Operating System: Memory & Process Management

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Questions and Answers

What is the remaining burst time for Process P1 after Cycle 3?

5 (correct)

How many cycles does Process P2 take to completely finish execution?

1 (correct)

In which cycle does Process P3 reach a remaining burst time of 0?

Cycle 4

Cycle 3 (correct)

Cycle 2

Cycle 1

What strategy is used to schedule the processes in this example?

Round Robin Scheduling Signup and view all the answers

Which burst time value corresponds to Process P3 after Cycle 2?

1 Signup and view all the answers

Which element in the Gantt chart represents the process that starts first?

P₁ Signup and view all the answers

What is the significance of the 'Waiting Time' noted in the context?

It indicates the delay a process experiences before it begins execution. Signup and view all the answers

In the context of scheduling processes, what is the primary purpose of a Gantt chart?

To visualize the sequence of process execution. Signup and view all the answers

Which process in the given context is likely to have the highest waiting time initially?

P5 Signup and view all the answers

What action is indicated by 'Lukis Carta Gantt mengikut jadual baharu'?

Update the Gantt chart based on a new schedule. Signup and view all the answers

What is the initial waiting time for process B in a First In First Out (FIFO) scheduling?

0 ns Signup and view all the answers

What is the total waiting time for process A after considering its burst time?

3 ns Signup and view all the answers

How is the waiting time for process A calculated in a FIFO scheduling?

Waiting Time B + Burst Time A Signup and view all the answers

If the burst time of process B were to increase, how would that affect the waiting time of process A?

It would increase the waiting time for process A. Signup and view all the answers

What is the purpose of calculating the waiting time in process scheduling?

To minimize the overall completion time Signup and view all the answers

In FIFO scheduling, what is the effect of process A having a shorter burst time than process B?

It has no effect on the waiting time of process B. Signup and view all the answers

What would be the waiting time for process B if it were the only process running?

0 ns Signup and view all the answers

Which of the following statements about FIFO scheduling is true?

Processes are executed in the order they arrive in the queue. Signup and view all the answers

Which scheduling method is used to break the tie when two processes have the same next CPU burst?

First-Come, First-Served (FCFS) Signup and view all the answers

What characterizes the Preemptive Shortest Job First (SJF) approach?

Running processes are stopped to allow shorter processes to execute. Signup and view all the answers

In the Non-Preemptive Shortest Job First scheduling, which of the following statements is true?

The current process will complete before any new processes are considered. Signup and view all the answers

How is the waiting time (WT) determined in a Non-Preemptive SJF scheduling?

It is calculated based on the order they are completed. Signup and view all the answers

Which characteristic is NOT true for the Gantt Chart in Non-Preemptive SJF?

New processes can leapfrog current processes. Signup and view all the answers

What occurs if no arrival times (AT) are given in a Non-Preemptive SJF schedule?

All processes are assumed to arrive at the same time of zero. Signup and view all the answers

Which of the following best describes the main advantage of Shortest Job First scheduling?

It can lead to starvation of longer processes. Signup and view all the answers

What is the primary criterion for scheduling in the Shortest Job First method?

The length of the CPU burst time. Signup and view all the answers

What is the primary criterion for scheduling in the Shortest Job First (SJF) method?

Both the lowest arrival time (AT) and burst time (BT) are considered simultaneously. Signup and view all the answers

When P₃ is to be executed in the SJF scheduling, what condition is associated with its execution?

P₃ has the lowest burst time and arrives simultaneously with another process. Signup and view all the answers

In the event that multiple processes have the same arrival time, which aspect should be prioritized?

The process with the lowest burst time should be executed first. Signup and view all the answers

What happens if no other processes arrive by time zero besides P₃?

P₃ can begin execution immediately. Signup and view all the answers

What is indicated by the structure of a Gantt chart in the context of SJF scheduling?

It serves as a visual representation of the scheduling of processes over time. Signup and view all the answers

Which of the following is NOT a characteristic of the Shortest Job First scheduling algorithm?

