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QP framework

NOTE: 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.

What's New?

View QP/C++ Revision History at: https://state-machine.com/qpcpp/history.html

About QP/C++

QP/C++ (Quantum Platform in C++) is a lightweight, open source software framework/RTOS for building reactive real-time embedded applications as systems of cooperating, event-driven active objects (actors). The QP/C++ framework is a member of a larger QP family consisting of QP/C, QP/C++, and QP-nano frameworks, which are all strictly quality controlled, thoroughly documented, and commercially licensable.

Safer Model of Concurrency

The QP framework family is based on the Active Object (actor) design pattern, which inherently supports and automatically enforces the following best practices of concurrent programming:

  • Keep data isolated and bound to active objects' threads. Threads should hide (encapsulate) their private data and other resources, and not share them with the rest of the system.

  • Communicate among active object threads asynchronously via event objects. Using asynchronous events keeps the threads running truly independently, without blocking on each other.

  • Active object threads should spend their lifetime responding to incoming events, so their mainline should consist of an event-loop that handles events one at a time (to completion), thus avoiding any concurrency hazards within an active object thread itself.

This architecture is generally safer, more responsive and easier to understand and maintain than the shared-state concurrency of a conventional RTOS. It also provides higher level of abstraction and the right abstractions to effectively apply modeling and code generation to deeply embedded real-time systems.

Hierarchical State Machines

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.

Built-in Real-Time 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, blocking QXK kernel that provides all the features you might expect from a traditional RTOS. Native QP ports and ready-to-use examples are provided for major CPUs, such as ARM Cortex-M (M0/M0+/M3/M4/M7).

Traditional RTOS/OS

QP/C++ can also work with a traditional RTOS, such as ThreadX, embOS, uC/OS-II and TI-RTOS, as well as with (embedded) Linux (POSIX) and Windows.


With 60,000 downloads a year, the QP family is the most popular such solution on the embedded software market. It provides a modern, reusable architecture for embedded applications, which combines the active-object model of concurrency with hierarchical state machines.

Getting Started with QP/C++

The following "Getting Started with QP/C++" guide provides step-by-step instructions on how to download, install, and get started with QP/C++ quickly: https://state-machine.com/doc/AN_Getting_Started_with_QPCpp.pdf

The guide also contains a tutorial, in which you build a simple "Blinky" application.

NOTE: QP/C++ can be unzipped anywhere in your file system, but the recommended location is C:\qp\qpcpp on Windows and ~/qp/qpcpp on Linux/MacOS.

QP/C++ Licensing

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.

NOTE: 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.

QP/C++ Documentation

The QP/C++ Manual is located online at: https://state-machine.com/qpcpp

How to get help?