The Main Concept of a Programming Model

The main concept of a programming model is to give guidelines for programmers on how to design and how to structure the software. Usually there are two different ways in IoT operating systems, either to build it as an event-driven or as a multi-threaded system. In an event-driven system all of the processing starts after it has been triggered by an external event. Usually this needs to be done by using interrupt calls. This model is useful when you want your system to be efficient in terms of memory. Multithreading on the other side means there are multiple threads that are processing tasks. This point of view gives more time for CPU to work efficiently and therefore saves energy consumption. Furthermore, the programming model can also be either synchronous or asynchronous.

The main difference between these two options is that in the synchronous model one task is executed at a time and in the asynchronous model tasks can be paused of executing and a thread can start executing some other task meanwhile. Basically asynchronous programming provides better usage for a system because there is no need to wait for the task to be finished before moving to another one. An important point to consider when comparing operating systems is the way input and output is handled. Unlike full-fledged operating systems there are different possibilities for gaining input and transferring data. Most common devices such as printers, displays and keyboards are usually not used and supported in IoT environments. But what all kinds of systems have in common and probably the most obvious input/output is network connectivity. Therefore, it is necessary to analyze the different options on how the network stack may be implemented and which network protocols are used.

Further implementations including several layers are for instance ZigBee, Wireless ANT and 6LoWPAN.newline Apart from the network access there are usually sensors used to gain input from the environment. Typical measures in Wireless Sensor Networks (WSN) are temperature, humidity, touch, force, sound, light and magnetic fields. Therefore, it is important to compare in which ways operating systems interact with sensors/transducers and actuators and which types they support and APIs they use. Because network connectivity and sensors provoke high power consumption we will consider the use of energy within this topic as well. Another important consideration is whether the system is POSIX compliant for ensuring compatibility between the OS and applications that will run on top of it.begin{figure}includegraphics[width=250pt]{myOSIgraphic.JPG}