Introduction:
The First Come First Serve (FCFS) algorithm is a scheduling algorithm used in operating systems to determine the order in which processes are executed. This algorithm assigns the CPU to the processes in the order they arrive in the ready queue. While FCFS may be suitable for certain scenarios, it can be particularly troublesome for time-sharing systems.

Explanation:
Time-sharing systems are designed to provide efficient and fair CPU allocation to multiple users or processes. They aim to maximize CPU utilization, minimize response time, and ensure fairness among users. However, the FCFS algorithm does not consider the execution time or priority of processes, leading to several issues in time-sharing systems.

1. Convoy Effect:
The FCFS algorithm can cause a phenomenon called the "convoy effect" in time-sharing systems. When a long-running process arrives before short-running processes, it occupies the CPU for an extended period. This results in other processes waiting in the ready queue, causing a convoy-like effect where short processes get delayed due to the presence of a long-running process.

2. Poor Response Time:
In time-sharing systems, users expect a quick response from the system. However, the FCFS algorithm may lead to poor response times for interactive processes. If a CPU-intensive process arrives before interactive processes, the interactive processes have to wait until the CPU-intensive task completes.

3. Lack of Prioritization:
FCFS does not consider the priority of processes. In time-sharing systems, it is crucial to prioritize certain processes based on their importance, deadlines, or user requirements. FCFS treats all processes equally, which can lead to a lack of prioritization and inefficient resource allocation.

4. No Preemption:
FCFS does not support preemption, which is essential in time-sharing systems. Preemption allows higher-priority processes to interrupt and suspend lower-priority processes to ensure fairness and responsiveness. Without preemption, long-running processes can monopolize the CPU, leading to delays and poor performance for other processes.

Conclusion:
In summary, the FCFS algorithm is particularly troublesome for time-sharing systems due to the convoy effect, poor response times for interactive processes, lack of prioritization, and the absence of preemption. To address these issues, other scheduling algorithms like Round Robin, Priority Scheduling, or Multilevel Queue Scheduling are commonly used in time-sharing systems to improve fairness, response times, and overall system performance.