SJF (Shortest Job First) in Operating Systems - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does SJF stand for in operating systems?

SJF stands for Shortest Job First, a scheduling algorithm that selects the process with the smallest execution time to run next.

beginner

How does SJF scheduling decide which process to run?

SJF chooses the process that requires the least amount of CPU time among the available processes.

intermediate

What is the main advantage of SJF scheduling?

It minimizes the average waiting time for processes, making the system more efficient in handling tasks quickly.

intermediate

What is a major drawback of SJF scheduling?

It can cause starvation, where longer processes may wait indefinitely if shorter jobs keep arriving.

advanced

Is SJF scheduling preemptive or non-preemptive?

SJF can be both: non-preemptive SJF runs a process to completion once started; preemptive SJF (also called Shortest Remaining Time First) can interrupt a running process if a shorter job arrives.

What does SJF scheduling prioritize?

A Process with the highest priority number

B Process that arrived first

C Process with the shortest execution time

D Process with the longest execution time

SJF always selects the process with the shortest execution time to run next.

Which problem can SJF scheduling cause?

A Starvation of longer processes

B Deadlock

C High CPU utilization

D Fairness to all processes

SJF can cause starvation because longer processes may wait indefinitely if shorter jobs keep arriving.

What is the main goal of SJF scheduling?

A Minimize average waiting time

B Maximize throughput

C Ensure fairness

D Maximize CPU idle time

SJF aims to minimize the average waiting time for all processes.

In preemptive SJF, what happens if a new shorter job arrives while another is running?

A The running job continues until completion

B The running job is interrupted and the shorter job runs

C Both jobs run simultaneously

D The new job waits until the running job finishes

Preemptive SJF interrupts the current process if a shorter job arrives.

Which of these is NOT true about SJF scheduling?

A It can be preemptive or non-preemptive

B It can cause starvation

C It always reduces average waiting time

D It is easy to know exact job lengths in practice

In real systems, exact job lengths are often unknown, making SJF hard to implement perfectly.

Explain how the Shortest Job First scheduling algorithm works and its main benefits.

Think about how choosing the smallest task first affects waiting times.

Describe the potential problem of starvation in SJF scheduling and why it happens.

Consider what happens if short tasks keep coming before longer ones get CPU time.