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Thursday, April 25, 2013

What is the difference between Hard and Soft real-time systems?

- Real time operating systems are the systems that have been developed for serving to the real time requests of the applications. 
- They are readily capable of processing the data as it is inputted. 
- They do not make any delays in buffering. 
- Thus, the time taken for processing is quite less.
- The scheduling algorithms used by the real time operating systems are quite advance and dedicate themselves to a small set of applications. 
- Minimal thread switching latency and interrupt latency are two key factors of these kinds of operating systems. 
- For these systems the amount of time they take for responding matters more than amount of work they do.
These systems are used to maintaining consistency in producing the output. 

The real – time operating systems can be divided in to two categories namely:
  1. The hard – real time operating system and
  2. The soft – real time operating system
In this article we discuss about these two systems and the common differences between them.
  1. The hard real time operating systems produce less jitter while producing the desired outputs. On the other hand, the jitter produced by the soft real time operating system is quite more when compared to its hard real time counterpart.
  2. The thing that distinguishes them is not the main goal but rather the type of performance it gathers i.e., whether hard or soft.
  3. The soft real time operating systems have been designed as such that they can usually meet the deadlines whereas, the hard real time operating systems are designed in such a way so as to meet the deadlines deterministic-ally.
  4. The hard – real time systems are also called as the immediate real time systems. They are bound to work within the confined strict deadlines. If in case, the application is unable to complete its task in the allotted time, then it is said to have failed. Some examples of the hard – real time operating systems are: anti-lock brakes, aircraft control systems and the pacemakers.
  5. Hard real time operating system are bound to adhere to the deadlines assigned to them. Missing a deadline can incur a great loss. As for the soft real time operating systems, it is acceptable if the deadline is missed such as in the case of the online databases.
There is also a third category of the real – time operating systems that is not so known. It is called the ‘firm RTOS’. They also need to keep up to the deadline since missing it won’t cause any catastrophic effect but may give results that are undesirable.

More about Real time Operating System

- The embedded systems have evolved all of a sudden and now they are present all around us in digital homes, cell phones, air conditioners, cars and so on. 
- We very rarely recognize the extent to which they have eased our day to day life. 
- Safety is another aspect of our lives for which we depend on these embedded systems. 
- The thing that controls these systems is the operating systems. 
- Real time operating system is what that is used by most of these gadgets. 
- The tasks that are assigned to a real – time OS always have deadlines. 
- The OS adheres to this while completing it. 
- If these systems miss the deadline the results can be very dangerous and even catastrophic. 
- With each passing day the complexity of these systems is increasing and so our dependence on them.
- Some examples of real – time operating systems are:
Ø  RTLinux
Ø  Windows CE
Ø  LynxOS
Ø  VxWorks
- The RTOS know well not to compromise with the deadlines. 

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