{"id":2227,"date":"2022-03-13T16:08:21","date_gmt":"2022-03-13T16:08:21","guid":{"rendered":"http:\/\/learnlearn.uk\/alevelcs\/?page_id=2227"},"modified":"2022-03-21T14:21:57","modified_gmt":"2022-03-21T14:21:57","slug":"process-management","status":"publish","type":"page","link":"https:\/\/learnlearn.uk\/alevelcs\/process-management\/","title":{"rendered":"Process Management"},"content":{"rendered":"
\n

Scheduling<\/h2>\n
\n\n

Process Scheduling<\/strong><\/p>\n

In computer systems multiple processes may be waiting to be executed by the processor and the processor needs to decided and how to schedule processing. There are multiple scheduling algorithms that can be used, depending on the system. These include:<\/p>\n

    \n
  • Round Robin<\/li>\n
  • First Come First Served<\/li>\n
  • Short Job First<\/li>\n
  • Shortest Remaining Time First<\/li>\n<\/ul>\n

    Process Priorities<\/strong><\/p>\n

    In most computer systems, processes have different priorities, depending on their function within the system.<\/p>\n\n<\/div>

    Calculations<\/h2>\n
    \n\n

    Process Scheduling Calculations<\/h3>\n

    Turnaround Time<\/strong><\/p>\n

    Turnaround time = Completion time – arrival time<\/span><\/p>\n

    This is the duration between a process arriving and it terminating<\/p>\n

    Waiting Time<\/strong><\/p>\n

    Waiting time = Turnaround time – burst time<\/span><\/p>\n

    This is how long a process waits idle before it is fully executed.<\/p>\n

    Average Waiting Time<\/strong><\/p>\n

    Average Waiting Time = Waiting time for all processes \/ Number of processes<\/span><\/p>\n

    This is how long a process has to wait on average before it is fully processed.<\/p>\n

     <\/p>\n\n<\/div>

    States<\/h2>\n
    \n\n

    Process States<\/h3>\n

    Processes can be in one of 3 states.<\/p>\n

    Running<\/strong><\/p>\n

    This is where the process is currently being executed by the processor<\/p>\n

    Ready<\/strong><\/p>\n

    This is where the process is loaded into memory, ready to be executed.<\/p>\n

    Blocked<\/strong><\/p>\n

    This is where the process is waiting for an event to occur before it is processed.<\/p>\n

     <\/p>\n\n<\/div>

    Round Robin<\/h2>\n
    \n\n

    Round Robin Scheduling<\/h3>\n

    In round-robin scheduling the processor works on each process in a circular manner. Each process is assigned an equal time-slice<\/strong> (aka quantum) for execution. Once the time-slice has been used up the\u00a0 process is blocked and will have to wait until the next time round to carry on executing. If a process completes before it reaches it’s quantum limit then it self terminates the processor moves onto the next process.<\/p>\n