Basic CS-Operating System [TCS Placement]: Sample Questions 16 - 17 of 35

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Question 16

Operating System
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Describe in Detail

Essay▾

What is a binary semaphore? What is its use?

Explanation

  • A binary semaphore takes only as values.
  • They are used to implement mutual exclusion and synchronize concurrent processes.
  • It can be used for guarding critical section and also for guarding single resource.
  • To show the usage of binary semaphore, we are going to implement a print queue that can be used by concurrent tasks to print their jobs.
  • This print queue will be protected by a binary semaphore, so only one thread can print at a time.
  • Semaphore value 1 indicates, resource is available, 0 means it is not available.
Given the Image is Defining the Binary Semaphore

Question 17

Operating System
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Describe in Detail

Essay▾

Define the process life cycle

Explanation

  • When a process executes, it passes through different states.
  • These stages may differ in different operating system, and the names of these states are also not standardized.
  • Process can have one of the following five states at a time.
  • States:
    1. New
    2. Running
    3. Ready
    4. Waiting
    5. Terminated
Given the Image Define the Process Can Have One of the Following Five States at a Time
Table of State and Its Description
StateDescription
StartThis is the initial state when a process is first started or created.
Ready
  • The process is waiting to be assigned to a processor.
  • Ready processes are waiting to have the processor allocated to them by the operating system so that they can run.
  • Process may come into this state after Start state or while running it by but interrupted by the scheduler to assign CPU to some other process.
RunningOnce the process has been assigned to a processor by the OS scheduler, the process state is set to running and the processor executes its instructions.
WaitingProcess moves into the waiting state if it needs to wait for a resource, such as waiting for user input, or waiting for a file to become available.
TerminatedOnce the process finishes its execution, or it is terminated by the operating system, it is moved to the terminated state where it waits to be removed from main memory.

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