• It is a special purpose operating system. It is used when rigid time requirement have been placed on the operation of a procedure or the flow of data.
  • It is often used as a control device dedicated to the application. System that controls scientific experiments, medical imaging system, industrial control system and certain display system are real time systems. Some automobile engines, fuel injection system, home appliance controllers and weapons systems are also real time systems.
  • A real time system has a well defined fixed time constraint in which processing must be done within that constraint otherwise the system will fail. A real time system functions correctly only if it returns the result within its time constraint. Contrast with time-sharing where it is desirable to respond quickly. A batch system, which may not have any time constraint at all. A real time system is divided into two systems:
  1. Hard Real Time System.
  2. Soft Real Time System

Hard Real Time System:

                                          It guarantees the critical task be completed on time. This whole requires that all delays in the system be bounded. This type of system cannot be mixed with any another operating system. Since none of any general-purpose operating system is configure in this type of operating system.

Soft Real Time System:

                                        This operating system is less restrictive than hard real time system. In this critical real time task gets a priority over other task. It can be mixed with other types of operating system. They are useful in multimedia, virtual reality and advance scientific method.