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What is NitrOS-9?

NitrOS-9 is a real-time, process-based, multitasking, multi-user, Unix-like operating system for the 6809 and 6309 processors. It runs on TRS-80 Color Computer, Radio Shack Color Computer 2, Tandy Color Computer 3 and Dragon 64. The original OS-9 was created in 1979. NitrOS-9 is the modern equivalent of that OS, and includes advanced features like support for up to 2 MB RAM and 4 GB Hard drive partitions. It is still being developed, and support is available in many mailing lists and forums.

How do I run it?

The latest release can be found in the release folder. Development snapshot builds are performed from time to time, and can be downloaded as individual disk images or you can download the entire build in one (large) ZIP file.

If you are using a CoCo or Dragon emulator, then these disk images will run just fine.

If you are using a real CoCo, then you have two choices:

  1. Download the appropriate 40 or 80 track double sided disk images and use your PC to create physical floppies (requires a floppy system hooked to your CoCo and your PC).
  2. The best experience is to use the DriveWire 4 package. DriveWire lets your Mac, Windows, or Linux system act as a disk storage gateway for your CoCo, eliminating the need for floppy disks or hard drives being attached to your system. Using DriveWire 4, you can even link to the individual disk image of your choice over the Internet and boot your CoCo that way!


These are the official documents of the NitrOS-9 Project. They are ordered by the suggested reading order.

Getting Started with NitrOS-9 - This document is for those who are trying out NitrOS-9 for the first time.

The NitrOS-9 Windowing System - You can learn how to use the windowing system in NitrOS-9 Level 2 for the Color Computer 3 by reading this document.

NitrOS-9 Commands Reference - All of the standard NitrOS-9 commands are documented here.

NitrOS-9 Level 2 Development System

NitrOS-9 Technical Reference - If you want to learn how to write software under NitrOS-9, or are just curious about the technical aspects of the system, read this document.

Inside NitrOS-9 - a work in progress.

The NitrOS-9 Boot Process Explained - Details on how booting into NitrOS-9 works.

BASIC09 Programming Language Reference Manual

C Compiler User's Guide - Documentation for the Microware C Compiler.

CGFX Libary - The C Graphics Library created by Michael Sweet.

SuperDriver - SuperDriver is an RBF split-level architecture driver with lots of cool features and supports SCSI and IDE drives.

Helpful Information

Transferring DSK Images to Floppies - If you want to transfer disk images to real floppies using your PC, then read this.

Building NitrOS9 - NitrOS-9 can be built on any modern computer using cross-hosted tools. Read here to see how to set up your system to do this.

NitrOS-9 FAQ

What is NitrOS-9?
NitrOS-9 is an "OS-9 compatible" operating system for the TRS-80 Color Computer, Radio Shack Color Computer 2 and Tandy Color Computer 3. It is intended to replace both OS-9 Level One and OS-9 Level Two (once sold by Tandy through Radio Shack stores), as those products are no longer available, and have not been sold for years.
Is NitrOS-9 completely compatible with OS-9 for the Color Computer?
Yes, NitrOS-9 maintains compatibility with OS-9 Level One and OS-9 Level Two by using identical system calls and I/O handling. Existing utilities and applications developed for those operating systems should work fine under NitrOS-9.
I thought NitrOS-9 was only for the Tandy Color Computer 3 with a 6309 CPU. Is that true?
Historically, NitrOS-9 has been a 6309-only product. However, it has now been ported to the 6809 processor and supports Level 1 for the Color Computer. Since all Color Computers can now run NitrOS-9, the name was extended to cover all Color Computer platforms using either the 6309 or 6809.
How do I know which version of NitrOS-9 is for which Color Computer?
NitrOS-9 supports three "levels" and two processors, yielding six potential distributions:
  • NitrOS-9/6809 Level 1 for the Color Computer
  • NitrOS-9/6309 Level 1 for the Color Computer with a 6309
  • NitrOS-9/6809 Level 2 for the Color Computer 3
  • NitrOS-9/6309 Level 2 for the Color Computer 3 with a 6309
  • NitrOS-9/6809 Level 3 for the Color Computer 3
  • NitrOS-9/6309 Level 3 for the Color Computer 3 with a 6309
In short, Level 2 and Level 3 are exclusively for the Color Computer 3. Level 2 is compatible with OS-9 Level Two, and Level 3 contains additional features to manage system memory more efficiently.
Currently, NitrOS-9/6809 Level 1, NitrOS-9/6809 Level 2, and NitrOS-9/6309 Level 2 are available. The other distributions are still under development.
Is it legal to download and use NitrOS-9?
NitrOS-9 has been in existence since 1994, having been created by a number of dedicated individuals within the Color Computer community. Much of the code was written by the original NitrOS-9 team: Wes Gale, Bill Noble and Curtis Boyle. Later, Alan DeKok made even further improvements. Therefore, NitrOS-9 is an operating system created by the Color Computer Community, for the Color Computer Community.
How critical is it for me to use NitrOS-9? Can't I just stick with OS-9 Level One or Two?
There are two issues with OS-9 Level One or OS-9 Level Two today: first, there is no upgrade path for the products; second, neither operating system has been sold in Radio Shack stores for years, denying new users the ability to purchase valid licenses.
NitrOS-9 is today's and tomorrow's operating system for all Color Computers. It is constantly being improved and enhanced, is freely available, and is also faster and more optimized than Tandy's OS-9 operating systems.
Whatever happened to TuneUp for OS-9 Level Two?
That product is now superseded by NitrOS-9.
Can I download pre-built disk images?
Yes: from