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A2osX Multi-Tasking OS for Apple II

Updated May 24, 2020

A2osX 0.94

If you would like to see more screen shots of A2osX click here.


A2osX is an operating, programming and execution environment for the 128K Enhanced Apple //e and Apple //gs series of computers. While layered atop of ProDOS, taking advantage of all ProDOS block devices and MLI calls; A2osX is much more than an application or command shell. Written in 65C02 assembly for speed of execution and efficient memory management; A2osX is a multitasking and yes multi-user development environment bringing many of today's server operating system features to our venerable vintage 8-bit systems.

The foundation of A2osX enabling its multi-user multitasking capabilities is a reusable set of APIs and LIBs (written in Assembly) that all programs can and do use which make them very lean and fast. For instance, there is one network API that any program can call which in turn handles the I/O to different brands of LAN cards via a set of drivers. In addition, multiple programs can be using the network at the same time such as the TELNETD server and the TELNET client. A key benefit is that code for each program is smaller because the network API is doing a great deal of the work. With CORE APIs like printf and LIBs such as Network loaded only once (much like a DLL in Windows) memory is conserved, providing more resources to support your A2osX programs.


A2osX is designed to work on any 128k Enhanced Apple //e or newer computer. Specifically, A2osX relies on the enhanced instruction set found in the 65C02 processor (this includes the 65C816 found in the //GS). A2osX will not run on an Apple ][ or ][+, a non enhanced //e or on systems without at least 128K of memory. A2osX does not require any special hardware cards, but does support and its operation can be enhanced with the presence of a mass storage devices (any ProDOS block device), a network card, Super Serial Card and/or a Time Card.

Consult the documentation section below to find other resources available to you for learning how to install, use, develop and test A2osX. The Hardware section of the User Guide contains more information on tested and supported hardware.


KansasFest 2021

The A2osX team is proud to present "A2osX and the Languages of Development," a virtual KansasFest 2021 presentation by Patrick Kloepfer, which you can find here.

Upcoming Release - 0.94 Stable Alpha

The A2osX Team is preparing to issue the first Stable Alpha of A2osX Version 0.94. This new version will include an updated version of ProDOS FX, further kernel enhancements to improve memory usage and for the first time an included Assembler so developers can edit, assemble and test problems all from with A2osX. We are inviting interested developers and testers to join us on Slack!

If you would like to read all the past news articles for A2osX, you can read the news article found here.

Visit us at A2osX

This is just a place holder and plug for our A2osX internet site. Stay tuned here for news about this site. We have created a Page to discuss A2osX on Facebook and have a new Twitter handle to test new A2osX features which will soon be used as a messaging channel, so please follow. We have created a new forum for discussing A2osX, features, examples, use cases, etc. It can be found on Google Groups.

Disk images

You can use and/or install A2osX from the media in our Media directory found here. Provided media includes Release, RC (Release Candidate), Stable and Bleed (Cutting Edge) editions in 140K, 800K and 32MB images. Please consult our Media Guide for more information.


The A2osX team is pleased to report that great strides have been made in terms of documentation. While much of it is in draft form, there is a new Users Guide, Developers Guide, Shell Developers Guide, Technical Spec and Command Guide. Work continues to expand and enhance the documentation for A2osX. While still under construction, it is provided to you to bring you as much information about A2osX as quickly as possible. We happily welcome any help and contributions from others to this or any area of the A2osX project. The repository all A2osX documentation can be found here. This directory includes the system generated specifications for all the A2osX APIs as well as all our other documentation.

Technical Documentation

There are two types of Technical Documentation available. First there is the Automatically Generated Documentation that is created from the source code of A2osX. These documents capture all the internal A2osX APIs and system calls available to the A2osX programmer. Developers should scan through these documents before beginning any A2osX project. In addition, please make sure you look at the programming template file that is the best start to any A2osX program; it can be found here.

In addition, there is the developer generated Technical Specifications that document the internal and external A2osX commands, utilities and shell language. The master technical spec file can be found here.

How You Can Help

The A2osX Team welcomes your help in making this the best operating environment for the Apple 2! Specifically, the more users who can test the most current RELEASE, CANDIDATE or STABLE media on their unique hardware and report back their findings, the better A2osX becomes. In additions, comments on, suggestions, or contributions to our documentation are greatly appreciated. Lastly, A2osX would not be what it is without our great core development team. We could certainly use more developers, especially in Assembly (S-C Assembler familiar even better) to contribute new utilities, applications and features for A2osX.

Join us on Slack!

We are inviting interested developers and testers to please join our A2osX Slack channel to get release announcements, learn more about new features, get support and provide feedback. An invite to our Slack channel can be found here.


A2osX is licensed under the GNU General Public License.

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.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.

The full A2osX license can be found Here.

Copyright 2015 - 2020, Remy Gibert and the A2osX contributors.