The key difference between hard and soft real time system is that, a hard-real time system is a system in which a single failure to meet the deadline may lead to a complete system failure while a soft real time system is a system in which one or more failures to meet the deadline is not considered as complete system failure, but its performance is considered degraded.
An operating system is a system software that manages the computer hardware according to the instructions provided by the software. An operating system provides various tasks. File management, memory management, controlling peripheral devices and process scheduling are some of them. One type of an operating system is a real time operating system. It can be divided into hard real time systems and soft real time systems.
CONTENTS
1. Overview and Key Difference
2. What is Hard Real Time System
3. What is Soft Real Time System
4. Side by Side Comparison – Hard vs Soft Real Time System in Tabular Form
5. Summary
What is Hard Real Time System?
A real time system is a data processing system. The time taken by the system to respond to an input and provide the output or display the updated information is known as the response time. So, in these systems, the response time should be very minimum. The system should complete the task within the deadline. In a real-time operating system, the correctness of the system output depends on the logical result of computation as well as the time it takes to produce the result. Their systems also have a structure similar to an ordinary operating system. It also has mechanisms for real time scheduling tasks.
Figure 01: Air Traffic Control System
In hard real time system, the time requirement is a critical constraint. The system should perform within the deadline. If the system didn’t perform within the deadline, it is considered as a task failure. These types of systems should not miss the deadline. Missing the deadline can be catastrophic. Air traffic control systems, missile, and nuclear reactor control systems are few examples for hard real time systems. If the aircraft control system didn’t give the instructions to the aircraft within the deadline, it can cause the air craft to crash. Therefore, in a hard-real time system, meeting the deadline is extremely important. These systems are deployed mainly into safety critical systems.
What is Soft Real Time System?
In a soft real time, system, the time requirement is not very crucial. The system should perform the task or give the output within the deadline but there can be a small tolerance occasionally. If the system, did not perform the task within the deadline it is not considered as a failure as long as it provides the required output. But performance is considered to be degraded. Missing the deadline will not cause a catastrophic event like in a hard-real time system. These systems are less restrictive. Some examples of software real-time systems are multimedia streaming, advanced scientific projects, and virtual reality.
What is the Difference Between Hard and Soft Real Time System?
Hard vs Soft Real Time System |
|
| A hard-real time system is a system in which a failure to meet even a single deadline may lead to complete or catastrophic system failure. | A soft real time system is a system in which one or more failures to meet the deadline is not considered as complete system failure but that performance is considered to be degraded. |
| Restrictive Nature | |
| A Hard-real time system is very restrictive. | A Soft real time system is not very restrictive. |
| Deadline | |
| A Hard-real time system should not miss the deadline. Missing the deadline cause complete or catastrophic system failure. | A Soft real time system can miss the deadline occasionally. Missing the deadline is not considered as a complete system failure but degrades the performance. |
| Utility | |
| A hard-real time system has more utility. | A soft real time system has less utility. |
| Examples | |
| Air traffic control systems, missile, and nuclear reactor control systems are some examples of hard real time systems. | Multimedia streaming, advanced scientific projects, and virtual reality are some examples of soft real time systems. |
Summary – Hard vs Soft Real Time System
This article discussed two types of real time operating systems; the hard real time systems and the soft real time systems. The difference between hard and soft real time system is that, a hard-real time system is a system in which a single failure to meet the deadline may lead to a complete system failure while a soft real time system is a system in which one or more failures to meet the deadline is not considered as complete system failure but its performance is considered degraded.
Reference:
1.PantechProLabs India Pvt Ltd. “RTOS Basic Concepts.” LinkedIn SlideShare, 10 Dec. 2012. Available here
2.“Types of Operating System.”, Tutorials Point, 8 Jan. 2018. Available here
Image Courtesy:
1.’Flickr – Official U.S. Navy Imagery – A Sailor operates the SPN-43 air search radar system while standing approach control.’By Official Navy Page from United States of AmericaMass Communication Specialist Petty Officer 2nd Class (AW/SW) Gretchen M. Albrecht/U.S. Navy – A Sailor operates the SPN-43 air search radar system while standing approach control., (Public Domain) via Commons Wikimedia