Home
QNX Software Development Platform
QNX SDP is a cross-compiling and debugging environment, including an IDE and command-line tools, for building binary images and programs for target boards running the QNX OS 8.0.
System Architecture
The System Architecture guide accompanies the QNX OS and is intended for both application developers and end-users.
The Philosophy of the QNX OS
The primary goal of the QNX OS is to deliver the open systems POSIX API in a robust, scalable form suitable for a wide range of systems—from tiny, resource-constrained embedded systems to high-end distributed computing environments. The OS supports several processor families, including x86 and ARM.
Interprocess communication
When several threads run concurrently, as in typical realtime multitasking environments, the OS must provide mechanisms to allow them to communicate with each other. Interprocess communication (IPC) is the key to designing an application as a set of cooperating processes in which each process handles one well-defined part of the whole.
QNX OS as a message-passing operating system
QNX OS was the first commercial operating system of its kind to make use of message passing as the fundamental means of IPC. The OS owes much of its power, simplicity, and elegance to the complete integration of the message-passing method throughout the entire system.

QNX Momentics IDE User's Guide
This User's Guide describes version 8.0 of the Integrated Development Environment (IDE) that's part of the QNX Tool Suite.
QNX Software Development Platform
QNX SDP is a cross-compiling and debugging environment, including an IDE and command-line tools, for building binary images and programs for target boards running the QNX OS 8.0.
- Quickstart Guide
- System Architecture
  The System Architecture guide accompanies the QNX OS and is intended for both application developers and end-users.
  - The Philosophy of the QNX OS
    The primary goal of the QNX OS is to deliver the open systems POSIX API in a robust, scalable form suitable for a wide range of systems—from tiny, resource-constrained embedded systems to high-end distributed computing environments. The OS supports several processor families, including x86 and ARM.
    - An embeddable POSIX OS?
      According to a prevailing myth, if you scratch a POSIX operating system, you'll find UNIX beneath the surface! A POSIX OS is therefore too large and unsuitable for embedded systems.
    - Product scaling
      Since you can readily scale a microkernel OS simply by including or omitting the particular processes that provide the functionality required, you can use a single microkernel OS for a much wider range of purposes than you can a realtime executive.
    - Why POSIX for embedded systems?
      A common problem with realtime application development is that each realtime OS tends to come with its own proprietary API. In the absence of industry standards, this isn't an unusual state for a competitive marketplace to evolve into, since surveys of the realtime marketplace regularly show heavy use of in-house proprietary operating systems. POSIX represents a chance to unify this marketplace.
    - Why QNX OS for embedded systems?
      The main responsibility of an operating system is to manage a computer's resources. All activities in the system—scheduling application programs, writing files to disk, sending data across a network, and so on—should function together as seamlessly and transparently as possible.
    - Microkernel architecture
      Buzzwords often fall in and out of fashion. Vendors tend to enthusiastically apply the buzzwords of the day to their products, whether the terms actually fit or not.
    - Interprocess communication
      When several threads run concurrently, as in typical realtime multitasking environments, the OS must provide mechanisms to allow them to communicate with each other. Interprocess communication (IPC) is the key to designing an application as a set of cooperating processes in which each process handles one well-defined part of the whole.
      - QNX OS as a message-passing operating system
        QNX OS was the first commercial operating system of its kind to make use of message passing as the fundamental means of IPC. The OS owes much of its power, simplicity, and elegance to the complete integration of the message-passing method throughout the entire system.
  - The QNX OS Microkernel
    The microkernel implements the core POSIX features used in embedded realtime systems, along with the fundamental QNX OS message-passing services.
  - Interprocess Communication (IPC)
    Interprocess Communication (IPC) plays a fundamental role in the transformation of the microkernel from an embedded realtime kernel into a full-scale POSIX operating system. As various service-providing processes are added to the microkernel, IPC is the glue that connects those components into a cohesive whole.
  - The Microkernel Instrumentation
