LightOS v0.2

A simple 32-bit hobby operating system for the x86 architecture, built from scratch for educational purposes.

About The Project

LightOS is a minimalist kernel and shell that demonstrates fundamental operating system concepts. It boots using GRUB, sets up its own stack, and provides a basic command-line interface that interacts directly with hardware (VGA text buffer and PS/2 keyboard polling).

The entire system is contained in a handful of files, making it easy to understand the boot process, kernel entry, and basic I/O handling.

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Features

LightOS includes a simple shell with a set of built-in commands:

• help: Displays the list of available commands.
• info: Shows system details like OS name, version, and architecture.
• clear: Clears the entire screen.
• echo [text]: Prints the provided text back to the console.
• uptime: Shows the (approximate) time since the system was booted.
• reboot: Restarts the computer by sending a command to the keyboard controller.
• calc [a+b]: A simple calculator that can add two single-digit numbers.
• colors: Displays a test pattern of all 16 available VGA text mode colors.

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Getting Started

Follow these instructions to build and run LightOS on your own machine.

Prerequisites

You will need a Linux environment with the following tools installed. On Debian/Ubuntu, you can install them with this command:

sudo apt-get update
sudo apt-get install build-essential nasm qemu-system-x86 grub-common grub-pc-bin

• make, gcc, ld: Core build tools.
• nasm: The Netwide Assembler, for boot.asm.
• qemu-system-i386: An emulator to run the operating system.
• grub-mkrescue: A tool to create a bootable ISO image.

Building To compile the kernel and create the bootable ISO, simply run make:

make

This will assemble boot.asm, compile kernel.c, link them into kernel.bin, and finally package everything into a bootable lightos.iso file.

Running The Makefile provides several targets to run LightOS in QEMU:

To run in a graphical window (recommended):

make run-gui

To run in your terminal (no graphics):

make run

(To exit QEMU in this mode, press Ctrl+A, then X)

Cleaning Up To remove all compiled object files and the ISO image, run:

make clean

Technical Details Architecture: 32-bit x86 (i386)

Bootloader: GRUB with a Multiboot v1 compliant header.

Kernel Entry: The boot.asm file sets up the Multiboot header, initializes the stack, and then calls the kernel_main function in kernel.c.

Screen Output: The kernel writes directly to the VGA text mode memory buffer at address 0xB8000.

Keyboard Input: The system uses polling (inb/outb) to read scancodes directly from the PS/2 keyboard controller ports (0x60 and 0x64). Interrupts are not used.

Project Structure lightos/ ├── boot.asm # Assembly entry point and Multiboot header ├── grub.cfg # GRUB bootloader configuration ├── kernel.c # Main C kernel, shell, and command logic ├── linker.ld # Linker script for memory layout ├── Makefile # Build automation script └── README.md # Project documentation

Generated after running 'make':

├── boot.o # Assembled boot object file ├── kernel.o # Compiled kernel object file ├── kernel.bin # Linked kernel binary └── lightos.iso # Final bootable ISO image