{"id":5502,"date":"2021-03-06T04:23:01","date_gmt":"2021-03-06T04:23:01","guid":{"rendered":"http:\/\/fastbitlab.com\/?p=5502"},"modified":"2023-08-31T09:51:25","modified_gmt":"2023-08-31T04:21:25","slug":"freertos-lecture-1-what-is-real-time-application-rtas","status":"publish","type":"post","link":"https:\/\/fastbitlab.com\/blog\/freertos-lecture-1-what-is-real-time-application-rtas\/","title":{"rendered":"FreeRTOS Lecture 1 – What is Real Time Application (RTAs)?"},"content":{"rendered":"
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What is Real Time Application (RTAs)?<\/span><\/span><\/h1>\n
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Real-Time Applications<\/strong><\/span><\/p>\n

Truths and myths related to Real-Time Computing are as follows:<\/span><\/p>\n

1. <\/b>Myth:<\/span><\/span> Real-Time Computing is equivalent to fast computing.<\/span><\/p>\n

   Truth<\/span>: <\/b>Real-Time Computing is equivalent to predictable computing.<\/span><\/span><\/p>\n

2.Myth:<\/span> Real-Time Computing means higher performance.<\/span><\/p>\n

           Truth:<\/span><\/b> In Real-Time Computing, timeliness is more important than performance.<\/span><\/span><\/p>\n

What exactly mean by the word real-time, which is often used in the context of Real-Time Application (RTA)<\/strong><\/span> or Real-Time Operating System (RTOS)<\/a><\/strong>. <\/span><\/span><\/p>\n

The word real-time signifies that the application or the operating system deals with guarantees, not with raw speed. Whenever you say something is real-time, then timeliness is more important. That is, it promises to meet its deadline for a given timeline instead of just talking about raw speed.<\/span><\/p>\n

Application developers who think they need a real-time system for better performance of their application can actually get the performance they require by simply upgrading their hardware with faster processors, RAM, high-speed buses, etc. But that doesn\u2019t make a system real-time. <\/span><\/p>\n

A Real-Time System deals with guarantees, not with promises. If an application with limited hardware, and if it is able to meet a timeliness execution, then that system or application can be called real-time.<\/span><\/p>\n

A Real-Time System is one in which the correctness of the computations not only depends upon the logical correctness of the computation but also upon the time at which the result is produced. If the timing constraints are not met, system failure is said to have occurred.<\/span><\/p>\n

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For example, take a look at the graph shown in Figure 1. <\/span><\/p>\n

There the red line indicates that it is a Non-Real-Time Application, and the purple line indicates a real-time application. We have just plotted a graph of execution iterations vs. response time. <\/span><\/p>\n

Here you can see during multiple iterations, the execution time or the response time of a Real-Time Application is almost constant. It is roughly taking around, say, 2.5 seconds for every duration. So, its response time is fairly constant between multiple execution iterations. <\/span><\/p>\n

But take a look into the Non-Real-Time Application. Its response time is varying. For the first iteration, it took around 4 seconds, then for the next iteration, its response time was around 1.5 seconds, and for the next iteration, it took something around 2.5. The Non-Real-Time Application doesn\u2019t meet the timeliness behavior. So, you can\u2019t trust this application, isn\u2019t it? Because its response time is keeps on varying between multiple iterations. <\/span><\/p>\n

A Non-Real-Time Application will show this kind of behavior that its response time will always vary as time passes. But a Real-Time Application promises a fairly constant response time no matter in which constraints you execute that application. <\/span><\/p>\n

For example, one way of looking at this is that for a Non-Real-Time Application, you can speculate that the system load was high for the first iteration, so it took more time. <\/span><\/p>\n

For the next iteration, you can speculate that the system load may be less, that\u2019s why the Non-Real-Time Application got executed in less time, and for the last iteration, you can predict that the system load was again high. That\u2019s why this application took more time. But a Real-Time Application, no matter what the system load is, it will always take the same response time between multiple execution iterations. This is the meaning of real-time, which is used in the context of Real-Time Application or Real-Time Operating System.<\/span><\/p>\n

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Figure 1. Graph.<\/span><\/figcaption><\/figure>\n

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What are Real Time Applications (RTAs)?<\/strong><\/span><\/p>\n