Real-time operating system (RTOS) is an OS that guarantees a certain ability for a given time period. For example, it can be designed to show that an object has become available to the robot on the assembly line. Such shells are classified as “hard” and “soft”.
Hard operating systems in real time assume that the calculation cannot be performed if the object is not available in the appointed period (such an operation will fail).
In a soft operating system, in real time, the assembly line will continue to function under such conditions, but the production volume may be lower, since the objects are not able to be available at the appointed time, as a result of which the robot will be temporarily unproductive.
Before giving examples of real-time operating systems, you need to understand the features of their use. Some of these OSs are created for special applications, others - for a more general one. In addition, some general-purpose shells are also sometimes used for real-time operation. Well-known Windows 2000 or IBM Microsoft / 390 can serve as examples of this type of operating system . That is, even if the OS does not meet certain requirements, it may have characteristics that allow it to be considered as a solution for a specific application task in real time.
Examples of operating systems and their characteristics
In general, real-time operating systems have the following characteristics:
- Multitasking.
- Process flows that may be prioritized.
- A sufficient number of interrupt levels.
Real-time operating systems are often used as part of small embedded shells, which are used in the format of microdevices. So, some kernels can be considered as single-tasking operating systems (examples: kernels as part of iOS, Android, etc.) in real time. However, to perform their assigned tasks, other device components, such as drivers, are required. That is why a full-fledged real-time operating system, as a rule, is more than just a kernel.
A typical example of an RTOS application is an HDTV receiver and display. He must read the digital signal, decode it and display it as incoming data. Any delay will be noticeable as pixel video and / or distorted sound.
However, when the request sounds, “give examples of operating systems of this type”, the most famous names are meant to be mentioned. What is included in this group?
VxWorks by WindRiver
VxWorks is a real-time operating system developed as proprietary software using WindRiver. First released in 1987, VxWorks was originally designed for use in embedded systems that require real-time and deterministic performance. So, examples of operating systems of this type are used in the areas of security and safety, various industries (especially aerospace and defense), the production of medical devices, industrial equipment, robotics, energy, transport management, network infrastructure, and the improvement of automotive and consumer electronics.
VxWorks supports Intel (x86, including the new IntelQuarkSoC and x86-64), MIPS, PowerPC, SH-4, and ARM architecture. This RTOS comes with a powerful core, middleware, support for paid add-on packages and third-party hardware technologies. In its latest release, VxWorks 7, the system was upgraded for modularity and upgrade so that the OS kernel is kept separate from middleware, applications, and other packages.
QNX Neutrino
Also classic examples of operating systems of this type are some Unix-like shells. Such is the QNX Neutrino, originally developed in the early 1980s by the Canadian company Quantum Software Systems. Ultimately, the development was acquired by BlackBerry in 2010. QNX is one of the first commercially successful microkernel operating systems used in a variety of devices, including car and mobile phones.
FreeRTOS
FreeRTOS is a popular real-time nuclear OS for embedded devices that loads 35 microcontrollers. It is distributed under the GPL with an additional restriction and optional exceptions. The restriction prohibits benchmarking, while the exception allows users to use their own code together with closed source code, while preserving the kernel itself. This facilitates the use of FreeRTOS in native applications.
Windows CE
Windows Embedded Compact is a subfamily operating system developed by Microsoft as part of the Windows Embedded family of products. Unlike the Windows Embedded Standard, which is based on Windows NT, these operating system examples use an exclusive hybrid kernel. Microsoft provides Windows CE licenses for original equipment manufacturers who can modify and create their own user interfaces, providing the technical basis for this.