The document discusses key concepts related to process management in operating systems, including processes, process states, process scheduling, and interprocess communication. It defines a process as a program in execution that includes a program counter, stack, and data section. Processes can be in one of several states like new, running, waiting, ready, and terminated. Process scheduling is managed using data structures like process control blocks and queues to track process states and allocate CPU resources. Common scheduling algorithms like FCFS, SJF, priority, and round robin are also covered.

1. Process Management
S.R INAMDARDept. of CSE BLDEA'S SSM POLYTECHNIC 1

2. UNIT 2: Processes
 Process Concept
 Process Scheduling
 Operations on Processes
 Cooperating Processes
 Inter process Communication
 Process Scheduling: Basic concepts
 Scheduling criteria
 Scheduling algorithms.
Dept. of CSE BLDEA'S SSM POLYTECHNIC 2

3. Process Concept
 A Program in execution is called as a process.
 A process is more than a program.
 A process includes
 program counter
 stack
 data section
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4. Process State Diagram
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5. Process State Diagram (cont..)
 As a process executes, it changes state
 new: The process is being created.
 running: Instructions are being executed.
 waiting: The process is waiting for some event to occur.
 ready: The process is waiting to be assigned to a process.
 terminated: The process has finished execution.
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6. Process Control Block (PCB)
Information associated with each process.
 Process state: ready ,new ,running etc.
 Program counter: address of next instruction to execute.
 CPU registers : PC, working registers, stack pointer.
 CPU scheduling information : scheduling order and priority.
 Memory-management information : page table/ segment table
pointers.
 Accounting information : amount CPU time used.
 I/O status information : list of I/O devices allocated to this
process and files (open).
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7. Process Control Block (PCB)
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8. Process Scheduling Queues
 Job queue – set of all processes in the system.
 Ready queue – set of all processes residing in main
memory, ready and waiting to execute.
 Device queues – set of processes waiting for an I/O
device.
 Process migration between the various queues.
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9. Schedulers
 Long-term scheduler (or job scheduler) – selects
which processes should be brought into the ready
queue.
 Short-term scheduler (or CPU scheduler) – selects
which process should be executed next and allocates
CPU.
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10. Schedulers (Cont.)
 Short-term scheduler is invoked very frequently (milliseconds) 
(must be fast).
 Long-term scheduler is invoked very infrequently (seconds, minutes)
 (may be slow).
 The long-term scheduler controls the degree of multiprogramming.
 Processes can be described as either:
 I/O-bound process – spends more time doing I/O than
computations, many short CPU bursts.
 CPU-bound process – spends more time doing computations; few
very long CPU bursts.
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11. Medium Term Scheduling
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12. Process Creation
 Parent process create children processes, which, in turn create
other processes, forming a tree of processes.
 Resource sharing
 Parent and children share all resources.
 Children share subset of parent’s resources.
 Parent and child share no resources.
 Execution
 Parent and children execute concurrently.
 Parent waits until children terminate.
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13. Process Creation (Cont.)
 Address space
 Child duplicate of parent.
 Child has a program loaded into it.
 UNIX examples
 fork system call creates new process
 exec system call used after a fork to replace the process’
memory space with a new program.
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14. Process Termination
 Process executes last statement and asks the operating system to decide
it (exit).
 Output data from child to parent (via wait).
 Process’ resources are de allocated by operating system.
 Parent may terminate execution of children processes (abort).
 Child has exceeded allocated resources.
 Task assigned to child is no longer required.
 Parent is exiting.
 Operating system does not allow child to continue if its parent
terminates.
 Cascading termination.
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15. Cooperating Processes
 Independent process cannot affect or be affected by the execution
of another process.
 Cooperating process can affect or be affected by the execution of
another process
 Advantages of process cooperation
 Information sharing
 Computation speed-up
 Modularity
 Convenience
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16. Interprocess Communication (IPC)
 Mechanism for processes to communicate and to
synchronize their actions.
 Message system – processes communicate with each
other without resorting to shared variables.
 IPC facility provides two operations:
 send(message) – message size fixed or variable
 receive(message)
 If P and Q wish to communicate, they need to:
 establish a communication link between them
 exchange messages via send/receive
 Implementation of communication link
 physical (e.g., shared memory, hardware bus)
 logical (e.g., logical properties)
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17. Interprocess Communication (IPC)
(contd..)
Communication may take place using either
message passing or shared memory.
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18. Process scheduling:Basic Concepts
 Maximum CPU utilization obtained with
multiprogramming
 CPU–I/O Burst Cycle – Process execution consists of a
cycle of CPU execution and I/O wait.
 CPU burst distribution
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19. Alternating Sequence of CPU
And I/O Bursts
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20. Scheduling Criteria
 CPU utilization – keep the CPU as busy as possible
 Throughput – # of processes that complete their
execution per time unit
 Turnaround time – amount of time to execute a
particular process
 Waiting time – amount of time a process has been
waiting in the ready queue
 Response time – amount of time it takes from when a
request was submitted until the first response is
produced, not output (for time-sharing environment)
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21. Dept. of CSE BLDEA'S SSM POLYTECHNIC 21

