What are the disadvantages of FCFS scheduling algorithm as compared to shortestjob first (SJF) scheduling?

First-Come, First-Serve (FCFS) and Shortest Job First (SJF) are two different types of scheduling algorithms used in operating systems to manage the execution of processes. Each has its own advantages and disadvantages. Here are some disadvantages of FCFS as compared to SJF:

1. Convoy Effect: In FCFS, if a process with a longer burst time arrives before a process with a shorter burst time, the shorter process has to wait for the longer process to finish. This is known as the convoy effect and it can lead to inefficiency and increased waiting times. On the other hand, SJF minimizes waiting time by executing the shortest jobs first.

2. Non-Preemptive: FCFS is non-preemptive, meaning once a process starts executing, it cannot be interrupted until it finishes. This can lead to poor performance if a shorter process arrives while a longer process is executing. SJF, on the other hand, can be either preemptive or non-preemptive.

3. Lack of Priority: FCFS does not consider the priority of processes. A high priority process may have to wait for a low priority process to complete if the low priority process arrived first. In contrast, SJF considers the length of the process, which can be seen as a form of priority.

4. Increased Waiting Time and Turnaround Time: FCFS can lead to increased waiting time and turnaround time, especially if a process with a long burst time arrives first. SJF minimizes waiting time and turnaround time by executing the shortest jobs first.

5. No Dynamic Behavior: FCFS does not adapt to changing circumstances. If a new process arrives that is shorter than the currently executing process, FCFS will not interrupt the current process to execute the new one. SJF, on the other hand, can adapt to changes and execute the new process if it is shorter.