos programs.
Time.
Date.
Reboot.
Help.
It runs programs code with fasm, tasm, turbo pascal, turbo C etc.
Also implements some dos int 21h functions.
But is still less than 2K, so is good for beginner OS devs, as its fully commented source code.

NOTE: If we all just add one int 21h function, it will quickally build into a good free fasm dos.
There is some limits at the moment like only loading file size of 64k or less.
ScreenShot of MiniDOS running a dos game.

Hi Dex !
Can i use this mini D O S for my embedded game console ?
I want to make something like COMMODORE 64..

So i must change your sourcecode..
Is it okay ?

How to create a disk image ?
WinImage crashes if i select boot.bin

You are free to do with the code anything you like .
There is a image in here:
http://www.dex4u.com/MiniDos//MdosQemu.zip
You use bootable.exe to put boot.bin onto a floppy, if this does not answer your ?, just tell me what you want to do and i will advice you.

ps: This is the mannual for Dex4u boot code, but it users the same tools, it may help
http://www.dex4u.com/bootprog.htm

PPS: If you need to change the code you should only need to change minidos, then just replace the minidos.com on the floppy or image.

"just tell me what you want to do and i will advice you. "

I want do make a OS for embedded PC's to make a GameConsole.
I want to include some emulators

Do you know a emulator for NES <64KB ?
You said it runs only files under 64KB right ?
Or how can i execute "larger" exes ?

Some small nes emulators
http://users.aol.com/autismuk/emu.html
http://users.aol.com/autismuk/tnes2047.zip

Yes it only does 64k file but you can mod the code to load more.
Give me a day or two and i will mod the code to load more.