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5. spooling and buffering
- 1. Basics of OperatingSystems : Concept of Spooling and Buffering 1
- 2. Recap In the lastclass, you have learnt about • Various Operating Systems • Single User Operating Systems • Multi-User Operating Systems 2
- 3. Objectives On completion ofthis period, you would be able to know • Spooling • Buffering 3
- 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. Spooling Disk I/O Online CPU Card Reader Line Printer
- 6. Spooling Technique • Ahigh 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. Advantages • Performance ofthe 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. What is aBuffer ? A buffer is an area of main memory for holding data during input and output data transfers 8
- 9. Buffering • Overlaps theI/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
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- 11. Buffering • By thetime 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. Output Buffering • Processorstores the data in a buffer • Output device takes the data from the buffer 12
- 13. Input Buffering • Datatransferred by an input channel is stored in the buffer • After the data transfer, the processor access the data from the buffer 13
- 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. Summary • Spool: SimultaneousPeripheral 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. Frequently Asked Questions 1.Define the terms Spooling and Buffering 2. Explain in detail Spooling and Buffering 16
- 17. Quiz 1. Buffering overlapsthe I/O of a job with its own computation • True • False 2. SPOOL stands for simultaneous peripheral operation off line • True • False 17
- 18. Click here tosee •Operating Systems •Basics of Operating Systems •Definition of Operating Systems •Other subject materials • Web designing • Micro processors • C++ tutorials • java home 18