Real Time Operating System (RTOS), Examples, Applications, Functions

Real Time Operating System (RTOS), Examples, Applications, Functions

What is Real Time Operating System (RTOS)

Definition – Here, we will explain real time operating system. Now RTOS is stands for “Real time operating system”, and it is also known as embedded operating system. Real time operating system is totally depending upon the clock interrupts. This system produces the Interrupt Service Routine (ISR) interrupts. RTOS implemented the Priority system for executing all types of process. Entire RTOS is synchronized with the process, and they can make communication in between all process.

Block Diagram of Real Time Operating System 

real time operating system

ROM (Read Only Memory) chip is used for storing the RTOS because this chip is capable to store data in long life.

Types of Real Time Operating System (RTOS)

There are three types of Real time O/S, describe below each one.

Soft Real Time

Soft Real Time O/S allows few delay with using this operating system, but in this SRT (Soft Real Time) O/S defines the deadline to particular jobs (tasks). In this system, do not allow delay in large amount of time, so due to that mechanism their deadlines are managed by the Soft Real Time O/S.

Examples are: Cameras, smart phones, data management, online transaction, online bid in stock exchange etc.

Firm Real Time

In Firm Real Time O/S accepts the more deadline rules. so occurrences of the missing deadlines are not getting more impact but could be show some unpredictable outputs, and due to that can be reduced the quality of all products.

Some examples are: Automation system in the industry sector like as visual inspection, Multimedia products.

Hard Real Time

In the Hard Real Time, all feeding tasks must be begun to execute on predefined scheduling time, and their given all tasks must be done within allotted time duration. So due to that in this RTOS, all deadlines are managed with strictly.

Examples: Automobile control system like as Anti Lock & Air Bag, Airline Control System, Diagnosis Control System,     

Components of Real Time Operating System (RTOS)

  • Scheduler
  • Synchronization mechanism
  • Memory Management
  • Function Library
  • Interrupt Service Mechanism
  • I/O Management
  • Fast dispatch latency
  • User-defined data objects and classes
  • Hardware abstraction layer
  • Development Environment
  • Board Support Package


This type of component of RTOS defines the schedule for all execution of entire tasks of process, but mostly all tasks are performed by priority system.

Synchronization Mechanism

With using this component of RTOS, it can be handled couples of task in parallel form, and improve the performance of entire system.

Memory Management

This component play vital role in the RTOS because this system helps for allocation the specific memory to every parts (Programs) of Real time operating system.

Function Library

Function Library works as a communication medium in between the Kernel and application code. With the help of application code, you can fire the all request to Kernel using function library, and finally they can yield the appropriate output.

Interrupt Service Mechanism

Interrupt Service Mechanism uses for handling a specific interrupt, which are stored in the RTOS layers.

I/O Management

This component of RTOS provides the better interface between the all INPUT/OUTPUT devices of computer system.

Fast Dispatch Latency

This component of Real Time OS maintains the interval gab between all completed tasks that are detected by the operating system.

User-Defined Data Objects and Classes

With the help of this component of Real Time OS, you can reduce the complexity of different programming languages such as C, C++, Java, and more, and it help to enhance the efficiency of entire system.

Hardware Abstraction Layer

Hardware abstraction layer gives the all access to computer operating system for making the interaction with hardware resources at the abstract level instead of entire detail them.

Development Environment

This component helps to develop environment between the user and hardware.

Board Support Package

This component of Real Time OS allows to users to identify the particular drivers and routines according their selection of H/W and S/W.

Function of Real time Operating System (RTOS)

The prime function of RTOS provides the better management of RAM and processor as well as it gives the access to all system resources.

Higher Priority Scheduler

Real Time OS contains different many priorities with range (32-256) for executing to every task. This scheduler helps to activate such process which has high priority. If current task is executing in CPU processors ZONE, then it go to further highest priority task, and run processes.

System Clock Interrupt Routine for Time Frame

System Clock Interrupt Routine helps to perform the highly time sensitive instructions in RTOS with using system clocks. In which, it allots the time frame for performing the specific tasks.

Deterministic Nature

Real Time OS provides the protection in using big length tasks such as 100 to 1000, and it determines the further highest priority task then executes them without getting delay.

Synchronization and Messaging

For making the communication medium in among of all tasks of one system to other system, RTOS use the synchronization and messaging. In which, synchronize the entire internally activities of event flag and can be sent text messages with using the mailbox, pipes and message queues.

