VenomOS 𝐕🕷️🕸️

VenomOS is a 64-bit educational operating system built from scratch using Assembly (NASM) and Modern C++. It features a custom BIOS bootloader, Long Mode support, a freestanding kernel, interrupt handling, PS/2 keyboard driver, VGA terminal, interactive shell, and a built-in Snake game.

Made possible by BassemMohamed

A 64-bit educational operating system built completely from scratch using Assembly and Modern C++.

No external operating system libraries.
No GRUB.
No Limine.
No UEFI Framework.

Everything boots directly from BIOS.

Screenshots

Booting

VenomOS

Commands

Snake

Features

• Custom Stage 1 Bootloader
• Custom Stage 2 Bootloader
• BIOS Disk Loading
• A20 Line Enable
• Global Descriptor Table (GDT)
• Protected Mode Transition
• Long Mode (64-bit)
• Custom Linker Script
• Freestanding C++17 Kernel
• VGA Text Terminal
• Interrupt Descriptor Table (IDT)
• Hardware Interrupt Handling
• PS/2 Keyboard Driver
• Interactive Command Shell
• Built-in Snake Game
• Fully bootable disk image
• QEMU Ready

---

Boot Process

BIOS
 │
 ▼
Stage 1 Bootloader
 │
 ▼
Stage 2 Bootloader
 │
 ├── Enable A20
 ├── Load GDT
 ├── Switch to Protected Mode
 ├── Setup Paging
 ├── Enter Long Mode
 │
 ▼
64-bit Kernel
 │
 ▼
Drivers
 │
 ▼
Interactive Shell

---

Project Structure

VenomOS
│
├── boot/
│   ├── stage1.asm
│   ├── stage2.asm
│   ├── disk.asm
│   ├── gdt.asm
│   ├── a20.asm
│   └── print.asm
│
├── kernel/
│   ├── kernel.cpp
│   ├── kernel_entry.asm
│   ├── linker.ld
│   ├── interrupts.*
│   ├── keyboard.*
│   ├── shell.*
│   ├── snake.*
│   └── vga.*
│
├── include/
│
├── build/
│
└── Makefile

---

Components

Bootloader

The bootloader is divided into two stages.

Stage 1

Responsible for:

• Initial BIOS startup
• Disk access
• Loading Stage 2
• Boot validation

---

Stage 2

Responsible for:

• Enabling the A20 line
• Loading the Global Descriptor Table
• Switching to Protected Mode
• Configuring Long Mode
• Loading the 64-bit kernel
• Jumping into C++ code

---

Kernel

The kernel is written in freestanding C++17.

Current responsibilities include:

• Kernel initialization
• Terminal setup
• Driver initialization
• Interrupt initialization
• Launching the interactive shell

---

Keyboard Driver

Features:

• PS/2 keyboard support
• Interrupt driven input
• Character translation
• Shell integration
• Snake game controls

---

VGA Driver

The VGA subsystem provides:

• Colored text output
• Cursor management
• Screen clearing
• Formatted terminal output

---

Interrupt System

Implemented features include:

• Interrupt Descriptor Table (IDT)
• Assembly interrupt stubs
• C++ interrupt handlers
• Keyboard IRQ handling
• Timer support

---

Shell

The operating system includes a simple interactive shell.

Current commands:

Command	Description
help	Show available commands
clear	Clear the screen
version	Show OS version
whoami	Display current user
snake	Launch Snake game

---

Snake Game

A simple built-in Snake implementation demonstrates:

• Real-time keyboard input
• Screen rendering
• Game loop
• Collision detection
• Integration with the kernel shell

---

Build Requirements

• NASM
• x86_64-elf GCC Toolchain
• x86_64-elf LD
• GNU Make
• QEMU

---

Build

make

---

Run

make run

---

Technologies

• NASM Assembly
• C++17
• Freestanding Environment
• Custom Linker Script
• BIOS Boot
• x86_64 Architecture
• QEMU

---

Current Status

Implemented:

• Bootloader
• Long Mode
• Kernel
• VGA
• Keyboard
• Interrupts
• Shell
• Snake

Planned:

• Physical Memory Manager
• Heap Allocator
• Virtual Memory Manager
• FAT File System
• ATA Driver
• Process Scheduler
• Multitasking
• User Mode
• ELF Loader
• System Calls

---

Purpose

VenomOS is an educational operating system project created to explore low-level software development, operating system internals, bootloaders, CPU architecture, memory management, interrupt handling, and kernel programming from scratch.

---

License

MIT License

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Made with Bassem Mohamed using Assembly and Modern C++