5. spooling and buffering


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5. spooling and buffering

  1. 1. Basics of Operating Systems : Concept of Spooling and Buffering 1
  2. 2. RecapIn the last class, you have learnt about• Various Operating Systems• Single User Operating Systems• Multi-User Operating Systems 2
  3. 3. ObjectivesOn completion of this period, you would be able to know• Spooling• Buffering 3
  4. 4. Spooling• SPOOL : Simultaneous Peripheral Operation On-Line• A spool is a buffer that holds output for a device, such as a printer, that cannot accept interleaved data streams• Spooling overlaps input of one job with the computation of other jobs• The spooler may be reading the input of one job while printing the output of a different job as shown in next slide 4
  5. 5. Spooling Disk I/O Online CPUCard Reader Line Printer
  6. 6. Spooling Technique• A high speed device like a disk is interposed between a running program and a low speed device involved with the program input/output• Communication between a high speed device and low speed device is isolated• High speed device transfers the data to the spool• Low speed device gets the data from the spool 6
  7. 7. Advantages• Performance of the system is increased• CPU and I/O devices work more efficiently• Leads naturally to multiprogramming• Also used for processing data at remote sites 7
  8. 8. What is a Buffer ?A buffer is an area of main memory for holding data during input and output data transfers 8
  9. 9. Buffering• Overlaps the I/O of job with that of its own computation• After the data have been read and the CPU is about to start the operation, the input device is instructed to begin the next input operation• Both the CPU and I/O device are busy 9
  10. 10. Buffering
  11. 11. Buffering• By the time CPU is ready for next operation, the input device would have finished reading it• CPU creates data and puts into a buffer until an output device can accept it 11
  12. 12. Output Buffering• Processor stores the data in a buffer• Output device takes the data from the buffer 12
  13. 13. Input Buffering• Data transferred by an input channel is stored in the buffer• After the data transfer, the processor access the data from the buffer 13
  14. 14. Why Buffering ? Because of three reasons…• To cope with a speed mismatch between the producer and consumers of a data streams• To adopt between devices that have different data- transfer sizes• To support copy semantics for application I/O 14
  15. 15. Summary• Spool: Simultaneous Peripheral Operation On-Line• Spooling overlaps the I/O of one job with the computation of another job• A high speed device like a disk is interposed between a running program and a low speed device• Buffer is an area of main memory, which is used to store data temporarily during input and output data transfers• Spooling and buffering increases the system performance 15
  16. 16. Frequently Asked Questions1. Define the terms Spooling and Buffering2. Explain in detail Spooling and Buffering 16
  17. 17. Quiz1. Buffering overlaps the I/O of a job with its own computation • True • False2. SPOOL stands for simultaneous peripheral operation off line • True • False 17
  18. 18. Click here to see•Operating Systems•Basics of Operating Systems•Definition of Operating Systems•Other subject materials • Web designing • Micro processors • C++ tutorials • java home 18