3i Infotech Placement: Sample Questions 333 - 335 of 1245

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Question 333

Describe in Detail Essay▾

What are the bits that support the demand paging?

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Explanation

Understanding of Demand Paging
  • Note the following parts of the page table entry, which includes physical address of the page and protection bits.
    • Page address
    • Age
    • Copy on write
    • Modify
    • Reference
    • Valid
  • A modified bit is set if the page has been altered since it was last loaded into main memory- an unset bit means page does not have be written to the disk when swapped out.
  • Other control bits represent protection and permission at the page level.
    • A read-only/read-write bit.
    • Kernel page or user page.

Question 334

Write in Short Short Answer▾

What is the base class for all swing components?

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Explanation

  • Swing components are derived from abstract javax. swing. Jcomponet class.
  • Which has following hierarchy:

java. lang. Object

java. awt. component

java. awt. container

javax. swing. jcomponent

It replaces selection of AWT GUI components.

Question 335

Describe in Detail Essay▾

Describe the storage allocation and scope of global, extern, static, local and register variables?

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Explanation

  • Storage allocation concerns with the memory that is, where the storage space is allocated for variables and functions.
  • Scope of a variable is implicitly determined by its storage allocation.
  • Storage allocation is specified by the keywords auto, extern, static and register.
  • ‘auto’ variables
    • Store in the memory storage.
    • Majority of the variables in a program.
    • Their scope might be local or global.
  • ‘extern’ variables
    • Global variables and can be declared in another source file which could be external
    • They are obviously allocated on the heap accessible across function calls etc.
  • ‘register’ variables
    • Allocated in the CPU registers.
    • Storage and accessibility is faster than other variables as they are stored in CPU itself.
    • Use for variables with repeated usage or critical access time.
  • ‘static’ variables
    • Survive lifetime of the program and unlike global variables provide limited scope.
    • These variables are automatically initialized to zero and could be specified as ‘auto’ and ‘extern’ variables.
    • The values are retained, even though they are declared in local scope, between the repeated function calls to the same function.