3i Infotech Placement: Sample Questions 443 - 444 of 1245

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Question 443

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Describe in Detail

Essay▾

How do you change file access permissions?

Explanation

  • chmod command changes file permissions with the.
  • In Unix, file permissions establish the different types of access to a file by both access and classe types.
  • The access classes are “user” , “group” , “other” and “all” - User who owns the file, a specific group of users, the other remaining users who are not in the group.
  • Read, write and execute are the access types- determine what may be done with file by each access class.

There are two ways of using chmod to change file permissions:

  • Symbolic method:
    • This is the first and probably easiest way.
    • Is relative method- specifies access class and types with single letter abbreviations.
  • Absolute form:
    • Specifies a set of three numbers that determine all the access classes and types.

Question 444

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Describe in Detail

Essay▾

What is an OS? What are components of OS?

Explanation

Understanding of Operating System
  • OS program acts as an interface between the user and the computer hardware controlling the execution of all kinds of programs.
  • Used to run other programs and applications.
  • Performs basic tasks-
    • Recognizing input from the keyboard
    • Sending output to the display screen
    • Keeping track of files and directories on the storage drives
    • Controlling peripheral devices, such as printers.

Components of Operating Systems

  • Kernel:
    • Provides basic control to all of the computer՚s hardware devices.
    • Manages memory for programs in the RAM.
  • Program execution:
    • Provides an interface between an application program and the computer hardware.
    • Allows application program to interact with the hardware.
  • Interrupts:
    • Automatically saves local register contexts, and running specific code in response to events.
    • Computers support hardware interrupts, and allow the programmer to specify code run when that event takes place.
  • Memory management
  • Multitasking, disk access and file system management.
  • Networking & security
  • Graphical user interface:
    • The modern computer systems support graphical user interfaces.
    • Evolve over time.

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