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Questions and Answers
What is the main purpose of scheduling in a system?
What is the main purpose of scheduling in a system?
Which type of scheduling allows the OS to assign resources to a process for a predetermined period?
Which type of scheduling allows the OS to assign resources to a process for a predetermined period?
What is the function of the Job Queue in a system?
What is the function of the Job Queue in a system?
What type of scheduler determines which processes are to be admitted into the system?
What type of scheduler determines which processes are to be admitted into the system?
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Which type of scheduling is used when a process terminates?
Which type of scheduling is used when a process terminates?
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What is the function of the Short-term Scheduler (CPU Scheduler)?
What is the function of the Short-term Scheduler (CPU Scheduler)?
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What is the primary advantage of the First-Come, First-Served scheduling algorithm?
What is the primary advantage of the First-Come, First-Served scheduling algorithm?
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What is the function of the Medium-term Scheduler?
What is the function of the Medium-term Scheduler?
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What type of scheduling is used when a process switches from running state to ready state?
What type of scheduling is used when a process switches from running state to ready state?
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What is the formula to calculate the Turnaround Time of a process?
What is the formula to calculate the Turnaround Time of a process?
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Which of the following is NOT a characteristic of the Shortest Job Next (SJN) scheduling algorithm?
Which of the following is NOT a characteristic of the Shortest Job Next (SJN) scheduling algorithm?
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What is the Response Time of a process?
What is the Response Time of a process?
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What is the term for the moment when a process enters the ready queue and awaits execution by the CPU?
What is the term for the moment when a process enters the ready queue and awaits execution by the CPU?
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What is the formula to calculate the Waiting Time of a process?
What is the formula to calculate the Waiting Time of a process?
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In the FCFS scheduling algorithm, which process will be executed first?
In the FCFS scheduling algorithm, which process will be executed first?
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What is the waiting time for P3?
What is the waiting time for P3?
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What is the primary purpose of context switching in operating systems?
What is the primary purpose of context switching in operating systems?
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Which of the following statements is true about FCFS?
Which of the following statements is true about FCFS?
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When does context switching happen?
When does context switching happen?
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What is the definition of a thread in operating systems?
What is the definition of a thread in operating systems?
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What is the burst time for P5?
What is the burst time for P5?
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What is an advantage of using threads in operating systems?
What is an advantage of using threads in operating systems?
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What is the average waiting time for the given processes?
What is the average waiting time for the given processes?
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What type of thread is managed by the operating system kernel?
What type of thread is managed by the operating system kernel?
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In FCFS, which process will be executed last?
In FCFS, which process will be executed last?
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What is the state of a thread when it is waiting for resources?
What is the state of a thread when it is waiting for resources?
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What is the arrival time for P4?
What is the arrival time for P4?
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What is the purpose of calculating the average waiting time?
What is the purpose of calculating the average waiting time?
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What is process scheduling in operating systems?
What is process scheduling in operating systems?
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Why is creating and managing threads less costly than processes?
Why is creating and managing threads less costly than processes?
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What is the main characteristic of Non-preemptive SJF scheduling?
What is the main characteristic of Non-preemptive SJF scheduling?
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What is the main advantage of Priority Scheduling?
What is the main advantage of Priority Scheduling?
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What is the solution to Starvation in Priority Scheduling?
What is the solution to Starvation in Priority Scheduling?
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What is the main characteristic of Preemptive SJF scheduling?
What is the main characteristic of Preemptive SJF scheduling?
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What is the main disadvantage of Priority Scheduling?
What is the main disadvantage of Priority Scheduling?
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What is the main characteristic of Round Robin scheduling?
What is the main characteristic of Round Robin scheduling?
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What is the main difference between Preemptive SJF and Non-preemptive SJF?
What is the main difference between Preemptive SJF and Non-preemptive SJF?
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What is the term for a process running out of resources because other processes are using it?
What is the term for a process running out of resources because other processes are using it?
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Study Notes
Context Switching
- Involves switching the CPU from one process to another, ensuring smooth execution of multiple processes.
- Happens when a high-priority process comes to a ready state, an interrupt occurs, user and kernel-mode switch, or preemptive CPU scheduling is used.
Threads in Operating Systems
- Definition: The smallest unit of a process that can be scheduled and executed by the CPU.
- Importance: Allows parallelism within a process, leading to more efficient and faster execution.
- Types of Threads:
- User-Level Threads (ULTs): Managed by user-level libraries, with fast context switch and no OS modification required.
- Kernel-Level Threads (KLTs): Managed by the operating system kernel, with the OS managing and scheduling threads independently.
Advantages of Using Threads
- Responsiveness: Allows a program to continue running even if part of it is blocked.
- Resource Sharing: Threads of the same process share memory and resources.
- Economy: Creating and managing threads is less costly than processes.
- Scalability: Threads can run on different processors in a multiprocessor system.
Thread Lifecycle
- New: Thread is created.
- Runnable: Thread is ready to run.
- Running: CPU is executing the thread.
- Blocked: Thread is waiting for resources.
- Terminated: Thread has finished execution.
Process Scheduling in Operating Systems
- Definition: The method by which the operating system decides which process runs at any given time.
- Importance: Ensures efficient execution of processes, optimal CPU utilization, and overall system performance.
Categories of Scheduling
- Non-preemptive: A process's resource cannot be taken before the process has finished running.
- Preemptive: The OS assigns resources to a process for a predetermined period, and the process switches from running state to ready state or from waiting state to ready state during resource allocation.
Types of Schedulers
- Long-term Scheduler (Job Scheduler): Determines which processes are to be admitted into the system and brings the new process to the 'Ready State'.
- Short-term Scheduler (CPU Scheduler): Selects which process should be executed next and brings process from the ready state for scheduling it on the running state.
- Medium-term Scheduler: Manages swapping of processes in and out of memory to balance load.
Scheduling Queues
- Job Queue: All processes in the system.
- Ready Queue: Processes that are ready to run.
- Device Queue: Processes waiting for devices (I/O).
Scheduling Algorithms Overview
- Two types of scheduling methods:
- Preemptive Scheduling: Used when a process switches from running state to ready state or from waiting state to ready state.
- Non-Preemptive Scheduling: Used when a process terminates, or when a process switches from running state to waiting state.
CPU Scheduling Algorithms
- First-Come, First-Served (FCFS): Processes are executed in the order they arrive.
- Shortest Job Next (SJN): Processes are executed in the order of their burst time.
- Priority Scheduling: Processes are assigned priority numbers, and the highest priority process is selected next.
- Round Robin (RR): Each process is allocated a fixed time slot (time quantum), and if a process does not finish execution within its time quantum, it is preempted and placed at the end of the ready queue.
Key Concepts in CPU Scheduling
- Arrival Time: The moment in time when a process enters the ready queue and is awaiting execution by the CPU.
- Burst Time: The amount of CPU time the process requires to complete its execution.
- Completion Time: The summation of the arrival, waiting, and burst times.
- Turnaround Time: The time elapsed between the arrival of a process and its completion.
- Waiting Time: A process's duration in the ready queue before it begins executing.
- Response Time: The duration between the arrival of a process and the first time it runs.
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Description
This quiz covers the concept of context switching, which involves switching the CPU from one process to another, ensuring smooth execution of multiple processes.