Features of Real Time Operating System (RTOS)

Here, we will spread light on  numerous characteristics of RTOS such as 

  • It has better reliability. It means, RTOS can work in long time without any human interference.
  • Its result is more predictable because its every action are executed into predefined time frame.
  • Its performance is much better because it can perform more complex tasks without taking more workload.
  • All software and hardware are small size, which are used in the RTOS (Real Time Operating system).  Due to this, technician does not get more headaches for finding the errors in the RTOS.
  • Affordable Cost
  • It has good stability. So due to this feature, we can upgrade or downgrade to RTOS.
  • Consume low memory.
  • RTOS has better response time for highly predictability.
  • Occupy less resource.
  • Its environment is more unpredictable.
  • Kernel helps for storing the states of interrupted tasks for execution at appropriate time frame.

Advantages of Real Time Operating System

  • RTOS produces the more accurate result while getting maximum consumption of the all using resources, so it do not contain the down time.
  • RTOS contains very low time frame for shifting all task in own system.
  • In this type of RTOS, mainly focus on their currently running part instead of waiting stages. Due to this mechanism, they produce the exact output on the behalf of their execution task
  • RTOS is error free operating system.
  • RTOS can be used in the embedded system equipment because it is small size in nature.
  • RTOS is a more optimize operating system so this O/S can use in such product which are online all time like as refrigerator etc.
  • RTOS has more systematically memory allocation for every parts of the operating system.
  • RTOS is multitasking system.
  • RTOS allows the shorter ISR (Interrupt Service Routines).
  • Time allocation system is very excellent in RTOS.
  • Well designed inter task communication.
  • In RTOS, every task are executed according to “Priority Based Scheduling”, it means every tasks are performed in predefined time frame.
  • RTOS has more Maintainability & Extensibility.
  • RTOS works on the modularity principle, and due to that principle they help to reduce the memory wastage.
  • Due to modular nature, RTOS allows to modular task based testing.
  • RTOS coding is reusable.
  • RTOS is a scalable O/S.
  • Due to better Idle Processing system, RTOS is more reliable.
  • RTOS has bundle of drivers.
  • Well designed Power Management
  • RTOS allows the excellent protection.
  • RTOS has more speed up.
  • RTOS allows the MCU portability.

Disadvantages of Real time Operating System

  • Real Time OS can execute only limited task at same time frame.
  • It has not capable for performing the multi tasking and multi threading for long time , so it can execute only fewer tasks.
  • It has poor thread priority.
  • Hire most experienced designer for writing their algorithms because RTOS’s algorithms are very complicated.
  • Require specific device drivers and interrupts signals for giving request rapidly to interrupts.
  • It is more costly because RTOS needs many resources for performing tasks.
  • Need proficient programmer for writing the piece of code to RTOS.
  • RTOS uses the Low Priority Tasks.
  • In Real Time OS, use the error handling task very difficult.
  • It uses the non-trivial piece of processor cycles.
  • RTOS can switch only fewer tasks.

Examples of Real Time Operating System (RTOS)

Examples / Applications are:

  • Internet Technology
  • Medical Sector
  • Automobile Sector such as Anti-Lock Brake and Air Bag
  • Traffic Control System
  • Complex Multimedia System
  • For military as a Defense system such as RADAR
  • Use in Stock Exchange for updating all current information
  • Air traffic system
  • Airlines reservation system
  • Heart Pacemaker system
  • Robotics areas
  • Cameras
  • Telecom Communication
  • Scientific experiments for Nuclear reactors
  • Diagnosis image system
  • Industrial equipments
  • Fuel control injection system
  • Government system
  • Home appliance such as washing machine, microwave, and more


General Purpose Operating System

Real Time Operating System

  • GPOS uses the fair scheduling, it means GPOS’s scheduling no depends upon priority. 
  • Kernel is non preemptive nature
  • Priority inversion is unnoticed.
  • GPOS has not predictable.
  • GPOS optimization works as a average case.
  • GPOS contains huge memory.
  • GPOS examples are Linux, Windows, and IOS etc.
  • GPOS has Random Execution Pattern.
  • GPOS has unpredictable Response Times.
  • GPOS has not Time Bound.
  • GPOS is used in the PC, Laptop, and Tablet.
  • GPOS is designed to  multi user environment.
  • No scalable.
  • GPOS has high interrupt latency.
  • GPOS is less time sensitive.
  • GPOS has to secure memory modal.
  • RTOS uses the unfair scheduling such as its scheduling totally depends upon priority.
  • Kernel is preemptive nature.
  • Priority inversion is critical issue.
  • RTOS has predictable nature.
  • RTOS performs under worst case assumptions.
  • RTOS does not opt huge memory.
  • RTOS examples are Contiki source code, FreeRTOS etc.
  • RTOS has not random execution pattern.
  • RTOS has Predictable Response Times.
  • RTOS has Time Bound.
  • RTOS is used in the Embedded Computing system.
  • RTOS is designed to single user environment.
  • Scalable
  • RTOS has low interrupt latency.
  • RTOS is more time sensitive.
  • RTOS has to flat memory model.

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