Operating Systems Scheduling Quiz

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Questions and Answers

What is considered the primary goal of maximizing CPU utilization in a scheduling algorithm?

To minimize response time

To increase waiting time

To reduce turnaround time

To keep the CPU as busy as possible (correct)

Which statement reflects the concept of turnaround time in process scheduling?

The time from submission to the first response

The time taken for a process to wait in the queue

The duration from when a process is created to its completion (correct)

The ratio of total execution time to number of processes

What is the primary disadvantage of the First-Come, First-Served (FCFS) scheduling algorithm?

It requires additional hardware resources.

It uses a complex scheduling criteria.

It leads to high average waiting time. (correct)

It cannot handle processes with varying burst times.

In the given example, what would be the total turnaround time for all processes combined?

30 milliseconds (A) Signup and view all the answers

In a First-Come, First-Served (FCFS) scheduling algorithm, how are processes executed?

In the order they arrive in the ready queue (A) Signup and view all the answers

What does waiting time represent in process scheduling?

The time spent waiting in the ready queue (B) Signup and view all the answers

If the processes P1, P2, and P3 have burst times of 24 ms, 3 ms, and 3 ms respectively, what is the average waiting time for these processes when using FCFS?

14 milliseconds (D) Signup and view all the answers

What is the response time for the first process (P1) in the FCFS scheduling scenario presented?

0 milliseconds (A) Signup and view all the answers

Which criterion aims to minimize the time from process request submission until the first response is produced?

Response time (D) Signup and view all the answers

Which of the following statements is true regarding the burst times of P1, P2, and P3 in the example?

The burst times are processed in the order of arrival. (B) Signup and view all the answers

In what state is a process when it is waiting for an event to occur?

Waiting (B) Signup and view all the answers

How does the FIFO queue structure impact the performance of the FCFS scheduling algorithm?

It does not prioritize shorter tasks over longer ones. (A) Signup and view all the answers

Which of the following best describes the throughput metric in a scheduling algorithm?

Total number of processes per time unit (C) Signup and view all the answers

Why might a scheduling algorithm prioritize minimizing waiting time?

To enhance responsiveness in a multi-user environment (D) Signup and view all the answers

What is the waiting time for process P2 in the initial scheduling scenario?

24 (C) Signup and view all the answers

How is the average waiting time calculated in the first scheduling scenario?

Sum of waiting times divided by the number of processes (D) Signup and view all the answers

In the second scheduling scenario where processes arrive in the order P2, P3, P1, what is the waiting time for process P3?

3 (D) Signup and view all the answers

What is the average waiting time for all processes in the second scenario?

3 (B) Signup and view all the answers

Under the First-Come, First-Served (FCFS) scheduling algorithm, what factor primarily affects waiting time for processes?

The order of arrival of processes (B) Signup and view all the answers

For process P1 in the first scenario, how much time does it wait before getting CPU time?

0 (B) Signup and view all the answers

What impact does a shorter burst time have on waiting time in an FCFS schedule?

Increases waiting time for subsequent processes (C) Signup and view all the answers

Which of the following statements about FCFS scheduling is true?

All processes are treated equally regardless of burst time. (B) Signup and view all the answers

Study Notes

First-Come, First-Served (FCFS) Scheduling

FCFS scheduling executes jobs in the order they arrive, following a first-in, first-out (FIFO) approach.
Simple implementation but generally suffers from high average waiting time, leading to poor performance.

Example of FCFS Scheduling - Case One

Processes:
- P1: 24 ms
- P2: 3 ms
- P3: 3 ms
Gantt Chart:
- P1 runs from 0 to 24
- P2 runs from 24 to 27
- P3 runs from 27 to 30
Waiting Times:
- P1: 0 ms
- P2: 24 ms
- P3: 27 ms
Average waiting time: (0 + 24 + 27) / 3 = 17 ms

Example of FCFS Scheduling - Case Two

Arrival Order:
- P2, P3, P1
New Gantt Chart:
- P2 runs from 0 to 3
- P3 runs from 3 to 6
- P1 runs from 6 to 30
Waiting Times:
- P1: 6 ms
- P2: 0 ms
- P3: 3 ms
Average waiting time: (6 + 0 + 3) / 3 = 3 ms
Improved performance compared to the first case.

Process Concept

A process represents a program in execution, acting as a unit of work in a system.
Processes require CPU time, memory, files, and I/O devices to complete tasks.
Example of a process: A task that displays file status by executing necessary instructions and system calls.

Process States

New: Process is being created.
Ready: Process is waiting for CPU assignment.
Running: Process instructions are currently being executed.
Waiting: Process is halted, waiting for an event.
Terminated: Process has completed execution.

Scheduling Algorithm Optimization Criteria

CPU Utilization: Maximize CPU activity for better efficiency.
Throughput: Maximize the number of processes completed per time unit.
Turnaround Time: Minimize the total time taken to execute a process.
Waiting Time: Minimize the duration a process remains in the ready queue.
Response Time: Minimize the time from request submission to the first response in time-sharing environments.

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Description

Test your understanding of process scheduling in operating systems with this quiz. It focuses on the concepts of burst time and Gantt charts, evaluating how well you can interpret and calculate timings. Perfect for students studying operating systems in computer science courses.