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12 process control blocks


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12 process control blocks

  1. 1. Understand Process Management : Process Control BlocksHOME PREVIOUS TOPIC NEXTPREVIOUS QUESTION PAPERS FOR OSCPP TUTORIALS 1
  2. 2. RecapIn the last class, you have learnt• Process, Process State Diagram• Sequential Process 2
  3. 3. Objectives On completion of this period, you would be able to know• Understand the Structure of Process Control Block 3
  4. 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 4
  5. 5. Process Control Block ( PCB ) 5
  6. 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 6
  7. 7. Process Control Block ( PCB )Pointer• It contains the address of another process which ispresent in the ready queueProcess State•It contains information about the state of the process i.e., •New •Ready •Running •Waiting •Halted 7
  8. 8. Process Control Block ( PCB )Program counter•The address of the next instruction to be executedCPU Registers•The registers vary in no. and type depending on thetype of computer architecture, they include: •Accumulators, index registers, stack pointers and general purpose registers 8
  9. 9. Process Control Block ( PCB )CPU scheduling information• This information includes – Process priority – Pointer to scheduling queues – Other scheduling parametersMemory management information• This information includes – Value of base and limit registers – Page tables – Segment tables 9
  10. 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 10
  11. 11. CPU Switch from Process to Process Process 0 Process 1executing Save state into PCB0 idle Reload state from PCB1 idle Interrupt or system call executing Save state into PCB1 idle Reload state from PCB0executing 11
  12. 12. SummaryIn 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 12
  13. 13. Quiz1. PCB stands for process control board a) True b) False2.Process control block does not contain any information about process state . a) True b) False3.The information stored in a PCB varies from process to process. a) True b) False 13
  14. 14. Frequently Asked Questions1. Explain the structure of a process control block with the help of a diagram. 14
  15. 15. Other subject materials• Web designing• Micro processors• C++ tutorials• javahome