Operating System-Unix [3i Infotech Placement]: Sample Questions 49 - 50 of 78

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Question 49

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Describe in Detail

Essay▾

What is the principle of locality?

Explanation

Define Principle of Locality
  • It is a term for the phenomenon in which the same values or related storage locations are frequently accessed.
  • It is also known as the locality of reference.
  • It happens because, the next most data items or instruction is the closed to the current data item or instruction.
  • Example: a block in a file may be the closed one that is needed next.
  • The OS can read the next block before its need and made it available it on hand at the time of issuing the actual read request.

Two types of principle of locality:

Two Types of Principle of Locality

Temporal locality

  • It refers to the reuse of speific data and resources.

Spatial locality

  • It refers to the use of data elements

Within relatively close storage locations.

  • Sequential locality is a special case of spatial locality which occurs when the data elements are arranged linearly in one-dimensional array.

Question 50

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Describe in Detail

Essay▾

What is validity fault?

Explanation

Interaction of Protection Fault and Validity Fault
  • Validity fault is the result of non-setting of valid bits in main memory at the time of referring a page by a process.
  • This happens when the pages are available outside the virtual address space of a process or the page are the part of the virtual address space but no physical address space is assigned to it.
  • The setting the valid bit of the page is the process making the page available for access in the memory.
  • The valid bit is not set for those pages:
    • That are outside the virtual address space of a process.
    • That are the part of the virtual address space of the process but no physical address is assigned to it.

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