Protected Mode, OS Development, Docs and Tutorials


Tiny OS Kernel

I didn't have to do anything sometime ago and I started then programming an OS. It seems that I still don't quit starting serious, global and complex projects. ;))

I program the OS with my friend - Gennady Proschaev (we discuss details, find and fix bugs together). His coordinates go here:

Homepage =
E-mail =

I would like you to memorize that:


This program shows the basics of system programming for protected mode.


- 32-bit Protected Mode Programming with 386+
- Exceptions Handling
- Timer & Keyboard Hardware Interrupts Handling
- Task Switching (Ring 0 and Ring 3 Tasks)

System Requirements

- 386 or better computer
- EGA/VGA or better color video system
- DOS 5.0 or better (without any  memory  managers  such  as  HIMEM.SYS  and EMM386.EXE) or Windows 9x loaded in the Command Prompt Only mode

Known Bugs and Problems

- Those ones I've found myself are now fixed! ;) - 20KB (TAsm 3.2+/MASM 6.11) 30th of May 2000

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Page Translation Tutorial

Two versions of the program (PAGING and NOPAGING) differ only in one  thing. The first one sets the PG bit of the CR0 register to "1", but the second  one doesn't do that. The result is also different. Programs draw colored bars on the screen in a different order.  That's because  Page Table  setup so that a linear address doesn't equal to a physical address everywhere. Detailed, order of pages that correspond to the VGA graphics buffer is opposite to the normal order. - 28KB (TAsm 3.2+/MASM 6.11) 30th of May 2000

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V86 Mode Monitor Tutorial

This program is intended to show how a V86 monitor should work. It sets up a V86 mode and launches a command interpreter (COMMAND.COM).


Tested on a Wolfenstein 3d and worked fine ;-) - 28KB (TAsm 3.2+/MASM 6.11) 30th of May 2000

Unfortunately, I discovered that this program sometimes doesn't work. There must be a bug which I'm not gonna fix because the source code is huge and old. Better visit the following site because v86 stuff presented there is much simpler and really works: - PMode Tutorials in C and Asm

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Here goes a set of utils that allow you to make 32-bit programs for Protected Mode (not for DPMI!!!) very easily with DJGPP C compiler and/or NASM assembler. These utils simply make ready-relocated flat executable programs out of COFF ".o" object files. Such executable programs are really easy to load and run, since there is not needed relocation process any more. I've written all these utils because programming entire programs for PMode in pure x86 assembly language is too boring for me. I've been interested in how to use a C or Pascal compiler for that. So here they are...

Short description

Assembly example program simply prints a standard "hello world!" message to the screen and quits.

C example program is more advanced:

Well, don't waste time anymore and download the utils. Have fun! Feedback is welcome! - approx. 180KB - approx. 5KB - approx. 40KB

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Boot sector that loads and runs COM/EXE programs

When people develop bootable projects they often try to fit a lot of code to small boot sectors. They also very often put PMode initialization code so bugs are fixed very slow because each time boot sector update and bootstrap are needed. People also invent new formats of disk layout so that they can load and run something from their boot sector, although they can still use FAT12/16 as well as before. I really don't know why people make life more difficult than it is.

Why not to make a boot sector capable to load and run standard COM and EXE programs? You would have the only bootsector and it woudn't be changed each time when you changed something in the project. Why not to add there support for FAT and load a program regardless of place where it starts on the disk?

Do you like this idea? If so, check out my BootProg boot sector that does the job very well.

Current version (v1.2) of the boot sector is intended for use on standard diskettes that have FAT12 and primary DOS HDD partitions both FAT12 and FAT16. I tested it on the both FDD and HDD.

I hope you understand that programs loaded by the boot sector must not call MSDOS service functions. You may use BIOS services instead. - 50KB (NASM 0.98)

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OS Development for Dummies - OS Loader

A group of people that appear in the alt.os.development newsgroup have started a brand-new project called OS Development for Dummies. The OS Loader stands as a part of the project. It's a thing I've come up with. You may visit a site related to the project: Entire the project is held there and the OS Loader too. Newest version OS Loader is downloadable from here. If you wanna read the manual on the OS Loader, it's as simple as that. Just read it! :))

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Intel Manuals on x86 and x87

Intel 80386 Programmer's Reference Manual +
Detailed Instruction List (232 KB)

Intel 80386 Programmer's Reference Manual (in Russian) (216 KB)

Intel 80486 Programmer's Reference Manual (in Russian) (523 KB)

Intel 80387 Programmer's Reference Manual (121 KB)

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x86 Assembly Language Webring
This Site is Owned by: Alexei
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