QP/C++  5.8.1
About QP/C++™

What is it?

QP/C++™ (Quantum Platform in C++) is a lightweight, open source active object (actor) framework for building responsive and modular real-time embedded applications as systems of asynchronous event-driven active objects (actors). The QP/C++™ framework is a member of a larger family consisting of QP/C++, QP/C, and QP-nano frameworks, which are all strictly quality controlled, thoroughly documented, and available under dual licensing model.

The behavior of active objects is specified in QP/C++ by means of hierarchical state machines (UML statecharts). The framework supports manual coding of UML state machines in C++ as well as automatic code generation by means of the free QM™ modeling tool.

To use QP/C++™ effectively, you need to understand the key concepts that underline the architecture of the framework and your applications based on the framework.

What does it do?

The main goals of the QP/C++™ framework are:

  • to provide a reusable architecture based on active objects (actors), which is safer and easier to understand than "free-threading" with a traditional RTOS.
  • to provide a simple-to-use coding techniques for hierarchical state machines, with which to implement the behavior of active objects.
  • to provide efficient and thread-safe event-driven mechanisms for active objects to communicate, such as direct event passing and publish-subscribe.
  • to provide event-driven timing services (time events).
  • to provide a selection of built-in real-time kernels to run the QP applications, such as the cooperative QV kernel, the preemptive non-blocking QK kernel, and the preemptive blocking QXK kernel.
  • to provide testing support for applications based on software tracing (Q-Spy).
  • to provide portability layer and ready-to-use ports to 3rd-party RTOSes and desktop operating systems such as Linux and Windows.
  • to provide a target for modeling and automatic code generation from the QM modeling tool.

What's special about it?

The QP/C++™ framework is a unique offering on the embedded software market. It provides a modern, reusable architecture of embedded applications, which combines object-orientation with the particular model of concurrency, known as active objects (actors). This architecture is generally safer, more responsive and easier to understand than "free threading" with a traditional Real-Time Operating System (RTOS). It also provides high enough level of abstraction and the right abstractions to effectively apply modeling and code generation to deeply embedded systems.

Object Orientation

QP/C++™ is fundamentally an object-oriented framework, which means that the framework itself and your applications derived from the framework are fundamentally composed of classes and only classes can have state machines associated with them.


The most unique characteristic of the QP/C++™ framework is its very small footprint, especially in RAM. In this respect, QP/C++™ requires less resources than even the smallest conventional Real-Time Operating System (RTOS) kernel. At the same time, QP gives you a much higher level of abstraction than a conventional RTOS. With QP, you work at the level of active objects, state machines and events, as opposed to "naked" threads of an RTOS.

Hierarchical State Machines

The behavior of active objects is specified in QP by means of hierarchical state machines (UML statecharts). The frameworks support manual coding of UML state machines in C or C++ as well as fully automatic code generation by means of the free graphical QM™ modeling tool.

Built-in Kernels

The QP™/C++ framework can run on bare-metal single-chip microcontrollers, completely replacing a traditional RTOS. The framework contains a selection of built-in real-time kernels, such as the cooperative QV kernel, the preemptive non-blocking QK kernel, and the preemptive, dual-mode, blocking QXK kernel. The QXK kernel provides all the features you might expect from a traditional RTOS kernel and has been specifically designed for mixing event-driven active objects with traditional blocking code, such as commercial middleware (TCP/IP stacks, UDP stacks, embedded file systems, etc.) or legacy software. Native QP ports and ready-to-use examples are provided for major CPU families.


QP/C++ can also work with many traditional RTOSes and desktop OSes (such as Windows and Linux).

Popularity & Maturity

With over 15 years of continuous development and 60,000 downloads a year, the QP™ framework family is the most mature and popular such solution on the embedded software market.

The QP™ frameworks are used in millions of products worldwide in aerospace, medical devices, consumer electronics, wired and wireless telecommunications, industrial automation, transportation, robotics, and many more.


The book, Practical UML Statecharts in C/C++, 2nd Edition provides a detailed design study of the QP frameworks and explains all the related concepts.

Practical UML Statecharts in C/C++, 2nd Edition

How is it licensed?

QP/C++ is licensed under the increasingly popular dual licensing model, in which both the open source software distribution mechanism and traditional closed source software distribution models are combined.

If your company has a policy forbidding open source in your product, all QP frameworks can be licensed commercially, in which case you don't use any open source license and you do not violate your policy.

Open Source Projects

If you are developing and distributing open source applications under the GNU General Public License (GPL), as published by the Free Software Foundation, then you are free to use the Quantum Leaps software under the GPL version 3 of the License, or (at your option) any later version. Please note that GPL requires that all modifications to the original code as well as your application code (Derivative Works as defined in the Copyright Law) must also be released under the terms of the GPL open source license.

Closed Source Projects

If you are developing and distributing traditional closed source applications, you can purchase one of Quantum Leaps commercial licenses, which are specifically designed for users interested in retaining the proprietary status of their code. All Quantum Leaps commercial licenses expressly supersede the GPL open source license. This means that when you license Quantum Leaps software under a commercial license, you specifically do not use the software under the open source license and therefore you are not subject to any of its terms.

How to get help?

Please post any technical questions to the Free Support Forum hosted on SourceForge.net. Posts to this forum benefit the whole community and are typically answered the same day.

Direct Commercial Support is available to the commercial licensees. Every commercial license includes one year of Technical Support for the licensed software. The support term can be extended annually.

Training and consulting services are also available from Quantum Leaps. Please refer to the Contact web-page for more information.

Contact Information


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