Work vector created by stories —freepik.com

This article is part of a series of articles explaining the development of an x86 Operating System. You can find all of the previous articles at the end.

So far we have an operating system with a kernel that has interrupt, memory segmentation, paging, and a kernel heap. But we are yet to enable support for user-space applications. This is why in this article we are finally entering User Mode.

Since we already have everything we need to enable user mode, it might seem easy to implement User Mode. But trust me, it can be a headache if we make…


Process vector created by stories — from freepik

This article is part of a series of articles explaining the development of an x86 Operating System. You can find all of the previous articles at the end.

In my last article, I explained about organizing memory in an Operating System using Paging. You can go back to that article to know all about integrating a simple paging setup into the memory, using this link below.

But we didn’t stop there. We took our OS to the next level by relocating the kernel to 3 GB in the virtual address space. …


This article is part of a series of articles explaining the development of an x86 Operating System. You can find all of the previous articles at the end.

In one of my previous articles, I explained something called Memory Segmentation. If you seem confused you can go back to that article to know all about integrating segmentation into the memory.

Work vector created by stories — freepik

This article will contain a way to organize memory as well; called Paging. Now you might be thinking, “Didn’t we already organized the memory of our OS two articles ago? Why do we need to mess with that again?”

So…


vector created by vectorjuice — freepik

This is the first article on introducing User Modes in a series of articles explaining the development of an x86 Operating System. It can be used as a stand-alone guide but it will make a lot more sense if you follow the series from the beginning. If you are all caught up, we can move along to our next big step in OS development.

So far we have managed to boot our Operating System, have it read input from the keyboard, and display the output. Let’s see what else we can make our OS do.

What if we can make…


Banner vector created by katemangostar — freepik.com

In one of my previous articles, I explained how to display text on the console and how to write data to the serial port. If you seem confused you can go back to that article to catch up.

So since we have taught our OS to produce output it would be quite nice if it also knows how to read input. So let’s start with the most common source of input; the keyboard. So how does the keyboard work? You just press a button and, voilà, it’s printed on the screen! Is it that simple? …


People vector created by pch.vector — freepik.com

This article is part of a series of articles explaining the development of an x86 Operating System. It can be used as a stand-alone guide but it will make a lot more sense if you follow the series from the beginning. If you are all caught up, we can move along to our next step in OS development.

So far we have only been working in real mode, which limits us to 1MB of RAM. Since this isn’t nearly enough to do anything useful, we need to make the jump into protected mode, which will allow us to access the…


If you have ever installed any software onto your computer, you definitely have come across a foot-long terms and conditions document that you had to agree to. Any sane person, including myself, doesn’t give this a second thought and just clicks “I agree” to get on with the installation. (To be completely honest, I didn’t even fully read the license I myself made for my own app.)

But you wouldn’t just sign some shady contract given by a stranger? Would you?

That is why it is crucial for anyone agreeing to these licenses to understand the basics of software licenses…


This is the third article in a series of articles explaining the development of an x86 Operating System step-by-step. If you seem lost I recommend going back to my first article.

In this article, I will explain how to display text on the console and how to write data to the serial port. We do this by creating a driver. A driver is a code that acts as a layer between the kernel and the hardware, providing a higher abstraction than communicating directly with the hardware.

First, let’s start by creating a drive for the frame buffer to display text…


GIF of a designer sitting at their desk while scrolling past various designs which are holographic.

Imagine you worked really hard in designing an app. You prototyped your first design and implemented the core functionalities. In your eyes, it’s the most perfectly designed application. Then someone comes along and tells you that it is garbage and they will never use it.

So how do you make sure that your design appeals to other people? You would need to evaluate it — but how?


This is the second article in a series of articles explaining the development of an x86 Operating System step-by-step. In the previous article, I explained how to implement the smallest possible OS that can be used together with GRUB. The only thing possible with that OS was to write 0xCAFEBABE to the eax register. If you seem lost I recommend going back to this article below.

This article will explain how to use C instead of assembly code as the programming language for the OS. Although using assembly gives us the maximum control over every aspect of the code and…

Hasini Samarathunga

Software Engineering Undergraduate

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