A real time operating system has well defined fixed time constraints. Process must be done within the defined constraints or the system will fail. \n\nAn example is the operating system for a flight control computer or an advanced jet airplane. \n\nOften used as a control device in a dedicated application such as controlling scientific experiments, medical imaging systems, industrial control systems, and some display systems. \n\nReal-Time systems may be either hard or soft real-time. \n\nHard real-time: \n\nA 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. Secondary storage limited or absent, data stored in short term memory, or read-only memory (ROM), Conflicts with time-sharing systems, not supported by general-purpose operating systems. \n\nSoft real-time: \n\nA 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 .Limited utility in industrial control of robotics, Useful in applications (multimedia, virtual reality) requiring advanced operating-system features.