The TetOS Project

Kimi wa jitsu ni baka dana!

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Contents

1. Overview
2. Progress
3. Building
4. Contributing
5. Legalities
6. Licence
7. Acknowledgements

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Overview

The TetOS Project is an open-source kernel and bootloader - soon to be a full operating system.

The kernel is written in:

• Zig
• Assembly

The bootloader is written in:

• Zig
• Assembly

The build system is written in:

• Zig
• Nim
• Shell (Bash)

Made for the UTAUloid and chimera Kasane Teto. It aims to bring new meaning to what a operating system can be, inspired by Terry Davis' TempleOS

Project artifacts:

• TetoEFI (bootx64.efi)

TetoEFI is the bootloader for the TetOS project

• KasaneKernel (kasanekernel)

KasaneKernel is the kernel for the TetOS project

TetOS only plans to support x86_64 desktop computers currently, and only supports building on a x86_64 GNU/Linux machine, but this may change in the future. (Other types of systems may work but will not be tested)

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Progress

The current progress of TetOS is as follows:

• TetoEFI started
• KasaneKernel started

TetoEFI

• Program functional

• UEFI intergration

  • BootService

    • Boot service handling
    • Exit boot service support

  • SimpleTextOutput

    • Stdout console
    • Stderr console
    • Hardware resetting
    • Device modesetting
    • Console geometry

  • SimpleTextInput

    • Stdin console
    • Hardware resetting
    • Device modesetting
    • Unicode input support
    • Scancode input support

  • GraphicsOutput

    • Block transfer
    • Location-based block transfer
    • Hardware resetting
    • Device modesetting
    • Screen painting
    • Animation refresh/loop

  • SerialIo

    • QEMU stdio serial support
    • Hardware resetting

• Filesystem

  • Read
  • Write
  • Directory
  • Metadata
  • 4GB+ support

• Kernel loading

  • Memory mapping
  • Boot cmdline passing
  • Jumping into execution

KasaneKernel

• Program functional

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Building

The following are instructions and explainations of the TetOS build system and how to build a TetOS image

• None currently. The build system tetostrap is still in development.
• Any attempts to compile shall be done by naviagting to src and running zig build
• Then, to run in QEMU, go to the project root and run ./run.sh

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Contributing

You are intrested in developing for the TetOS Project?

Please see CONTRIBUTING.md for infomation

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Legalities

The TetOS Project may include or display copyrighted content inspired by 3rd-party works, such as the character Kasane Teto. These works remain property of their respective copyright holders. The TetOS Project's authors or contributors do not claim ownership of such content.

This project is purely fan-made and is in no way associated with TWINDRILL or Crypton Future Media, Inc.

For information regarding Kasane Teto’s usage, licensing, and permissions, please see the official guideline: Kasane Teto CTU. The PCL license applies mutatis mutandis to these elements.

All original code, design and resources created specifically for TetOS are licenced under LICENSE, for details and possible exceptions - see below.

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Licence

Copyright (C) 2025-2026 Taylor Johnson (Wakana Kisarazu / Tayzonxperia).

All rights reserved.

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version

For the licence the TetOS Project is under, see LICENCE and for full details about copyright, see COPYING

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Acknowledgements

For licences of other software that may be under a different licence to the TetOS Project licence, see Licences

• EDK2 OVMF Firmware - (Licence) - For the OVMF firmware required to run TetOS in a virtual machine.