In this post we are going to learn about the What is Real-Time System and Types of Real-Time System which is very easily explained below. This is very interesting topic. There is trending in Quora also.
What is Real-Time System: Definition of RTS
A computer system which is the response on the time is known as Real-Time System. A system that satisfies bounded response time constraint or risk of system failure.
In real-time computing, the correctness depends on the time at which the results are produced not only depends upon the logical result. A Deadline is the given time after a event when a response time has completed.
Key Terms of Real-Time System
- The ability of the operating system to provide the necessary level of service in a bound response time
- It responds to inputs immediately(Real-Time)
- Here the task is completed within a specified time delay
- Real-time computing is equivalent to fast computing
- Necessary signaling between interrupt routines and task code is handled by RTS
- Real-time systems operate in a static environment
- Real-time programming includes assembly coding, priority intercept programming, writing device drivers
Example of Real-time system
- In real life situations like controlling a traffic signal or a nuclear reactor or an Aircraft.
- Mobile Phones, Digital Camera, Microwave Oven
- Avionics, Radar Control System, Industrial Process Control
- Command and Control
- Multimedia system
- Electronics Warhead Control System
- Missile Tracking System
Logical / Temporal Correctness
- If a system misses its time limit then the resulting action can be canceled, can continue, depending on the system option.
- Its specification includes logical / temporal correctness
Logical correctness: Indicates that the system should produce the correct output (must be verifiable)
Temporal correctness: Implies that system must produce output at the correct or right time
CPU Architectures & Structure of a Real-Time System
- The Component of RTOS is its kernel - Monolithic & Microkernel.
Characteristics of the Real-Time System
- Failure cost is high
- Concurrency and Multiprogramming Require
- Requirements of Reliability and fault-tolerant
- Predictable behavior
- Computation - Offline (precomputed) and Online (Dynamically)
- Priority - Static and Dynamic
- Scheduling - Preemptive and Non-Preemptive
Now we are going to describe the type of Real-Time System.
Type of Real-Time System
Real-Time system can be characterized as
- Hard Real-Time Systems
- Soft Real-Time Systems
- Firm Real-Time System
1. Soft Real-Time System:
- This System should meet timings constraints. Response time overrun leads to disastrous damage.
- Here utility value becomes less/drops with time
- Exam hall: Delay by 30 minutes allowed. If you very delay then you will not be allowed to appear in the exam.
- Word processors
- Airline reservation system
2. Hard Real-Time System:
- Deadline overruns are tolerable, but not desired.
- There is no frightening consequence of missing one or more time limits.
- If a task does not meet the deadline then the system crashes.
- A difficult time limit is put on a job because late results produced by the job after the deadline can have disastrous consequences.
Example: Onboard computer of a moving aircraft
- Measures velocity, height, position, acceleration, air pressure, etc.
- Scheduled time collects data with a sensor within 20 minutes
- Compares these data against the stored values
3. Firm Real-Time System:
- The system does not fail but throws the results (ignores) in case of failure.
- The system does not fail but throws the results (ignores) pass the deadline.
- Every 1/30 second has to come in the frame.
- Frames will not wait for the destination to arrive but switch to the next frame if the 6th frame does not arrive
- Hard RTS are not periodic
- Most periodic hard real-time system companies are RT systems
Example: Video Conferencing
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