22. PROBLEM:
Consider the following set of process with the length of the
CPU & Burst time given in millisecond.
PROCESS BURST TIME PRIORITY
P1 10 3
P2 01 1
P3 02 3
P4 01 4
P5 05 2
With Gantt chart , calculate the Average Waiting Time &
Average Turn Around Time for FCFS , SJF, Priority & RR
Scheduling. The processes are assumed to arrive in the order
p1, p2, p3, p4,p5.
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23. FCFS(FIRST COME FIRST SERVE)
Gantt Chart:
P1
0 10
P2 P3 P4 P5
11 13 14 19
Waiting Time
P1  0
P2  10
P3  11
P4  13
P5  14
Average Waiting Time
AWT=Sum of all the Waiting Times/No. Process
AWT=p1+p2+P3+P4+P5/5
AWT=(0+10+11+13+14)/5
AWT=48/5
AWT=9.6 msDept. of CSE BLDEA'S SSM POLYTECHNIC 23

24. Turn Around Time
TAT=Waiting time + Burst Time
P1  0+10  10
P2  10+1  11
P3  11+2  13
P4  13+1  14
P5  14+5  19
Average Turn Around Time
ATAT=p1+p2+p3+p4+p5/5
ATAT=10+11+13+14+19/5
ATAT=67/5
ATAT=13.4ms
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25. SJF(SHORTEST JOB FIRST)
Gantt Chart:
P2
0 1
P4 P3 P5 P1
2 4 9 19
Waiting Time
P1  9
P2  0
P3  2
P4  1
P5  4
Average Waiting Time
AWT=Sum of all the Waiting Times/No. Process
AWT=p1+p2+P3+P4+P5/5
AWT=(9+0+2+1+4)/5
AWT=16/5
AWT=3.2 msDept. of CSE BLDEA'S SSM POLYTECHNIC 25

26. Turn Around Time
TAT=Waiting time + Burst Time
P1  9+10  19
P2  0+1  1
P3  2+2  4
P4  1+1  2
P5  4+5  9
Average Turn Around Time
ATAT=p1+p2+p3+p4+p5/5
ATAT=19+1+4+2+9/5
ATAT=35/5
ATAT=7 ms
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27. PRIORITY SCHEDULING
Gantt Chart:
P2
0 1
P5 P1 P3 P1
6 16 18 19
Waiting Time
P1  6
P2  0
P3  16
P4  18
P5  1
Average Waiting Time
AWT=Sum of all the Waiting Times/No. Process
AWT=p1+p2+P3+P4+P5/5
AWT=(6+0+16+18+1)/5
AWT=41/5
AWT=8.2 msDept. of CSE BLDEA'S SSM POLYTECHNIC 27

28. Turn Around Time
TAT=Waiting time + Burst Time
P1  6+10  16
P2  0+1  1
P3  16+2  18
P4  18+1  19
P5  1+5  6
Average Turn Around Time
ATAT=p1+p2+p3+p4+p5/5
ATAT=16+1+18+19+6/5
ATAT=70/5
ATAT=14 ms
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29. RR(ROUND ROBIN)
Gantt Chart:
P1
0
P2 P3 P4 P1P5P1P5 P1P1P5
2 3 65 108 12 1514 1917
Waiting Time
P1  (8-2)+(12-10)+(15-14)  9
P2  2
P3  3
P4  5
P5  6+(10-8)+(14-12)  10
P1  19-10 =9
P2  3-1=2
P3  5-2=3
P4  6-1=5
P5  15-5=10
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30. Average Waiting Time
AWT=Sum of all the Waiting Times/No. Process
AWT=p1+p2+P3+P4+P5/5
AWT=(9+2+3+5+10)/5
AWT=29/5
AWT=5.8 ms
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31. Turn Around Time
TAT=Waiting time + Burst Time
P1  9+10  19
P2  2+1  3
P3  3+2  5
P4  5+1  6
P5  10+5  15
Average Turn Around Time
ATAT=p1+p2+p3+p4+p5/5
ATAT=19+3+5+6+15/5
ATAT=48/5
ATAT=9.6 ms
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32. THANK
YOU
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