A custom 32-bit operating system written in C and Assembly.
Boots from an ISO or FAT and runs as a raw binary.
Intentionally built without modern security constraints to encourage deep low-level learning, experimentation, and hacking.
As of now, atOS includes shell, TUI and GUI libraries, assembler/dissasembler, and multitasking support.
atOS is a from-scratch 32-bit x86 operating system crafted in C and Assembly. The project is geared toward systems programmers, students, and OS enthusiasts who want to explore how operating systems work at the hardware/software boundary.
Unlike modern operating systems, atOS removes safety restrictions, giving developers complete control and transparency into memory, hardware, and execution.
This makes atOS ideal for learning, experimentation, and low-level programming without the abstractions and protections of contemporary OSes.
TL;DR: atOS is a simple, open-source 32-bit Ring0 operating system designed for educational purposes and low-level exploration.
- 🖥️ 32-bit x86 Architecture — runs on legacy and virtualized hardware.
- 🛠️ Assembler and dissasembler (Compiler WIP) — integrated experimental assembler and disassembler for low-level programming.
- 🔓 No Safety Barriers — Ring 0, no protection layers or user/kernel enforcement, making it ideal for exploration.
- 🗄️ File System Support — ISO9660 for CD-ROM images and FAT32 for local storage.
- 🖥️ Graphics & UI — VBE-based graphics with custom ATGL and ATUI libraries. Examples are SANDBOX.BIN, PAINT.BIN and JOT.BIN
- 🧩 Modular Driver Stack — support for RTL8139 (Ethernet), AC97 (Audio), PS/2 (Keyboard/Mouse), Serial ports and more!
- 🐢 Multitasking — simple cooperative scheduler for handling multiple processes.
- 🐚 Shell Environment — a feature-rich command-line shell with environment variables and BATSH shell language for scripting.
- 🎮 System Programs — suite of utilities including
ASTRAC (compiler),PAINT,CLOCK,JOT (text editor), and games likePONG. - 📖 Open Source — licensed under MIT, designed as a learning tool for systems programming.
You can run atOS from the provided ISO in a virtual machine.
QEMU is the recommended environment, others aren't guaranteed to work.
| Resource | Recommended |
|---|---|
| RAM | 1024 MB |
| CPU | 1 Core |
| HDD | over 256 MB |
sudo apt install qemu-system-x86Download from the official QEMU website and follow the installation instructions, or use WSL with the Linux instructions above.
# Creates a hard disk image.
qemu-img create -f raw hdd.img 256M
# Creates folder for the debug.log
mkdir -p OUTPUT/DEBUG
# Creates your hard disk image
qemu-img create -f raw hdd.img 256M
# Runs the ISO file
qemu-system-i386 -vga std \
-m 1024 \
-boot order=d \
-cdrom $(OUTPUT_ISO_DIR)/$(ISO_NAME) \
-drive id=cdrom,file=$(OUTPUT_ISO_DIR)/$(ISO_NAME),format=raw,if=none \
-drive id=hd0,file=hdd.img,format=raw,if=none \
-device piix3-ide,id=ide \
-device ide-hd,drive=hd0,bus=ide.0 \
-device ide-cd,drive=cdrom,bus=ide.1 \
-device ac97,audiodev=snd0 \
-debugcon file:OUTPUT/DEBUG/debug.log \
-global isa-debugcon.iobase=0xe9 \
-audiodev sdl,id=snd0 \
-nic user,model=rtl8139,mac=52:54:00:12:34:56 \Want to dig into the source or contribute? Here’s how to set up the environment.
Install the essential build tools:
# For Debian/Ubuntu
sudo apt install qemu-system-x86 nasm make gcc genisoimage cmake ninja-buildTools used in development:
| Tool | Version | Purpose |
|---|---|---|
| QEMU | 8.2.2 | Virtualization and testing |
| NASM | 2.16 | Assembler for x86 assembly code |
| Make | 4.3 | Build automation |
| GCC | 13.3.0 | C compiler for building tools and libraries |
| Genisoimage | 1.1.11 | Create ISO images for booting |
| CMake | 3.28.3 | Build system generator for libraries and tools |
| Ninja | 1.11.1 | Fast build system |
The project uses make with simple targets:
-
Show all available commands:
make help -
Build and launch atOS:
make iso run
CMake is used for processes and libraries
Debugging support is minimal.
Please see DOCS/DEBUGGING.md for options and tips. QEMU writes a debug log to:
OUTPUT/DEBUG/debug.log(port 0xE9 debugcon)
Use SOURCE/STD/DEBUG.h or SOURCE/KERNEL/32RTOSKRNL/DEBUG/KDEBUG.h
Planned and in-progress features for atOS:
- ATUI & ATGL UI/Graphics Libraries
- BATSH Scripting Language
- Text Editor (JOT)
- Dynamic Library Loading
- Assembler / Disassembler
- C Compiler implementation
- Improved ACPI & Power Management
- Network Stack refinement (TCP/IP)
This roadmap is tentative and may evolve as the project grows.
Additional documentation is located in the DOCS/ folder, as well as inline within source directories and headers and in README files found inside each directory!
This project is licensed under the MIT License. See the LICENSE file for details.
- CREDITS file for a full list of credits and acknowledgments.