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A Real Time Operating System is a software component that rapidly switches between tasks, giving the impression that multiple programs are being executed at the same time on a single processing core.

 Eg: PSOS, VRTX, RT Linux, Lynx, etc
TYPES OF REAL TIME OPERATING SYSTEM

 There are 3 types of real time operating systems:-


1. SOFT REAL TIME OS

Soft real time OS is a type of OS where certain deadlines may be missed but they will respond at a time t=0+.
Soft real time systems are not constrained to extreme rules. The critical time of the soft real time may be delayed to some extent. The expected latency between the tasks and time constraints may be deviated. The preemption period for a soft real time task is about few milliseconds.
Eg: Digital camera, mobile phones, online data base etc

2. HARD REAL TIME OS

Hard real time OS is a type of OS we can predict the deadline but they will respond at a time t=0. Hard real time systems are constrained to predicted time constraints, deadlines and latency. The preemption period for hard real time system is almost less than few microseconds.

 Eg: Air bag control in cars, anti-lock brake, engine control system etc.

3. FIRM REAL TIME OS

This Firm real time OS has certain time constraints which are not strict and it may cause undesired effect. Its based on a system that is a time critical system where most of the tasks are completed in time so that most of the deadly events are reduced.
Eg: Manufacturing systems with robot assembly lines.
OPERATING SYSTEM vs REAL TIME OPERATING SYSTEM




NEED FOR REAL TIME OPERATING SYSTEM

The benefits of using a Real Time Operating System include:-

  • Priority Based Scheduling: The ability to separate critical processing from non-critical is a powerful tool.
  • Abstracting Timing Information: The RTOS is responsible for timing and provides API functions. This allows for cleaner (and smaller) application code.
  • Maintainability/Extensibility: Abstracting timing dependencies and task based design results in fewer interdependencies between modules. This makes for easier maintenance.
  • Modularity: The task based API naturally encourages modular development as a task will typically have a clearly defined role.
  • Promotes Team Development: The task-based system allows separate designers/teams to work independently on their parts of the project.
  • Easier Testing: Modular task based development allows for modular task based testing.
  • Code Reuse: Another benefit of modularity is that similar applications on similar platforms will inevitably lead to the development of a library of standard tasks.
  • Improved Efficiency: An RTOS can be entirely event driven; no processing time is wasted polling for events that have not occurred.
  • Idle Processing: Background or idle processing is performed in the idle task. This ensures that things such as CPU load measurement, background CRC checking etc will not affect the main processing.






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