In my first semester of college, we had a subject called Computer Architecture, where we studied the legendary 8085 microprocessor. That’s when I got my first taste of assembly language.
At first, honestly? I thought it was a total waste of time outdated, overly complex, and not really “practical” in today’s tech world.
But fast forward to the end of my second semester, and there I was:
building my own simple OS using assembly language.
Okay, calling it an “OS” might be a stretch — it’s more like the “Hello, World!” of operating systems. But still, I made a bootable image that runs in QEMU. It clears the screen, positions the cursor, and prints a custom message. All from scratch, in raw x86 assembly. No Linux, no BIOS hacks, no GRUB — just main.asm and a lot of patience.
⚙️ Tools I Used
- NASM (Netwide Assembler): to write and compile the Assembly code
- QEMU: a lightweight emulator to test my OS without frying my hardware
- dd (Disk Destroyer, jokingly): to write the compiled image to a file
- Makefile (optional): to automate the build steps
- Linux Terminal: to assemble, run, and debug everything
💡 What This Mini-OS Does
- Boots directly from BIOS — no OS beneath it
- Switches to text mode
- Positions the cursor on screen using BIOS interrupts
- Prints two strings:
A custom message like "Hello, World!"
A fun signature — “Booted with love ;)”
- That’s it. No file system, no multitasking, no kernel — just a raw, handcrafted bootloader that talks to the screen like it’s 1981 again.
🧰 What I Learned
How real computers boot — not from Linux, not from Windows, but from raw machine code
BIOS interrupts and video memory
The importance of that magical 0xAA55 at the end of every bootable sector
How little it takes to make something feel big — this project was less than 512 bytes
🌱 Why I’ll Never Forget This
It’s easy to overlook low-level concepts when we’re surrounded by modern abstractions. But building something that talks directly to the CPU — with no libraries, no OS, no safety nets — taught me respect for how machines really work.
It also made me realize: every great operating system — even the big names — probably started as a “Hello World” moment like this.
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