Hard Real-Time Computing/Scheduling in Operating System


Hard Real-Time Computing/Scheduling in Operating System

Real time computing is divided in two parts or two types. Hard real-time systems and soft real-time systems. Here, Hard real-time systems are required to complete a critical task with in a specified amount of time. A process is submitted along with a statement of the needed timein which the process should be completed of perform I/O. The scheduler then either admits the process, guranteeing that the process will complete in the given time. If the schedular thinks that the process cannot be completed in given time than it rejects the request.  This is known as resource reservation.

resource reservation. To give such a gurantee it requires the scheduler to know exact what time does it requires to complete a given process/request.  However, such a intelligence is impossible with secondary storage or virtual memory because these subsystems cause unavoidable and unforeseeable variation in the mount of time to execute a particular process. Therefore, hard real-time systems are composed of special purpose software sunning on hardware which are dedicated to their critical process, and lack the functionality of modern computers and operating systems.