🪐 NanoOS v3.0

An educational, bare-metal 32-bit operating system built completely from scratch using NASM x86 Assembly (no C, no external libraries!). It boots directly from a custom Stage 1 bootloader on a virtual floppy, switches to 32-bit Protected Mode, sets up GDT and IDT, configures isolated task stacks for a cooperative multitasking kernel, and drops the user into an interactive shell with custom utilities, file browser, and games.

👥 Developers

• Hanan (Lead Kernel & Graphics Developer)
• Ahmed (Lead Shell & App Systems Developer)

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🚀 Key Features

• Custom Bootloader (Stage 1): Formatted as a 512-byte MBR boot sector. Sets up Real Mode segments, loads kernel sectors using BIOS interrupt INT 0x13, and transitions to 32-bit Protected Mode.
• Stable Multitasking Kernel: Handles isolated kernel and user shell task stacks (preventing stack overflows) and operates cooperative context switching (sys_yield via timer tick/software calls).
• Interrupt Descriptor Table (IDT): Correctly remaps Programmable Interrupt Controllers (PICs) and implements custom ISRs and IRQ handlers (specifically IRQ0 for Timer and IRQ1 for Keyboard).
• Hardware Keyboard Pipeline: Captures raw PS/2 and Serial input, manages active modifier shift-states, and implements safe backspacing/screen rendering.
• Interactive Shell: Robust, case-insensitive parser with argument support. Features over 30 commands, including:
  • System: help, about (credits screen), clear / cls, ver, time/date (via CMOS RTC), uptime, mem, regs (displays active registers), ps (task list).
  • Filesystem: Simulated commands ls, cd, pwd, mkdir, rmdir, touch, rm, cat, cp, mv, files (graphical file browser).
  • Apps & Games: calc (arithmetic parser), game (number guessing), snake (interactive WASD terminal game), fibonacci sequence, prime checker, tictactoe (two-player local game), morse translator, sysinfo, wc (word count), hex converter, bootanim (animated boot sequence), play (retro PC speaker music), paint (interactive pixel canvas), and clock (large digital clock).

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🛠️ Requirements & Setup

Prerequisites

• Windows (Powershell) or WSL (Linux shell).
• NASM (x86 Assembler) in your System PATH.
• QEMU (x86 Emulator) installed to test the OS.

Building and Running

1. Clone the repository:

   git clone https://github.com/Muhammad-Ahmed-CTRL/NanoOS-v3.git
   cd NanoOS-v3

2. Run the build script using PowerShell to assemble the binaries and create the nanoos.img floppy image:

   .\build.ps1

3. Best way to run natively on Windows (with Sound enabled!):

   & "C:\Program Files\qemu\qemu-system-i386.exe" -fda c:\Users\muham\Downloads\NanoOS\NanoOS\nanoos.img -boot a -m 4M -name "NanoOS v3.0" -audiodev dsound,id=snd0 -machine pc,pcspk-audiodev=snd0 2>&1

   (Alternatively, use .\build.ps1 run to launch via WSL).

Making it Bootable on Real Hardware

When you run .\build.ps1, it generates three boot images:

• nanoos.img - 1.44 MB floppy image for QEMU/virtual floppy boot.
• nanoos.iso - El Torito CD/floppy-emulation image for virtual CD boot.
• nanoos-usb.img - raw USB-HDD image for real USB flash drives.

1. To run it on a real laptop/PC:
   • Download a tool like Rufus.
   • Select your USB drive, and choose the generated nanoos-usb.img file.
   • Flash it in raw/DD mode if Rufus asks.
   • Boot it with Legacy BIOS / CSM enabled. NanoOS is BIOS-only and does not include a UEFI bootloader, so UEFI-only laptops will not list it as a bootable USB.
2. To run it in VirtualBox or VMware:
   • Create a new virtual machine.
   • Mount the nanoos.iso file into the virtual CD/DVD drive.
   • Start the VM, and NanoOS will boot instantly!
3. To clean up build artifacts:

   .\build.ps1 clean

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📸 Screenshots

Fresh QEMU-verified screenshots after the latest visual cleanup:

USB-HDD Boot	Idle Restore

Giant Clock	Text Paint

The shell redraws cleanly after the idle animation, and fullscreen apps restore the footer/prompt correctly when exiting.

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🎓 Academic Context

This operating system was built as a semester project for the Computer Organization and Assembly Language (COAL) course at Air University Islamabad. It demonstrates low-level hardware interaction, CPU architectures, memory segmentations, registers, and system level software without relying on modern high-level operating systems.

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🏷️ Core Concepts & Search Keywords

For developers and students researching low-level systems or the Air University COAL Project, this repository provides a reference implementation of:

• Bare-metal x86 Assembly OS Dev: Built from scratch using NASM, without C or external standard libraries.
• Custom 512-byte MBR Bootloader: Handles 16-bit Real Mode segmenting, sector loading via BIOS INT 0x13, A20 gate activation, and transitioning to 32-bit Protected Mode.
• Interrupt Descriptor Table (IDT) & ISRs: Re-mapping 8259 PICs, configuring custom ISRs, and managing hardware interrupts (Timer IRQ0 and Keyboard IRQ1).
• Cooperative Multitasking Kernel: Task-state stacking, cooperatively switching context (sys_yield), and safe stack isolation to prevent buffer overflows.
• VGA Text Mode & Graphic Applications: Direct video memory writing (0xB8000), a graphical text-mode file browser, real-time keyboard pixel canvas drawing, and console-based games.