Have you ever wondered exactly what happens between pressing the power button and your desktop appearing on the screen?
For most software developers, the operating system is a black box. We write code, compile it, and the OS magically handles the memory, CPU scheduling, and hardware interactions. But what if you could peel back the layers of abstraction? What if you could write the very software that rules the hardware?
Building an operating system is widely considered the ultimate rite of passage for a programmer. It’s challenging, deeply technical, and incredibly rewarding.
That’s why I am thrilled to announce my upcoming blog series: Building an Operating System From Scratch, which will be available exclusively to my supporters!
What to Expect in This Series
In this step-by-step tutorial series, we aren’t just going to look at theory—we are going to write code. We will start with a blank screen and slowly build up a functional, custom kernel capable of interacting with hardware and communicating over a network.
Whether you are a computer science student, a low-level programming enthusiast, or just a curious web developer looking to understand how the metal actually works, this series is for you.
Exclusive for Buy me a Coffee members!
Join for as low as $2/month and get access to this series and other exclusive member-only posts!
Here is the roadmap of what we will cover:
1. How Computers Boot
Before we can write an OS, we need to understand how the hardware wakes up. We’ll explore the legacy BIOS, UEFI, and the exact sequence of events that kicks off the boot process.
2. Multiboot Explained
Why write a bootloader from scratch when we can stand on the shoulders of giants? We’ll dive into the Multiboot specification, which allows standard bootloaders like GRUB to load our custom OS seamlessly.
3. Writing a Kernel Entry Point
Where does C meet Assembly? We’ll write the very first lines of code that execute after the bootloader hands over control to our kernel.
4. Cross Compilers for OS Dev
You can’t just use your system’s default compiler to build an OS. We will set up a dedicated cross-compiler toolchain (GCC/Binutils) to ensure our code is compiled for bare metal, independent of our host system.
5. Bootstrapping a Kernel
We’ll explore the precise steps required to transition from the raw, initial boot state into a fully functioning higher-level language environment (like C or C++).
6. Linker Scripts Explained
How does the computer know where the code, data, and stack belong in memory? We’ll demystify linker scripts (.ld files) and take absolute control over our binary’s memory layout.
7. VGA Output Without an OS
It’s time for the ultimate “Hello, World!”. We’ll write directly to the VGA text mode memory buffer to print colored text to the screen—with zero reliance on external libraries or existing operating systems.
8. Running the Kernel in QEMU
Rebooting a physical machine every time you compile is painful. We will set up QEMU, a powerful hardware emulator, to rapidly test and debug our OS in an isolated virtual machine.
9. Kernel Memory Layout
Memory management is the heart of any OS. We’ll take a high-level look at how a kernel structures its memory, laying the groundwork for paging, segmentation, and heap allocation.
10. Networking in a Custom OS
The holy grail of hobbyist operating systems. Once our kernel is stable, we’ll tackle the monumental task of writing basic network drivers and protocols to get our custom OS talking to the outside world.
Are You Ready to Hack the Mainframe?
Building an OS isn’t quick, and it isn’t always easy, but the “Aha!” moments you’ll experience are unparalleled. By the end of this series, the black box of computer architecture will be wide open.
Prerequisites: You’ll need a basic understanding of C, a foundational grasp of how memory works (pointers are your friends!), and a healthy dose of curiosity.
Exclusive Access: This entire series will be available exclusively to my Buy Me a Coffee members! Join now for as low as $2/month and get lots of benefits and exclusive content.
Get your code editors ready. The first post, How Computers Boot, drops this week. Let’s build something incredible.
Have a specific OS feature you want to see covered later in the series? Let me know in the comments below!
