Real-Time System

A real time process is a process that must respond to the events within a certain time period. A real time operating system is an operating system that can run real time processes successfully

Difference between Hard and Soft real-time systems: 

                        A hard real-time system guarantees that critical tasks complete on time. This goal requires that all delays in the system be bounded from the retrieval of the stored data to the time that it takes the operating system to finish any request made of it.

                        A soft real time system where a critical real-time task gets priority over other tasks and retains that priority until it completes. As in hard real time systems kernel delays need to be bounded

Important aspect of a real-time system or Mission Critical Systems:

                        A real time operating system has well defined fixed time constraints. Process must be done within the defined constraints or the system will fail. An example is the operating system for a flight control computer or an advanced jet airplane. Often used as a control device in a dedicated application such as controlling scientific experiments, medical imaging systems, industrial control systems, and some display systems. Real-Time systems may be either hard or soft real-time.

Hard real-time:

v  Secondary storage limited or absent, data stored in short term memory, or read-only memory (ROM)

v  Conflicts with time-sharing systems, not supported by general-purpose operating systems.

Soft real-time:

v  Limited utility in industrial control of robotics

Useful in applications (multimedia, virtual reality) requiring advanced operating-system features.