Shortest Job First MCQ Quiz in मल्याळम - Objective Question with Answer for Shortest Job First - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

Key Points

   Shortest Job First (SJF) is an algorithm in which the process having the smallest execution time is chosen for the next execution. This scheduling method can be preemptive or non-preemptive. It significantly reduces the average waiting time for other processes awaiting execution. The full form of SJF is Shortest Job First.
The processes should execute in an SJF manner to get the lowest waiting time. If a process starts the execution the remaining process has to wait until it completes in a non-preemptive scheduling algorithm. So, the order should be 5, 9, 12, 18. 

Hence the correct answer is 5, 9, 12, 18.

Scheduling Algorithm: Shortest Remaining Time First (Pre-emptive)

Gantt chart:

0       3        5        8       12      15      21

Formula:

Turnaround time = Completion time – Arrival time.

Process Table:

Average turnaround time = \(\frac{{\left( {8\; + \;2\; + \;7\; + \;14\; + \;5} \right)}}{5} = 7.2\;msec\)

Average waiting time = \(\frac{{\left( {2\; + \;0\; + \;3\; + \;8\; + \;2} \right)}}{5} = 3\;msec\)

Difference = 7.2 - 3 = 4.2

Important Points:

TAT = CT - AT

WT = TAT - ET

Concept:

Transferring the control of CPU from one process to another demands saving the context of currently running process and loading the context of another ready process. This mechanism of saving and restoring the context is known as context switching.

Explanation:

Round robin scheduling:

It is pre-emptive scheduling algorithm which considers all the processes as equally important and treats them in favourable manner. Each process in ready queue gets a fixed amount of CPU time known as time quantum. If the process does not execute completely till end of time quantum, it is pre-empted and CPU is allocated to the next process in the ready queue. Context switching is needed in round robin scheduling.

Preemptive SJF:

It is also known as shortest remaining time first scheduling. Scheduler always chooses the process for execution that has the shortest remaining processing time. While a process is being executed, CPU can be taken back from it and can be assigned to some newly arrived process is burst of new process is shorter than its remaining burst time.

Non – preemptive SJF:

It is also known as shortest process next. In this, at any point of time among all the ready processes, the one having the shortest CPU burst time is scheduled first. There is no context switching in this algorithm.

Preemptive priority:

Concept:

Shortest remaining time next:  pre-emptive scheduling

In shortest remaining time next, when a process of less burst time(run time) arrives than in ready queue then context switch will happen

Explanation:

Time           Running                  Remaining times at the end

0 – 3             A                                 A – 9  B – 7

3 – 6             B                                 A – 9  B – 4  C – 2

6 – 8             C                                 A – 9  B – 4  D – 5

8 – 9             B                                 A – 9  B – 3  D – 5  E – 2

9 – 11            E                                 A – 9  B – 3  D – 5

11 – 12          B                                 A – 9  B – 2  D – 5  F – 12

12 – 14          B                                 A – 9  D – 5  F – 12

14 – 19          D                                 A – 9  F – 12

19 – 28          A                                 F – 12

The correct answer is 2

Explanation:

Assume that: P4 < P3

Gantt chart:

0           1            2            3           4          4+Z        7+Z

Process Table1:

Average waiting time = 1

\(\frac{{1 + 0 + \left( {1 + z} \right) + 0}}{4} = 1\)

The value of Z is 2.

Assume that: P4 ≥p3

Gantt chart:

0           1            2            3           4            7          7+Z

Process Table2:

Given average waiting time = 1

\(But\;\frac{{1 + 0 + 1 + 3}}{4} \ne 1\)

\(\frac{5}{{4}} \ne 1\)

\(∴ p4 > p3\;is\;not\;possible\;\)

∴ Z = 2

Shortest job first scheduling algorithm uses min heap data structure for its implementation. 

If there are n tasks and each task has to be inserted to the heap and later extracted from the heap, it results in a running time of O(nlogn).

Therefore, Shortest job first scheduling algorithm uses min heap data structure and has O(nlogn) time complexity.​

Shortest job first scheduling algorithm uses min heap data structure for its implementation. 

If there are n tasks and each task has to be inserted to the heap and later extracted from the heap, it results in a running time of O(nlogn).

Therefore, Shortest job first scheduling algorithm uses min heap data structure and has O(nlogn) time complexity.​

The correct answer is Processor Management.

Key Points

• Processor Management is the function of an operating system that allocates CPU time to various processes.
  • This ensures that all active processes receive a fair share of the CPU's processing power.
  • The operating system uses scheduling algorithms to determine the order in which processes are given CPU time.
  • Common scheduling algorithms include First-Come, First-Served (FCFS), Shortest Job Next (SJN), and Round Robin (RR).
  • Processor management also involves managing process states and transitions, such as from running to waiting, or from waiting to ready.
  • Proper processor management ensures efficient CPU usage, responsiveness, and system stability.

Additional Information

• Processor management is a critical component of multitasking operating systems, allowing multiple processes to run concurrently.
• It helps in prioritizing processes, so that important tasks receive more CPU time compared to less critical ones.
• Advanced processor management techniques include multi-core processing and parallel processing, which further enhance system performance.
• Historically, early operating systems had simpler processor management techniques, but modern systems use complex algorithms to improve efficiency.

Concepts:

Shortest remaining time first (SRTF), is a scheduling method that is a pre-emptive version of shortest job first (SJF).

In this scheduling algorithm, the process with the smallest amount of time remaining until completion is selected to execute.

Explanation:

At t = 0:

Only Process P₁ is available and hence P₁ is executed for 1 ms.

At t = 1:

Process P₁ and Process P₂ are available, between them P₂ has least burst time. Therefore, P₁ gets pre-empted and hence P₂ is executed for 1 ms.

At t = 2:

All three process are available. Since P₂ is having least burst time it executes till its completion followed by Process P₁ and process P₃ respectively

Gantt chart:

Preemptive SJF scheduling is equal to SRTF

Concept:

Transferring the control of CPU from one process to another demands saving the context of currently running process and loading the context of another ready process. This mechanism of saving and restoring the context is known as context switching.

Explanation:

Round robin scheduling:

It is pre-emptive scheduling algorithm which considers all the processes as equally important and treats them in favourable manner. Each process in ready queue gets a fixed amount of CPU time known as time quantum. If the process does not execute completely till end of time quantum, it is pre-empted and CPU is allocated to the next process in the ready queue. Context switching is needed in round robin scheduling.

Preemptive SJF:

It is also known as shortest remaining time first scheduling. Scheduler always chooses the process for execution that has the shortest remaining processing time. While a process is being executed, CPU can be taken back from it and can be assigned to some newly arrived process is burst of new process is shorter than its remaining burst time.

Non – preemptive SJF:

It is also known as shortest process next. In this, at any point of time among all the ready processes, the one having the shortest CPU burst time is scheduled first. There is no context switching in this algorithm.

Preemptive priority: