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The Object-Oriented State Machine Operating System

  1. Draw a hierarchical state machine.

  2. Run the OOSMOS code generator to generate C code into an OOSMOS object.

  3. Compile

  4. Run

Key Features

  • Accepts hierarchical state machines drawn using the open source UML drawing package UMLet.

  • Generates object-oriented C code from UMLet drawings. Generated code is concise and easy to read.

  • Powerful state thread feature gives you an instant thread of execution within each state.

  • Dual Licenses

    • Open Source -- GPLv2
    • Commercial open source license without the GPLv2 restrictions. Note: Code generator source code available to commercial licensees only.
  • Superior event management:

    • Event codes are managed locally within each object's class.
    • Events support argument passing.
    • Events are delivered in a Publish/Subscribe fashion.
    • Each object has its own event queue (if the object uses events).
  • Supports orthogonal regions (also known as "and" states).

  • OOSMOS's simple object structure promotes superior object-oriented encapsulation and information hiding.

  • Very small footprint. Core code is comprised of only oosmos.h and oosmos.c which, together, are under 1700 cloc.

  • Portable c99 code runs on Windows, Linux, ST Micro, Arduino, ESP32, PIC32, and more.

  • A core set of OOSMOS classes, such as pin (GPIO), sw (switch), btn (button) and toggle provided.

  • Many time management capabilities and APIs.

  • Extremely fast, constant-time memory allocation scheme, ideal for DO-178B/C.

  • Code fully LINT'd using PC-LINT. An oosmos-user.lnt file is provided to allow you to cleanly lint your code that uses OOSMOS.

Initial Set Up

Once you've cloned OOSMOS, some of the example directories for embedded devices may be incomplete. In order to fully populate the Examples directories, you must first run the Python script while in the top-level directory.


  • Report bugs and feature requests here on GitHub.