FCFS_CPU_Scheduling.java

package java_algo;

import java.util.*;

public class FCFS_CPU_Scheduling {
	public static void main(String args[]) {
		Scanner sc = new Scanner(System.in);
		System.out.println("enter no of process: ");
		int n = sc.nextInt();
		int pid[] = new int[n]; // process ids
		int ar[] = new int[n]; // arrival times
		int bt[] = new int[n]; // burst or execution times
		int ct[] = new int[n]; // completion times
		int ta[] = new int[n]; // turn around times
		int wt[] = new int[n]; // waiting times
		int temp;
		float avgwt = 0, avgta = 0;

		for (int i = 0; i < n; i++) {
			System.out.println("enter process " + (i + 1) + " arrival time: ");
			ar[i] = sc.nextInt();
			System.out.println("enter process " + (i + 1) + " brust time: ");
			bt[i] = sc.nextInt();
			pid[i] = i + 1;
		}

//sorting according to arrival times
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < n - (i + 1); j++) {
				if (ar[j] > ar[j + 1]) {
					temp = ar[j];
					ar[j] = ar[j + 1];
					ar[j + 1] = temp;
					temp = bt[j];
					bt[j] = bt[j + 1];
					bt[j + 1] = temp;
					temp = pid[j];
					pid[j] = pid[j + 1];
					pid[j + 1] = temp;
				}
			}
		}
// finding completion times
		for (int i = 0; i < n; i++) {
			if (i == 0) {
				ct[i] = ar[i] + bt[i];
			} else {
				if (ar[i] > ct[i - 1]) {
					ct[i] = ar[i] + bt[i];
				} else
					ct[i] = ct[i - 1] + bt[i];
			}
			ta[i] = ct[i] - ar[i]; // turnaround time= completion time- arrival time
			wt[i] = ta[i] - bt[i]; // waiting time= turnaround time- burst time
			avgwt += wt[i]; // total waiting time
			avgta += ta[i]; // total turnaround time
		}
		System.out.println("\npid  arrival  brust  complete turn waiting");
		for (int i = 0; i < n; i++) {
			System.out.println(pid[i] + "  \t " + ar[i] + "\t" + bt[i] + "\t" + ct[i] + "\t" + ta[i] + "\t" + wt[i]);
		}
		sc.close();

		// Draw Gantt Chart
		System.out.println("Gantt Chart : ");
		for (int i = 0; i <= n; i++) {
			System.out.print(" ------");
		}


		System.out.println();
		for (int i = 0; i < n; i++) {
			System.out.print("|  P" + pid[i] + "  ");
		}
		System.out.print("|");
		System.out.println();

		System.out.print(0 + "------");
		for (int i = 0; i < n; i++) {

			
			System.out.print(ct[i] + "-----");
			
		}

		System.out.println("\naverage waiting time: " + (avgwt / n)); // printing average waiting time.
		System.out.println("average turnaround time:" + (avgta / n)); // printing average turnaround time.
	}
}