It guarantees optimal wait time for all processes. Signup and view all the answers

What would be the implication of ignoring burst time (BT) in the SJF scheduling approach?

Processes may execute out of the most efficient order. Signup and view all the answers

In the scheduling scenario described, how is P₃'s position determined in comparison to other processes with the same arrival time?

P₃ takes priority based on its burst time over identical arrival times. Signup and view all the answers

Calculate the waiting time (WT) for process P₂ given the burst time (BT) for P₁ is 6 ms and the waiting time for P₁ is 5 ms.

11 ms Signup and view all the answers

In the Gantt chart, how does the arrival time (AT) of process P₃ relate to its burst and waiting times?

AT occurs after all previous processes have completed. Signup and view all the answers

What does BT represent in the context of process scheduling?

Burst Time Signup and view all the answers

Which formula accurately represents the calculation for waiting time in a sequential process queue?

WT(P₂) = WT(P₁) + BT(P₁) Signup and view all the answers

If the burst time for P₄ is 8 ms, and its waiting time is calculated after P₁, what will be the waiting time if the previous process had a waiting time of 11 ms?

19 ms Signup and view all the answers

What is the implication of having a negative waiting time in process management?

It indicates a processing error. Signup and view all the answers

How is the overall waiting time affected as more processes are added to the queue?

Overall waiting time increases. Signup and view all the answers

In a scheduling algorithm, which variable is commonly adjusted to optimize process management?

Burst Time (BT) Signup and view all the answers

Study Notes

Operating System Memory and Process Management

Topic 2: Memory and Process Management is part 3 of 4.
Learning Objectives (CLO1C2):
- Process management of operating systems.
- Gantt Chart drawing for FIFO, SJF, Priority, and Round Robin scheduling.
- Scheduling criteria calculation (waiting time, turnaround time, response time) for FIFO, Round Robin, SJF, and Priority.

Scheduling Algorithms

FIFO (First In First Out): Concept
- Processes are allocated CPU in the order they request it.
- Non-preemptive: Once a process starts, it finishes.
- Good for batch systems, not ideal for interactive ones.
- Turnaround time is unpredictable.
Shortest Job First (SJF): Concept
- CPU allocation prioritizes the process with the shortest next CPU burst.
- If bursts are equal, uses FCFS (First Come, First Served) to determine the order.
- Handles processes by their CPU cycle length.
- Two types:
  - Preemptive SJF (Shortest Remaining Time First - SRTF): Stops running a longer process when a shorter process becomes ready; prioritizes the process with the shortest remaining time to execute.
  - Non-preemptive SJF : Running processes finish before considering new ones.
Round Robin (RR): Concept
- Timesharing system design.
- Preemptive scheduling: Processes are assigned time slices (time quantum).
- Ready queue is a circular queue.
- CPU scheduler iterates through the ready queue, allocating each process up to one time quantum.
  - Efficient for interactive systems.
Priority Scheduling: Concept
- CPU allocation based on process priority -High Priority = Lower numbers -Low Priority = Higher numbers.
Non-preemptive: -Processes with higher priority run to completion before lower-priority ones do.
Main issue: Starvation (low-priority process may never get the CPU, hence the process gets starved)

Gantt Charts

Process Table includes process names, burst times, and waiting times.
Gantt Chart displays process names and timelines.
FIFO : First-in, First-out principle. Tasks arrive first, they finish first.
Other scheduling methods: The same principle is applied for different scheduling types, but the ordering in the chart reflects the respective algorithm and priorities.

Calculating Scheduling Criteria

The methods for calculating waiting time, turnaround time, response time for each scheduling type are outlined in the respective sections.

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Description

Explore the fundamentals of memory and process management in operating systems with this quiz. Assess your understanding of scheduling algorithms, including FIFO, SJF, and their calculations. Test your knowledge on Gantt Chart drawing and various scheduling criteria.