Hello.... Dear views Scheduling is most important Role in OS..... in this ppt i described very Creatively about Process Scheduling...... I hope you like it..... and easily understand it...... :-) :-)

2. CONTENT…

3. INTRODUTION
OF
PROCESS
SCHEDULERS

4. PROCEES
SCHEDULER
A series of action or steps taken in order to
achieve a particular end.
A program that arranges computer’s operation
into an appropriate sequence.
A machine that organizes or maintain schedulers.
A process is a program during execution

5. PROCESS SCHEDULER
INTRODUCTION:
Multiprogramming is to have some process running at all times, to Maximum CPU
Utilization. To meet these objectives, the Process Scheduler selects available process
for a program execution of the CPU.
For a single-processor system, there will never be more than one running process, if
there are more processes, the rest will have to wait until the CPU is free and can be
Rescheduled.
A process migrates among the various scheduling queues throughout its lifetime. The
operating system must select, for scheduling purpose, processes from these queues in
some fashion. The selection process is carried out by the appropriate Scheduler.
Often, in Batch System, more processes are submitted than can be executed
immediately. These processes are spooled to a mass-storage device(Disk), where
they are kept for later execution.
The Long-term scheduler, or Job scheduler, selects processes from this pool and
loads them into memory for execution.
Whenever the CPU becomes IDLE the operating system must select one of the
processes in the Ready Queue to be executed.
The Short-term scheduler, or CPU scheduler, selects from among the processes that
are ready to execute and allocates the CPU to one of them.

6. STATE OF PROCESS
Start/New
Ready
Execution/Running
Waiting
Swapped
 Terminate

7. start Terminated
Diagram of process state
Start to Ready= Long Term Scheduler
Ready to Running= Mid Term Scheduler
Running to Waiting or waiting to ready= Short Term Scheduler

8. Process Control Block(PCB):-

9. TYPES OF PROCESS SCHEDULERS……
S.NO TYPES
1 Process Scheduler/CPU Scheduler
1.) Preemptive
2.) Non-Preemptive
2 Long- Term Scheduler
3 Medium- Term Scheduler
4 Short-Term Scheduler
5 Dispatcher

10. Process Scheduler /CPU Scheduler
Process scheduler is a part of the operating system that decides which process
runs at a certain point in time.
When CPU becomes idle the OS must select one of the processes in Ready Queue to be
executed
CPU Scheduler selects a process from the processes in memory that are ready to execute
(from Ready queue),allocates the CPU to one of them
CPU scheduling decisions may take place when a process:
 Switches from running to waiting state
 Terminates
 Switches from running to ready state. (e.g. when time slice of a process expires or an
interrupt occurs)
 Switches from waiting to ready state. (e.g. on completion of I/O)
 On arrival of a new process
The OS code that implements the CPU scheduling algorithm is known as CPU scheduler

11. In Pre-emptive scheduling the currently running process may be
interrupted and moved to the ready state by OS (forcefully)
In Non-preemptive Scheduling, the running process can only lose the
processor voluntarily by terminating or by requesting an I/O. OR, Once
CPU given to a process it cannot be preempted until the process
completes its CPU burst
Pre-emptive scheduling & Non-preemptive scheduling

12. Long Term Scheduler
 Determines which programs are admitted to the
system for processing
 Controls the degree of multiprogramming
 More processes, smaller percentage of time each
process is executed

13. Medium Term Scheduler
Part of the swapping function
Based on the need to manage the degree
of multiprogramming

14. Short Term Scheduling
Known as the dispatcher
Executes most frequently
Invoked when an event occurs
Clock interrupts
I/O interrupts
Operating system calls

15. Scheduling Criteria
Maximum Utilization of CPU
Waiting time should be minimum
Turn around time should be minimum
Response time should be minimum
Arrival time should be minimum
Note:- Total time taken by the process is called Turn around time.