1. The Teacher Computing Scheduling [CP5]

2. The Teacher Computing Multiprogramming A number of jobs are queued and loaded into memory to be processed. A number of different jobs may be stored in memory at the same time. Each job in memory is allocated a small amount of processing time in turn(a time slice).

3. The Teacher Computing Scheduler The Scheduler is the part of the operating system that decides the order in which jobs are allocated time slices of processing time.

4. The Teacher Computing Jobs Each job in memory can be… –Running (being processed) –Ready (waiting to be processed) –Blocked (in the middle of being processed but temporarily stopped)

5. The Teacher Computing Jobs loaded into Memory… All jobs are READY The scheduler selects one for processing…..at the end of the time- slice the scheduler selects another job for processing…..and so on. Each job gets a time-slice of processing time.

6. The Teacher Computing Blocking During a program’s time slice of processing, it may need some I/O… The I/O is started and the program is ‘Blocked’ so it cannot be processed until I/O is finished… Other programs continue to be processed… …until I/O is finished. The status is set back to ‘Ready’…

7. The Teacher Computing Priorities The scheduler may allocate priorities to jobs waiting to be processed. Those with higher priorities are more likely to be selected for processing.

8. The Teacher Computing Scheduling Policies Priority allocation may take into account: –The size of the job. (Small jobs may getter higher priority because they can be processed quickly) –Whether the job requires I/O –The time the job has been waiting for processing. (To prevent jobs getting stuck in the queue)