CPU Scheduling Algorithms: FCFS, SJF, and Round Robin Quiz Quiz

Enhance your understanding of CPU scheduling algorithms with this quiz focused on First-Come First-Served (FCFS), Shortest Job First (SJF), and Round Robin methods. Answer questions covering key principles, differences, advantages, and scenarios for these central process scheduling techniques.

1. Identifying FCFS Algorithm

   Which CPU scheduling algorithm schedules processes strictly in the order they arrive in the ready queue?

   1. Shortest Job First (SJF)
   2. Preemptive Priority
   3. Round Robin
   4. First-Come First-Served (FCFS)

   Explanation: First-Come First-Served (FCFS) schedules processes in the exact order they arrive without any prioritization. Shortest Job First (SJF) schedules based on the shortest burst time, not arrival order. Round Robin cycles through processes with a time slice, and Preemptive Priority uses priority levels, not arrival time. Therefore, only FCFS matches the described behavior.

2. Main Feature of SJF

   What main characteristic distinguishes the Shortest Job First (SJF) scheduling algorithm from FCFS?

   1. SJF schedules processes based on memory size
   2. SJF runs the longest process first
   3. SJF selects the process with the shortest next CPU burst time
   4. SJF only handles I/O-bound processes

   Explanation: SJF uniquely selects the process with the shortest upcoming CPU burst for execution, reducing average waiting time. Running the longest process first would describe Longest Job First, not SJF. Memory size and process type are unrelated to how SJF orders processes. The correct distinction is based on shortest burst time.

3. Round Robin Time Quantum

   In Round Robin scheduling, what is the main role of the time quantum (also called time slice)?

   1. It limits how long a process runs before the next process is scheduled
   2. It determines the arrival order of processes
   3. It sets the maximum number of processes in the system
   4. It controls the memory usage limit per process

   Explanation: The time quantum in Round Robin controls the maximum time a process can run before being swapped out for the next process. Arrival order is not affected by the quantum; that's part of the ready queue. Number of processes or memory usage are unrelated to the function of the time quantum.

4. Non-Preemptive Nature

   Which of these is always a non-preemptive scheduling algorithm?

   1. Preemptive Priority
   2. Preemptive SJF
   3. Round Robin
   4. First-Come First-Served (FCFS)

   Explanation: FCFS is inherently non-preemptive, meaning a running process cannot be interrupted until it finishes. Preemptive SJF and Preemptive Priority can interrupt processes, while Round Robin is also preemptive due to its time slicing. Only FCFS fits the described non-preemptive behavior.

5. Response Time Measurement

   If process P arrives at time 0 and starts executing at time 4, what is its response time?

   1. 0
   2. 1
   3. 4
   4. 4 + 0 = 4

   Explanation: Response time is calculated as the time from arrival to the first scheduled execution, which is 4 in this case. Option 0 is incorrect as the process starts at 4, not immediately. Option 1 is not relevant to this scenario, and 4 + 0 = 4, although numerically correct, is redundant and not the standard phrasing.

6. SJF and Starvation

   Why can the Shortest Job First (SJF) algorithm cause starvation for certain processes?

   1. It always uses the largest time quantum
   2. It ignores process priorities
   3. Long processes may never get scheduled if shorter ones keep arriving
   4. It processes tasks based strictly on arrival time

   Explanation: SJF can indefinitely delay longer processes if there is a continual flow of short jobs, leading to starvation. Time quantum is not used in SJF as it's not a time-sliced algorithm. Arrival time and priorities are not exclusive factors in pure SJF, making the other options incorrect or less appropriate.

7. Average Waiting Time in FCFS

   When compared to SJF, the FCFS algorithm generally results in which type of average waiting time?

   1. Zero waiting time for all jobs
   2. Lower average waiting time
   3. Exactly the same waiting time
   4. Higher average waiting time

   Explanation: FCFS tends to have a higher average waiting time because all processes, regardless of their burst time, wait for previous jobs to finish, especially if a long job is at the front. SJF typically reduces average waiting time by scheduling shorter jobs first. The other options do not accurately reflect the differences between the algorithms.

8. Context Switching in Round Robin

   What happens frequently in Round Robin scheduling as a direct result of time quantum expiration?

   1. Context switching between processes
   2. Memory thrashing
   3. I/O starvation
   4. Deadlock among processes

   Explanation: Each time the time quantum expires, the running process is preempted and the CPU switches context to the next process, which is known as context switching. Deadlock and memory thrashing are generally unrelated to Round Robin’s quantum mechanism, and I/O starvation is not a direct result of time quantum expiration.

9. Shortest Remaining Time First

   Which of the following is a preemptive version of the SJF algorithm?

   1. Largest Job Next
   2. Shortest Remaining Time First (SRTF)
   3. Earliest Deadline First
   4. Non-Preemptive FCFS

   Explanation: Shortest Remaining Time First (SRTF) is the preemptive variant of SJF, allowing a new process with a shorter predicted burst to preempt the running process. Largest Job Next is not related to SJF. Non-Preemptive FCFS and Earliest Deadline First are different scheduling strategies.

10. Best Algorithm for Time-Sharing

    In time-sharing operating systems, which CPU scheduling algorithm is preferred for fairness among users?

    1. SJF
    2. Round Robin
    3. FCFS
    4. FIFO (First In First Out)

    Explanation: Round Robin is most suitable for time-sharing as it allocates equal time slices to all processes, ensuring fairness. SJF may lead to starvation, and FCFS and FIFO can unfairly favor earlier arrivals. FIFO is essentially another name for FCFS and does not address interactive fairness.