1. Understand Process Management
: Process Control Blocks
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2. Recap
In the last class, you have learnt
• Process, Process State Diagram
• Sequential Process
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3. Objectives
On completion of this period, you would be able to
know
• Understand the Structure of Process Control Block
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4. Process Control Block
• Each process is represented in the operating
system by a Process control block ( PCB )
• PCB is also called a Task Control Block
• PCB contains specific information associated to
a process
• PCB consisting of various information is shown
in next slide
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6. Process Control Block ( PCB )
Process control block consists of following information:
• Pointer
• Process state
• Process number
• Program counter
• CPU Register
• CPU-Scheduling Information
• Memory-Management Information
• Accounting Information
• I/O status Information
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7. Process Control Block ( PCB )
Pointer
• It contains the address of another process which is
present in the ready queue
Process State
•It contains information about the state of the process i.e.,
•New
•Ready
•Running
•Waiting
•Halted 7
8. Process Control Block ( PCB )
Program counter
•The address of the next instruction to be executed
CPU Registers
•The registers vary in no. and type depending on the
type of computer architecture, they include:
•Accumulators, index registers, stack pointers and general
purpose registers
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9. Process Control Block ( PCB )
CPU scheduling information
• This information includes
– Process priority
– Pointer to scheduling queues
– Other scheduling parameters
Memory management information
• This information includes
– Value of base and limit registers
– Page tables
– Segment tables 9
10. Process Control Block ( PCB )
Accounting information:
•This information includes
•Amount of CPU and real time used
•Time limits
•Account numbers
•Job or Process no.s etc.
I/O status information
•This information includes
•List of I/O devices allocated to the process
•List of open files, etc
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11. CPU Switch from Process to Process
Process 0 Process 1
executing
Save state into PCB0
idle
Reload state from PCB1
idle Interrupt or system call executing
Save state into PCB1
idle
Reload state from PCB0
executing
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12. Summary
In this class, you have learnt
• The structure of a Process Control Block
• Various pieces of information associated with a specific
process
• The sequence of activities that occur when CPU
switches from process to process
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13. Quiz
1. PCB stands for process control board
a) True
b) False
2.Process control block does not contain any
information about process state .
a) True
b) False
3.The information stored in a PCB varies from
process to process.
a) True
b) False
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