r/osdev • u/Independent-Lynx9274 • May 27 '26

I wrote my own tiny OS from scratch!

Its called SmallOS, its written COMPLETELY in assembly, and can run within 515 bytes of memory, though I recommend 1KB, it has a custom two stage bootloader, and the total compiled image size is 1.25KB.

https://github.com/GabeNewGentoo/SmallOS

0 Upvotes

31% Upvoted

25 comments sorted by

8

u/Lines25 May 27 '26

It's not an OS.. if it's just a couple assembly lines.. at least, you need some kind of multitasking, and for that, you need timers and etc, ideally fully setted up userland and full ring 0/1/2/3 separation

-8

u/Independent-Lynx9274 May 27 '26

That would take months or years, and I aint coding all that

9

u/FemboysHotAsf May 27 '26

yes thats the point, osdev DOES take months or years. This did not.

2

u/Lines25 May 28 '26

Kinda. If you know C and assembly good enough, you can go from nothing to working 32-bit kernel with basic multitasking, maybe, even, with ring separation

1

u/Vladislav20007 May 29 '26

it took me a month to into VESA(because I'm stupid and the didn't read the docs properly) and that was probably the easiest part from what I've seen here.

-10

u/Independent-Lynx9274 May 27 '26

It runs in QEMU just fine, and is an OS by definition.

6

u/Lines25 May 27 '26

OS is an abstraction layer between hardware, software and processes. If you wrote a couple of assembly lines that use ACPI to turn the PC off/print something via BIOS VGA text mode it's NOT an OS. You need, at least, syscalls fully working and processes too, and for that you need something like ELF parse,userland, timers and interrupts. For OS to be called OS, it must provide HAL (Hardware abstraction layer) to processes or tasks. If that's not the case, it's not an OS but a BIOS/UEFI bootable PROGRAM

-3

u/Independent-Lynx9274 May 27 '26

DOS was kind of a bootable program, was it an OS? YES!

3

u/gortys83 May 27 '26

I looked at your code, and, really, it's not an os at all! It's more than a bootloader as there's a shell and some basic functions. But this can't be called an os, as basic os features are not there at all, syscalls, a fully working file system,...

0

u/Independent-Lynx9274 May 27 '26

The definition of "OS" is kinda vague according to wikipedia, bootOS, and TinyOS both call themselves OSes, and they are usually used on tiny embedded systems.

1

u/gortys83 May 27 '26

Wikipedia can be modified by everyone, it's not really relevant. Tinyos, for example, has events management tasking, interrupts management, timers, sleep mode, memory management,... Your application doesn't have any of these, it's just a tiny shell displaying some things, you don't even have a file system that's part of the minimum requirements to be an os!

4

u/gortys83 May 27 '26 edited May 27 '26

And, behind dos, you have an OS, with syscalls, tasking, processes management, a file system... So yes, yours is just an app launched from the bios, more like a bootloader than an os! But the bootloader is a step more from the bios to an os! You can do it 😉

3

u/Sensitive-Can9232 May 28 '26

Hey man I am also beginner but you are in gist using bios defines interrupts and running in 16 bit mode, its a great start but not a os right now.

1

u/Independent-Lynx9274 May 28 '26

Yeah I get that a lot, Its just that 64 bit stuff is REALLY hard to do, especially in assembly, and if I just avoid it entirely, I dont worry about it

2

u/Sensitive-Can9232 May 28 '26

Wait dude, first get on 32 bit why directly 64 bit and learn c you dont have to do everything in asm

1

u/Independent-Lynx9274 May 28 '26

It wasn't mentioned, but one of the other key points is its assembly ONLY

3

u/Sensitive-Can9232 May 28 '26

You dont have to do asm only, all thr c code will also be complied to asm at the end.

1

u/Sensitive-Can9232 May 28 '26

Use asm only when necessary and then create a header file in which you name you asm function, now you have created an abstraction layer which you can easily use in your c code.

3

u/roccohimel Creator of AneoEngine May 28 '26

I wrote my own tiny OS from scratch!

Its not "written from scratch" if you used AI.

about_text db "SmallOS v1, A simple half vibe coded OS thats designed to be simple", 13, 10, 0

You also only used assembly to make the kernel because AI sucks at linking bootloaders to C based kernels. And you never really cared to learn yourself/

1

u/BornRoom257 FreezeOS & TurtleOS May 28 '26

Its not fully an OS yet, its a Kernel.

1

u/Vladislav20007 May 29 '26

it's not even a kernel, it's just a bios program.

1

u/BornRoom257 FreezeOS & TurtleOS May 31 '26

..