Difference between the First-Come-First-Served (FCFS) and Shortest Job First (SJF) in operating systems

 

Here is a comparison between the First-Come-First-Served (FCFS) and Shortest Job First (SJF) scheduling algorithms in CPU Scheduling in operating systems :

Feature	First-Come-First-Served (FCFS)	Shortest Job First (SJF)
Definition	A scheduling algorithm where processes are executed in the order they arrive in the ready queue	A scheduling algorithm where the process with the shortest burst time is executed first
Task prioritization	Based on arrival time	Based on burst time
CPU utilization	Average CPU utilization may not be optimal	Average CPU utilization is optimal
Latency	High Latency	Low Latency

Responsiveness	High waiting time for processes, leading to low responsiveness	Lower waiting time for processes, leading to high responsiveness
Memory requirements	Does not require any additional memory for scheduling information	Requires additional memory for scheduling information
Task completion	May result in longer completion time for tasks	Results in shorter completion time for tasks
Performance prediction	Difficult to predict performance	Easy to predict performance
Overhead	Lower overhead compared to SJF	Higher overhead compared to FCFS
Load balancing	May result in unequal distribution of load	Results in balanced distribution of load
Real-time applications	Not suitable for real-time applications	Suitable for real-time applications
Batch processing	Suitable for batch processing	Suitable for batch processing
Multitasking	Suitable for multitasking	Suitable for multitasking
Scheduling decisions	Based on arrival time	Based on burst time
Process state	Process state information is not required	Process state information is required
Predictability	Poor predictability	Good predictability
Starvation	Can lead to starvation of long processes	Prevents starvation of long processes
CPU utilization	Lower average CPU utilization	Higher average CPU utilization

In conclusion, both FCFS and SJF are scheduling algorithms used in CPU Scheduling in operating systems. FCFS executes processes in the order they arrive in the ready queue, while SJF executes the process with the shortest burst time first. FCFS has lower overhead, is simple to implement and is suitable for batch processing and multitasking, but may result in high latency, low responsiveness and poor predictability. On the other hand, SJF has higher overhead, requires additional memory and results in higher average CPU utilization, but provides low latency, high responsiveness and good predictability. The choice of scheduling algorithm depends on the specific requirements and constraints of the system and the workload being scheduled.