Write an Interview Experience

Round Robin Scheduling with different arrival times

Difficulty Level : Medium
Last Updated : 15 Feb, 2023

Read

Discuss(20+)

Prerequisite: Round Robin Scheduling with arrival time as 0

A round-robin scheduling algorithm is used to schedule the process fairly for each job a time slot or quantum and the interrupting the job if it is not completed by then the job come after the other job which is arrived in the quantum time that makes these scheduling fairly.

Note:

Round-robin is cyclic in nature, so starvation doesn’t occur
Round-robin is a variant of first come, first served scheduling
No priority, special importance is given to any process or task
RR scheduling is also known as Time slicing scheduling

Advantages:

Each process is served by CPU for a fixed time, so priority is the same for each one
Starvation does not occur because of its cyclic nature.

Disadvantages:

Throughput depends on quantum time.
If the time quantum is too large RR degrades to FCFS.
If we want to give some process priority, we cannot.

Process	Arrival Time	Burst Time	Completion time	Turn Around Time	Waiting time
P1	0	5	12	12	7
P2	1	4	11	10	6
P3	2	2	6	4	2
P4	3	1	9	6	5

Quantum time is 2 this means each process is only executing for 2 units of time at a time.
How to compute these process requests:-

Take the process which occurs first and start executing the process(for quantum time only).
Check if any other process request has arrived. If a process request arrives during the quantum time in which another process is executing, then add the new process to the Ready queue
After the quantum time has passed, check for any processes in the Ready queue. If the ready queue is empty then continue the current process. If the queue not empty and the current process is not complete, then add the current process to the end of the ready queue.
Take the first process from the Ready queue and start executing it (same rules)
Repeat all steps above from 2-4
If the process is complete and the ready queue is empty then the task is complete

After all these we get the three times which are:

Completion Time: the time taken for a process to complete.
Turn Around Time: total time the process exists in the system. (completion time – arrival time).
Waiting Time: total time waiting for their complete execution. (turn around time – burst time ).

How to implement in a programming language

1. Declare arrival[], burst[], wait[], turn[] arrays and initialize them. Also declare a timer
   variable and initialize it to zero. To sustain the original burst array create another 
   array (temp_burst[]) and copy all the values of burst array in it.
   
2. To keep a check we create another array of bool type which keeps the record of whether a
   process is completed or not. we also need to maintain a queue array which contains the process
   indices (initially the array is filled with 0).
   
3. Now we increment the timer variable until the first process arrives and when it does, we add the
   process index to the queue array 
   
4. Now we execute the first process until the time quanta and during that time quanta, we check 
   whether any other process has arrived or not and if it has then we add the index in the queue
   (by calling the fxn. queueUpdation()).
   
5. Now, after doing the above steps if a process has finished, we store its exit time and 
   execute the next process in the queue array. Else, we move the currently executed process at 
   the end of the queue (by calling another fxn. queueMaintainence()) when the time slice expires.
   
6. The above steps are then repeated until all the processes have been completely executed. If a
   scenario arises where there are some processes left but they have not arrived yet, then we
   shall wait and the CPU will remain idle during this interval.

Below is the implementation of the above approach:

(For the sake of simplicity, we assume that the arrival times are entered in a sorted way)
C++

C++

//C++ Program for implementing
//Round Robin Algorithm
//code by sparsh_cbs
#include <iostream>
 
using namespace std;
 
void queueUpdation(int queue[],int timer,int arrival[],int n, int maxProccessIndex){
    int zeroIndex;
    for(int i = 0; i < n; i++){
        if(queue[i] == 0){
            zeroIndex = i;
            break;
        }
    }   
    queue[zeroIndex] = maxProccessIndex + 1;
}
 
void queueMaintainence(int queue[], int n){
    for(int i = 0; (i < n-1) && (queue[i+1] != 0) ; i++){
        int temp = queue[i];
        queue[i] = queue[i+1];
        queue[i+1] = temp; 
    }
}
 
void checkNewArrival(int timer, int arrival[], int n, int maxProccessIndex,int queue[]){
    if(timer <= arrival[n-1]){
       bool newArrival = false;
       for(int j = (maxProccessIndex+1); j < n; j++){
             if(arrival[j] <= timer){
              if(maxProccessIndex < j){
                 maxProccessIndex = j;
                 newArrival = true;
              }
           }
       }
       //adds the incoming process to the ready queue
       //(if any arrives)
       if(newArrival)
          queueUpdation(queue,timer,arrival,n, maxProccessIndex);
    }
}
 
