Making your own Operating System: coding from Scratch

4 min readMay 23, 2024

Creating your own operating system (OS) is a challenging yet rewarding endeavor that allows you to understand the intricate details of how computers work at a fundamental level.

While developing a full-fledged operating system requires advanced knowledge of computer science and systems programming, creating a simple operating system kernel can be a great learning experience for aspiring software developers.

In this article, we’ll explore the basics of operating system development, step-by-step, and provide code snippets and examples to help you get started on creating your own operating system from scratch.

Understanding Operating System Development

An operating system is a software layer that manages hardware resources and provides services to user programs.

It controls the execution of programs, manages memory and storage, handles input and output operations, and provides a user interface.

Operating system development involves creating the core components of an OS, including the kernel, device drivers, and basic system utilities.

Key Components of an Operating System

1. Kernel

The kernel is the heart of an operating system, responsible for managing hardware resources, scheduling tasks, and providing essential services to user programs.

2. Device Drivers

Device drivers are software components that enable the operating system to communicate with hardware devices such as disks, network adapters, and input/output devices.

3. File System

The file system is responsible for organizing and managing files and directories on storage devices, such as hard drives and flash drives.

4. User Interface

The user interface allows users to interact with the operating system and execute commands or launch applications. It can be command-line based (CLI) or graphical (GUI).

5. System Utilities

System utilities are software tools that provide essential functionality, such as system configuration, file management, and network administration.

Building Your Own Operating System: Step-by-Step

Now let’s walk through the process of creating a simple operating system kernel using the x86 architecture as an example.

We’ll focus on the basics of kernel development, including bootstrapping, hardware initialization, and basic functionality implementation.

Step 1: Setting Up the Development Environment

To develop an operating system kernel, you’ll need a development environment with appropriate tools and resources.

You can set up a development environment using tools such as QEMU for emulation, a text editor for writing code, and a cross-compiler for compiling code for the target architecture.

Step 2: Bootstrapping

The bootstrapping process involves writing code that initializes the system and loads the kernel into memory.

This typically involves creating a bootloader, such as GRUB, that loads the kernel from disk and transfers control to it.

Step 3: Hardware Initialization

Once the kernel is loaded into memory, it needs to initialize hardware devices, such as the CPU, memory, interrupts, and peripherals.

This involves writing device drivers and low-level code to interact with hardware registers and controllers.

Step 4: Basic Functionality Implementation

After hardware initialization, you can start implementing basic kernel functionality, such as task scheduling, memory management, interrupt handling, and system calls.

This involves writing code to manage processes, allocate and deallocate memory, handle interrupts, and provide system services.

Step 5: Testing and Debugging

Testing and debugging are critical steps in operating system development. You’ll need to test your kernel on emulated hardware, such as QEMU, and debug any issues using tools like GDB and printing statements for logging.

Example Code Snippets

Bootloader (Assembly)

boot.asm
[BITS 16]
[ORG 0x7C00]
start:
mov ax, 0x07C0
add ax, 288
mov ss, ax
mov sp, 4096
mov ax, 0x07C0
mov ds, ax

Load kernel into memory

mov bx, kernel_start
mov ah, 0x02
mov al, 1
mov ch, 0
mov cl, 2
mov dh, 0
int 0x13

Jump to kernel

Photo by Nicholas Santoianni on Unsplash

jmp 0x0000:0x1000
kernel_start:

Kernel ©

// kernel.c
void kernel_main() {
// Main kernel code
while (1) {
// Kernel loop
}
}

Make File

all: kernel.bin
kernel.bin: boot.o kernel.o
ld -o kernel.bin -Ttext 0x1000 boot.o kernel.o - oformat binary
boot.o: boot.asm
nasm -f elf32 -o boot.o boot.asm
kernel.o: kernel.c
gcc -m32 -c -o kernel.o kernel.c

Clean

rm -f .o kernel.bin

Conclusion

Creating your own operating system is a challenging yet rewarding endeavor that allows you to gain a deep understanding of computer systems and software development.

By following the steps outlined in this article and experimenting with code snippets and examples, you can start building your own operating system kernel from scratch.

Whether you’re a beginner or an experienced developer, exploring operating system development can be an enlightening journey that enhances your programming skills and expands your understanding of computer science concepts.