The document discusses process schedulers. It defines scheduling as allowing one process to use the CPU while another process is on hold waiting for resources. The objectives of scheduling are to make the system efficient, fast, and fair. There are three types of schedulers: long term schedulers which select processes to load into memory, short term (CPU) schedulers which select the next process to run on the CPU, and medium term schedulers which swap processes in and out of memory during I/O waits. Common scheduling algorithms discussed include first come first serve, shortest job first, longest job first, round robin, and priority-based scheduling.

2. Presented by
Sub :- Operating Systems
Topic:-Process Schedulers
Respectected:-
Dr Huma javed UOP

3. • Scheduling definition
• Scheduling objectives
• Types of schedulers
• Different scheduling Algorithems
Content

4. Scheduling is a process which allows one process to
use the CPU while the execution of another process
is on hold due to unavailability of any resources.
It is a technique that is used when there are limited
resources and many process are competing for
them.
It’s aim is to make system efficient , fast and fair .
Scheduling

5. CPU
Utilization
• Computer usage of memory and processing
resources or amount of work handle by a CPU
Throughput
• It is the total number of process completed per unit
time.
Efficiency
• scheduler should keep the system busy whole time, if CPU and
all i/o devices can be kept running all the time more work can be done per
second.
Criteria for best scheduling algorithm

6. When a new process is created ,
a decision needs to be made
whether to run the
parent process or child process.
A scheduling decision must be
made when a process exits
When I/O interrupt occurs , a
scheduling decision may be
made.
Scheduling Objectives

7. Make the system fast
Increasing response
time
Increasing the output
Give better service to
processes
Maximize throughput
Main objective of scheduling !!!

8. If only one CPU is available , a choice has to
be made which process to run next.
The part of the operating system that makes
the choice is called the scheduler
Scheduler

9. Long term
scheduler
Short term
scheduler
Medium term
scheduler
Types of schedulers

10. It is also called job scheduler.
It determine which program are admitted to a
system for processing .
It selects process from queue and loads them
in to memory for execution .
When process changes the state from new to
ready, then there is use of long term scheduler.
Long term schedulers

11. It is also called CPU scheduler.
It is also called dispatchers.
Main objective is increasing system performance in accordance with
the chosen set of criteria .
CPU scheduler selects process among the processes that are ready to
execute and allocates CPU to one of them .
Faster than long term schedulers .
A dispatcher does the following:
 Switching context.
 Switching to user mode.
 Jumping to the proper location in the newly loaded program.
Short term schedulers

12. It is the part of swapping .
It removes the processes from memory .
A running process may become suspended if it
does not get I/O resource needed.
In this condition the process is move to the
secondary storage until it gets the resources.
It is the part of time sharing operating system.
Medium term schedulers

13. First Come
First Serve
(FCFS)
Shortest
Job First
(SJF)
Longest Job
First (LJF):
Round
Robin
Scheduling
Priority
Based
scheduling

14. From this topic we learn how the scheduler
works, and how scheduler allows one
process to use the CPU while the execution
of another process is on hold due to
unavailability of any resources .