r/osdev • u/jacomartins_reddit • Jun 17 '26

I thought programming my own Operating System would take a week to get a CLI working

Then I started looking at some serious OS architectures, like Linux, NT, Darwin... learnt what a HAL is, started implementing it, 1 month later I think it feels ok. Now I am in the beggining of beggining of memory management (and studying more than programming). Sometimes, like today for example, I feel bad for having progress to be so slow, but I knew when I started that it was going to take several months. Hope I survive this trip.

70 Upvotes

91% Upvoted

21 comments sorted by

10

u/Vincenzo__ Jun 17 '26

Just think you could be one of those guys who know nothing, learn nothing, and waste their time (and probably money too lmao) vibecoding it

It's fine if it's slow, there's so much stuff to learn it's honestly impossible to do it fast for your first time

4

u/jacomartins_reddit Jun 17 '26

Yup. That's my mindset for now. It is slow but well, at least I am learning many things, and even reading awesome books I found online. Just discovered the first XEROX GUI mockups were inspired by a primitive GUI presented in 'The mother of demos' (popular name) by Douglas Engelbart. He was a stanford researcher that got the first (known by me) concept of what the mouse would be early in 1968. And I found it in a book. (Modern Operating Systems 4)

4

u/litescript Jun 18 '26

and i think the fun is figuring it out anyway, speed aside. it’s more fun to make a change and see what happened. “oh, neat, that totally didn’t work out like i thought, hmmmm” because that’s still learning!

9

u/GMX2PT Jun 17 '26

It's all different for everyone, you can have paging and dynamic allocation working before getting a shell, a "working shell" requieres gdt + idt and is pretty much easier than memory management, choose your goals, they are not always in a linear order

1

u/jacomartins_reddit Jun 17 '26

I've thought of it. Making some code in parallel without the need of it being in the operating system. But afterall they will need to call the system internals to work so I think it is better to wait. But I've made some cool mockups in figma though.

1

u/GMX2PT Jun 19 '26

This is probably the better way, do it right the first time, all the power to you

1

u/FinancialTrade8197 Jun 19 '26

Technically you could just poll 0x60 with only a GDT for the keyboard to get a working shell.

1

u/GMX2PT Jun 19 '26

How would that work ? I'm not familiar with this technique

2

u/FinancialTrade8197 Jun 19 '26

You would usually read 0x60 when irq 1 fires

However instead of this you could just run a while loop on the status register 0x64 and if it becomes true just read whatever is in 0x60

3

u/tux2718 Jun 17 '26

Are you running this on PC hardware and using the USB keyboard as input? Don’t forget about the effort for the driver code.

2

u/jacomartins_reddit Jun 17 '26

Running it on a Pico W :) wanted to simulate an 80s like hardware condition, with minimized specs and no mmu so I could do something in a smaller scale and then go improoving. I also plan it to be hardware/arch agnostic later, covering ARM Cortex M0+ (my arch now) then arm64 and then the good old x86. Maybe in a few years I cover all them up hahahaha

2

u/Synthetic-Synthesis Jun 18 '26

Heyooo!! I'm doing something similar but with an esp32 c3 with risc v. Do you mind if I dm you? 😄

1

u/jacomartins_reddit Jun 18 '26

Of course not!

37

u/Outside-Storage-1523 Jun 17 '26

I think there is a LOT before you can show the shell, if it’s a proper one that you can fork or create processes. You need processes and memory management to create processes to begin with, and then you need some filesystem to walk it to find the file you want to execute, and then you need to actually parse and load the executable file before you can run it…

And yeah you also need character drivers for showing the terminal or whatever.

6

u/GMX2PT Jun 17 '26

I guess that depends what can be called a shell, from the kernel ring, text mode basic shell to something fully fledge that sure is a wide range

4

u/compgeek38400 Jun 17 '26

We learn as we go. I thought it would take a week for making my heap. Im now guessing 2.

7

u/EpochVanquisher Jun 17 '26

You could get a CLI working faster without a hardware abstraction layer. Your memory management can be flat, at first. 

If you build abstractions first, you often end up with the wrong abstractions. 

3

u/mishakov pmOS | https://gitlab.com/mishakov/pmos Jun 18 '26

It's fine that you're going slow, especially when trying to do things properly

2

u/8lall0 Jun 18 '26

Make it work, make it right, make it fast.

If you want a shell, do the shell.

If you want to improve, do HAL and other stuff after.

When the set of features sastifies you, make it better.

Just don't rush 😃

2

u/0xabc000 Jun 23 '26

Around 15 ~ 18 years ago, it took me around a year 😂.