Real-time system

Real-time system

· In a real time operating system, a job is to be completed within the rigid time constraints otherwise job loses its meaning.

· A real time system function correctly only if it returns the correct result within its time constraints

· Thus, in a real-time system, the correctness of the computation not only depends upon the logical correctness of the computation but also upon the time at which the result is produced.

Real-time system

In a real time system various functions like process scheduling, memory management, I/O management and file management are performed as follows :

1. Process scheduling . the real time system uses priority based pre-emptive scheduling. each process is assigned a certain level of priority and the process with the highest priority is allocated the processor among those which are in the ready state.

2. Memory management. In real time system, the processes remain in primary memory for most of the time in order to provide quick response.

3. I/O device management . time critical device management is main requirement of real time system . it also uses feature like interrupt management and I/O buffering.

4. File management. In real time system, file management does not aim at efficient utilisation of secondary storage rather main objective is to provide fast access.

single user operating system

2. Multi user operating system

3. Batch processing operating system

4. Multi programming operating system

5. Multi tasking operating system

6. Multiprocessing operating system

7. Time sharing operating system

8. Real time system

Real-time operating system are categorised into:

1. Hard real-time systems

2. Soft real-time systems

1. Hard real time systems complete the critical tasks within the definite interval of constraints. If the critical task is not completed within the time constraints then the hard real time system fails.

Thus, a hard real time system has to complete all the processes within definite deeding and a single miss leads to critical failure

2. Soft real time system are less restrictive in a nature and are not affected the lapse of time interval and do not cause any critical failure.

Soft real time system are used in the area of multimedia, virtual reality

Comparison between soft real time and hard real time system

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Change the priority of a process

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