Real-time Systems

Real-time Systems

Real-time Systems: 

• It is another form of operating system which are used in environments where a large number of events mostly external to computer systems, must be accepted and processed in a short time or within certain deadlines. 
• Examples of such applications are flight control, real time simulations etc. Real time systems are also frequently used in military application.

• A primary objective of real-time system is to provide quick response times. User convenience and resource utilization are of secondary concern to real-dme system.
•  In the real-time system each process is assigned a certain level of priority according to the reletive importance of the even it processes.
•  The processor is normally allocated to the highest priority process among those which are ready to execute. 
• Higher priority process usually pre-emoted execution of lower priority processes. This form of scheduling called, priority based preemptive scheduling, is used by a majority of real-time systems.

Memory Management: 

• In real-time operating system there is a little swapping of program between primary and secondary memory. 
• Most of die time, processes remain in primary memory in order to provide quick response, therefore, memory management in real-time system is less demanding compared to other types of multi programming system. On the other hand, processes in real- time system tend to cooperate closely thus providing feature for both protection and sharing of memory.

I/O Management: 

• Time-critical device management is one of the main characteristics of real-time systems. It also provides sophisticated form of interrupt management and I/O buffering.

File Management: 

• The primary objective of file management in real-time systems is usually the speed of access rather than efficient utilization of secondary storage.Some embedded real-time systems does not have secondary memory. 
• However, where provided file management of real-time system must satisfy the same requirement as those found in time sharing and other multiprogramming systems.