Real Time Operating System in OS


Real-Time Operating System (RTOS) is an operating system which guarantees output or response within a specified time constraint. In other words, a real-time operating system works in real time utilizing deterministic constraints and optimizing time usage by avoiding unexpected delays.

Real time Operating System

Constituents of RTOS

RTOS comprises multiple components which are as follows:

1. Scheduler: It decides the order of execution for tasks and threads based on a priority scheme.

2. Symmetric Multiprocessing: RTOS efficiently handles multiple tasks processing to ensure the parallel processing of code.

3. Function Library: A standard interface that can hold the Application Program Interface (API) to call functions within it. It connects the respective application code to the kernel. Primarily, Application code directs requests to the kernel through function libraries.

4. Context Switching Time: It is the time that a scheduler takes to switch tasks between one running thread and another. 

5. Memory Management: Memory management is done by the operating system to ensure adequate memory is available to run a program and to refer to an object stored in memory.

Type of RTOS 

The real-time operating system can be classified in three categories:

Hard Real Time Operating System

Hard real-time systems are a deterministic system that must operate within a stringent time frame. In other terms, these systems are considered to have failed if they are unable to perform the function within the deadline. For example, the Aircraft control system, anti-lock brake, etc. Precisely, hard real-time systems are critical systems which can prove deadly if they do not operate in specified time.

Soft Real time Operating System

Soft real-time operating systems are also time-bound operating systems. However, these systems do not have a critical timeline, which can be missed and operations can be delayed by some time. For example, the reservation system, digital camera, mobile phones, etc.

Firm Real-Time Operating System

The firm real-time operating system operates within time constraints, for example, Visual inspection in industrial automation, video conferencing, etc. The time limits in these systems are not stringent, but if these deadlines are missed, it is highly likely that some undesired results may occur.

Learn more about types of operating system here.

Applications of RTOS

RTOS finds application in the following domains:

Industrial Applications

• Chemical Plant Control

• Automated Car Assembly Plant

• Supervisory Control And Data Acquisition (SCADA)

Medical Applications

• Robot Used in Recovery of Displaced Radioactive Material

Peripheral Equipment

• Laser Printer

Automotive and Transportation

• Multi-Point Fuel Injection (MPFI) System

Telecommunication Applications

• A Cellular System


• Computer On-board an Aircraft

Internet and Multimedia Applications

• Video Conferencing

• Cell Phones

Defense Applications

• Missile Guidance System


• Railway Reservation System