Real-time systems are a class of embedded systems where the time of reaction is critical. The consequences of not reacting in time vary between different applications. Based on severity, real-time systems are classified as follows:
- Hard real time: Missing a deadline is not acceptable and considered a system failure. These are usually mission-critical systems in airplanes, cars, and power plants.
- Firm real time: Missing a deadline is acceptable in rare cases. The usefulness of the result is zero after the deadline. Think about a live streaming service. A video frame delivered too late can only be discarded. This is tolerable provided it happens infrequently.
- Soft real time: Missing a deadline is acceptable. The usefulness of results degrades after the deadline, causing degradation of the overall quality, and should be avoided. Such an example is...