Different types of Operating Systems and Real-time OS

They are those operating systems in which each task performs its function within prescribed deadlines and failure to these deadlines may cause severe consequences.


This article explains the real-time operating system and its types.


It is defined as the system in which the correctness of computations depends on logical correctness and the time in which the result is produced. 

  • It has strict time constraints.
  • Processing must be done within the defined constraints or the system will fail.
  • User convenience and resource utilization are secondary concerns.
  • Examples: Scientific experiments, medical imaging systems, industrial control systems, weapon systems, robots, air traffic control systems, etc.
  • It is of two types:

Hard time operating system

  • It guarantees the on-time completion of critical tasks.’
  • It has autonomous error detection.
  • It has limited utility for rollback/recovery due to the short-term integrity of data.
  • Data file sizes are small/medium
  • In this system, virtual memory is almost never found.

Soft real-time operating system

  • A critical real-time task gets priority over other tasks and retains the priority until it completes.
  • It has user addicted error detection.
  • It has the long-term integrity of data.
  • Data file sizes are large.

Examples: Multimedia, virtual reality, advanced scientific projects like undersea exploration, and planetary overset.


  • It gives more output while using all the resources and keeping all devices active.
  • It needs only around 5 microseconds to shift the task.
  • It focuses on applications that are running and gives less importance to the applications in the waiting stage of the life cycle.
  • RTOS can be used in embedded systems like in transport because of the small size of the program.
  • RTOS is error-free so it has no chance of errors in performing tasks.
  • RTOS can be used for any application which runs 24*7 because it does less task shifting and gives maximum output.
  • It manages memory allocation nicely.


  • Uses heavy system resources.
  • Low multitasking 
  • Complex algorithm
  • Device drivers and interrupt signals
  • Thread priority
  • Expensive 
  • Not easy to program
  • Low priority tasks get no time to run. 


The real-time operating system is used in cases when rigid time requirements have been placed on the operation of a processor. It contains well-defined and fixed time constraints.

Special thanks to Ami Jangid for contributing to this article on takeUforward. If you also wish to share your knowledge with the takeUforward fam, please check out this article