What does "real time" mean?

 

These days, "real time" is a commonly used term. Despite being a technical term, it is frequently used in everyday speech. When I say, "I do not watch much real-time TV," I'm implying that I use streaming services to watch the shows I want to watch at the times I want. Therefore, "immediate" or "occurring now" are colloquial terms for "real time." For instance, how does this fit with its exact definition when we talk about a real-time operating system? …

A rather outdated computer dictionary's definition of "real-time system" is as follows:

 “Any system in which the processing of data input to the system to obtain a result occurs virtually simultaneously with the event generating that data.”

It uses airline reservation systems as an example. It is obvious that this definition does not meet our needs.

Here is a better definition:

“A real-time system is one in which the accuracy of the calculations is dependent on both the computation's logical correctness and the result's time of generation. System failure is considered to have occurred if the system's timing constraints are not fulfilled.”

Another way of putting this definition is to say that a real time system is, above all, predictable. We tend to use the term deterministic.

Therefore, a deterministic operating system allows a programmer to create programs with the same feature by carrying out all of its operations inside a precisely defined timescale. Real time means quick [or maybe slow] enough for the particular needs of the application at hand, not fast.

 

It's not quite that clear-cut, unfortunately. A degree of determinism in an operating system is possible; it concerns the variation in the time required to complete tasks under various conditions. Thus, a traditional real-time operating system is very deterministic due to its extremely low variation. Linux, on the other hand, is typically extremely variable and might not be considered real-time.

When creating a system, there is always the "brute force" method, in which you design with enough raw CPU power that the OS's speed and variance barely matter because everything will be finished on time. That might be a good answer for some requirements, but such wasteful resource utilization is not a choice for many.

At Silicon Signals, we specialize in designing real-time systems tailored to your application's unique requirements. Whether you need a highly deterministic RTOS for precise operations or a resource-efficient solution that ensures timely execution without over-engineering, we can help. From optimizing Linux for real-time performance to developing custom RTOS-based applications, our expertise bridges the gap between theory and application.