CPU Scheduler Implementation

This is a C program that implements various CPU scheduling algorithms commonly studied in Operating Systems. The program provides a menu-driven interface to demonstrate the working of different scheduling algorithms with visualization through Gantt charts.

Features

• Implementation of 4 CPU scheduling algorithms:

  1. First Come First Serve (FCFS)
  2. Shortest Job First (Non-Preemptive)
  3. Shortest Job First (Preemptive) / Shortest Remaining Time First (SRTF)
  4. Round Robin (with configurable time quantum)

• For each algorithm, the program displays:

  • Gantt Chart visualization
  • Process completion details in tabular format
  • Average Waiting Time
  • Average Turnaround Time

Compilation and Usage

To compile the program:

gcc scheduler.c -o scheduler

To run the program:

./scheduler

Input Format

1. First, enter the number of processes
2. For each process, enter:
   • Arrival Time (AT)
   • Burst Time (BT)
3. Choose the scheduling algorithm from the menu
4. For Round Robin, additionally enter the time quantum

Output Format

For each scheduling algorithm, the program shows:

1. Gantt Chart showing the execution sequence
2. Table with the following details for each process:
   • Process ID
   • Arrival Time (AT)
   • Burst Time (BT)
   • Completion Time (CT)
   • Turnaround Time (TAT)
   • Waiting Time (WT)
3. Average Waiting Time
4. Average Turnaround Time

Terms Used

• Arrival Time (AT): Time at which the process enters the ready queue
• Burst Time (BT): Total CPU time required by the process
• Completion Time (CT): Time at which process completes execution
• Turnaround Time (TAT): Total time taken from arrival to completion (CT - AT)
• Waiting Time (WT): Total time spent waiting in ready queue (TAT - BT)

Algorithms Implemented

1. First Come First Serve (FCFS)

   • Non-preemptive algorithm
   • Processes are executed in order of arrival

2. Shortest Job First (Non-Preemptive)

   • Non-preemptive algorithm
   • Process with shortest burst time is selected for execution
   • Process runs to completion once selected

3. Shortest Job First (Preemptive) / SRTF

   • Preemptive version of SJF
   • Current process can be preempted by a new process with shorter remaining time
   • Also known as Shortest Remaining Time First (SRTF)

4. Round Robin

   • Preemptive algorithm
   • Each process gets CPU for a fixed time quantum
   • After time quantum expires, process is moved to end of ready queue
   • Provides fair CPU sharing and good response time