Basic CS-Operating System [3i Infotech Placement]: Sample Questions 15 - 17 of 89

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Question 15

Operating System
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Describe in Detail

Essay▾

What is cycle stealing?

Explanation

The Cycle Stealing
  • A method of accessing computer memory or bus without interfering with the CPU.
  • Similar to direct memory access for allowing I/O controllers to read or write RAM without CPU intervention.

Cycle Stealing and DMA

  • The DMA controller uses the data bus when the CPU does not need it.
  • Forces the CPU to temporarily suspend operation.
  • Cycle stealing is done only at specific break points in an instruction cycle when DMA takes control of the bus system and communicates directly with the memory.
  • Cycle-stealing allows DMA controller to transfer data to and from RAM.
  • Allows IO devices to use the RAM without separate memory.

Question 16

Operating System
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Write in Short

Short Answer▾

When does the condition ‘rendezvous’ arise?

Explanation

  • In OS rendezvous condition is related to message passing.
  • Rendezvous is a condition when receiver and sender are blocked until message is delivered
  • Sender is blocked upon sending and receiver is blocked waiting for message.
  • Thus, both sender and receiver are blocked and message is passed from sender to receiver.

Question 17

Operating System
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Describe in Detail

Essay▾

What are short, long and medium-term scheduling?

Explanation

Long-Term Scheduler vs Short-Term Scheduler

Long Term Scheduler

  • Also called job scheduler.
  • Determines programs admitted to system for processing.
  • Selects processes from the queue and loads into memory for execution.
  • Processes load into the memory for CPU scheduling.

Short Term Scheduler

  • Also called CPU scheduler.
  • Increase system performance based on chosen criteria.
  • Changes ready state to running state of the process.
  • Faster than long-term schedulers.

Medium Term Scheduler

  • A part of swapping.
  • Removes the processes from the memory.
  • Reduces the degree of multiprogramming.
  • Running process may become suspended if it makes an I/O request.

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