    The microkernel (procnto-smp-instr) is equipped with a sophisticated tracing and profiling mechanism that lets you monitor your system's execution in real time. This instrumentation works on both single-CPU and SMP systems.
  - Process Manager
    The Process Manager can create and manage multiple POSIX processes, each of which may contain multiple POSIX threads.
  - Dynamic Linking
    In a typical system, a number of programs will be running. Each program relies on a number of functions, some of which will be standard C library functions, like printf(), malloc(), write(), etc.
  - Resource Managers
    To give the QNX OS a great degree of flexibility, to minimize the runtime memory requirements of the final system, and to cope with the wide variety of devices that may be found in a custom embedded system, the OS allows user-written processes to act as resource managers that can be started and stopped dynamically.
  - Filesystems
    The QNX OS provides a rich variety of filesystems. Like most service-providing processes in the OS, these filesystems execute outside the kernel; applications use them by communicating via messages generated by the shared-library implementation of the POSIX API.
  - Character I/O
    A key requirement of any realtime operating system is high-performance character I/O.
  - Networking Architecture
    As with other service-providing processes in the QNX OS, the networking services execute outside the kernel. Developers are presented with a single unified interface, regardless of the configuration and number of networks involved.
  - TCP/IP Networking
    Our TCP/IP stack is included in the io-sock networking stack and uses the common FreeBSD API.
  - High Availability
    The term High Availability (HA) is commonly used in telecommunications and other industries to describe a system's ability to remain up and running without interruption for extended periods of time.
  - What is Real Time and Why Do I Need It?
    Real time is an often misunderstood—and misapplied—property of operating systems. This appendix provides a summary of some of the critical elements of realtime computing and discusses a few design considerations and benefits.
  - Glossary
- OS Components & Operations
- Graphics
- Programming
- System Security Guide
  The QNX System Security Guide is intended for both system integrators who are responsible for the security of a QNX OS system and developers who want to create a QNX OS resource manager free from vulnerabilities.
- Utilities & Libraries
- Migrating to QNX OS 8.0
QNX Software in the Cloud
QNX Software in the Cloud enables developers to use the QNX OS in the Amazon cloud environment.
QNX Toolkit for Visual Studio Code
This User's Guide describes the QNX^® Toolkit for Visual Studio Code. The guide introduces you to the QNX Toolkit by explaining the QNX development environment and how to build, run, and debug your QNX^® Operating System (OS) applications and systems.
QNX Hypervisor User's Guide
This User's Guide explains the QNX hypervisor architecture and provides instructions for installing and running a QNX Hypervisor system, changing system components and configuration, and using hypervisor features such as virtual devices (vdevs).
Typographical Conventions, Support, and Licensing
This section describes the typographical conventions used throughout the documentation, explains how to obtain technical support, and provides some information about licensing.

QNX OS as a message-passing operating system

QNX SDP8.0System ArchitectureDeveloperUser

QNX OS was the first commercial operating system of its kind to make use of message passing as the fundamental means of IPC. The OS owes much of its power, simplicity, and elegance to the complete integration of the message-passing method throughout the entire system.

In QNX OS, a message is a parcel of bytes passed from one process to another. The OS attaches no special meaning to the content of a message—the data in a message has meaning for the sender of the message and for its receiver, but for no one else.

Message passing not only allows processes to pass data to each other, but also provides a means of synchronizing the execution of several processes. As they send, receive, and reply to messages, processes undergo various changes of state that affect when, and for how long, they may run. Knowing their states and priorities, the microkernel can schedule all processes as efficiently as possible to make the most of available CPU resources. This single, consistent method—message-passing—is thus constantly operative throughout the entire system.

Realtime and other mission-critical applications generally require a dependable form of IPC, because the processes that make up such applications are so strongly interrelated. The discipline imposed by QNX OS's message-passing design helps bring order and greater reliability to applications.

Page updated: March 05, 2025