Answer to Question #212445 in Computer Networks for Baudouin

Question

Using one of the referenced website articles discuss how operating systems Switch Between Processes and/or how the OS decides to stop one process and start another.

Answer 1

The operating system the operating system maintains several queues for processes before allocating processor time. The ready queue contains processes that are ready to be allocated processor time and can run in case they are allocated the processor. The decision on which process should run next from the queue depends on the scheduling algorithm in use such as FCFS, Round Robin, SJF e.tc For instance For FCFS(First Come First Served) the processes will be allocated on the order in which they came into the queue. The first to get in the ready queue will be the first to get allocation of the processor and memory by the scheduler.

An operating can switch a processes based on various factors:

a) Expiration of time slide for the current process-If the allocated time that a process should run expires and the process has not yet completed execution, it is moved to the ready queue and has to wait the next allocation and an new process is allocated the processor to run.

b) When a higher priority process is brought in the queue- This is common in priority scheduling algorithms.

c) When the current process is waiting for an input output(I/O). The operating system switches this process and new process is waiting to complete the I/O while in the waiting queue.

d) Completion of the current running process-If the current running process has completed execution, the operating system has to bring in the next awaiting process from the ready queue.