Hard Real Time System & soft Seal Time System

What is Real time Embedded System

Definition 1:

A real-time system is one that must process information and produce a response within a specified time, else risk severe consequences, including failure. That is, in a system with a real-time constraint it is no good to have the correct action or the correct answer after a certain deadline: it is either by the deadline or it is useless!

Definition 2 :

Any system in which the time at which output is produced is significant. This is usually because the input corresponds to some event in the physical world, and the output has to relate to that same event. The lag from input time to output time must be sufficiently small for acceptable timeliness

Definition 3 :

Any information processing activity or system which has to respond to externally generated input stimuli within a finite and specified period.

"A real-time system is one whose correctness is based on both the correctness of the outputs and their timeliness. The ‘novelty’ here is that the system is time critical."

Ex: A telephone switching system must feed dial tone to thousands of subscribers within a recommended limit of second.the software message Communication system involved have to work with in a limited time.