Operating System [3i Infotech Placement]: Sample Questions 66 - 68 of 81

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Question 66

Operating System
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Write in Short

Short Answer▾

What is the window of the working set of a process?

Explanation

  • Some models uses a parameter k as the working-set window.
  • The idea is to examine the most recent k page references.
  • The set of pages in the most recent k page references is the working set.
  • If a page is in active use, it will in the working set.
  • If page is no longer used, it will drop from the working set k units after its last reference.

Question 67

Operating System
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Describe in Detail

Essay▾

Is the process before and after the swap are the same?

Explanation

Swapping of Two Processes
  • Process before swapping is residing in the primary memory in original form.
  • All regions however are not occupied by the process with few empty slots in the regions. While swapping kernel ignores empty slots.
  • After swapping the process resides in the swap device.
  • The regions swapped out will not have empty slots that were present before assigning.
  • When the process is brought again into the main memory kernel referring takes care of the empty slots in the regions.

Question 68

Operating System
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Describe in Detail

Essay▾

How do you create special files like named pipes and device files?

Explanation

  • Special files are created by the system call ‘mknod’ .
  • Special file is created using following steps:
    • New inode is assigned by kernel.
    • Sets the file type as a pipe, directory or special file.
    • If the file type is a device file, major and minor device numbers are the two entries created.
  • Using the mknod command, special files are created:
    • mknod [options] name type [major minor] .
  • Example:
    • For a disk, disk controller is the major device number and the disk is the minor device.
  • Unix example:
    • $ mknod < pipe name > p

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