//Driver Code
int main(){
    int n,tq, timer = 0, maxProccessIndex = 0;
    float avgWait = 0, avgTT = 0;
    cout << "\nEnter the time quanta : ";
    cin>>tq;
    cout << "\nEnter the number of processes : ";
    cin>>n;
    int arrival[n], burst[n], wait[n], turn[n], queue[n], temp_burst[n];
    bool complete[n];
 
    cout << "\nEnter the arrival time of the processes : ";
    for(int i = 0; i < n; i++)
        cin>>arrival[i];
 
    cout << "\nEnter the burst time of the processes : ";
    for(int i = 0; i < n; i++){
        cin>>burst[i];
        temp_burst[i] = burst[i];
    }
 
    for(int i = 0; i < n; i++){    //Initializing the queue and complete array
        complete[i] = false;
        queue[i] = 0;
    }
    while(timer < arrival[0])    //Incrementing Timer until the first process arrives
        timer++; 
    queue[0] = 1;
     
    while(true){
        bool flag = true;
        for(int i = 0; i < n; i++){
            if(temp_burst[i] != 0){
                flag = false;
                break;
            }
        }
        if(flag)
            break;
 
        for(int i = 0; (i < n) && (queue[i] != 0); i++){
            int ctr = 0;
            while((ctr < tq) && (temp_burst[queue[0]-1] > 0)){
                temp_burst[queue[0]-1] -= 1;
                timer += 1;
                ctr++;
 
                //Checking and Updating the ready queue until all the processes arrive
                checkNewArrival(timer, arrival, n, maxProccessIndex, queue);
            }
            //If a process is completed then store its exit time
            //and mark it as completed
            if((temp_burst[queue[0]-1] == 0) && (complete[queue[0]-1] == false)){
                //turn array currently stores the completion time
                turn[queue[0]-1] = timer;        
                complete[queue[0]-1] = true;
            }
             
              //checks whether or not CPU is idle
            bool idle = true;
            if(queue[n-1] == 0){
                for(int i = 0; i < n && queue[i] != 0; i++){
                    if(complete[queue[i]-1] == false){
                        idle = false;
                    }
                }
            }
            else
                idle = false;
 
            if(idle){
                timer++;
                checkNewArrival(timer, arrival, n, maxProccessIndex, queue);
            }
       
            //Maintaining the entries of processes 
            //after each premption in the ready Queue
            queueMaintainence(queue,n);
        }
    }
 
    for(int i = 0; i < n; i++){
        turn[i] = turn[i] - arrival[i];
        wait[i] = turn[i] - burst[i];
    }
 
    cout << "\nProgram No.\tArrival Time\tBurst Time\tWait Time\tTurnAround Time"
         << endl;
    for(int i = 0; i < n; i++){
        cout<<i+1<<"\t\t"<<arrival[i]<<"\t\t"
          <<burst[i]<<"\t\t"<<wait[i]<<"\t\t"<<turn[i]<<endl;
    }
    for(int i =0; i< n; i++){
        avgWait += wait[i];
        avgTT += turn[i]; 
    }
    cout<<"\nAverage wait time : "<<(avgWait/n)
      <<"\nAverage Turn Around Time : "<<(avgTT/n);
 
    return 0;
     
}

Java

//JAVA Program for implementing
//Round Robin Algorithm
// code by Sparsh_cbs
import java.util.*;
 
public class RoundRobin{
    private static Scanner inp = new Scanner(System.in);
    //Driver Code
    public static void main(String[] args){
        int n,tq, timer = 0, maxProccessIndex = 0;
        float avgWait = 0, avgTT = 0;
        System.out.print("\nEnter the time quanta : ");
        tq = inp.nextInt();
        System.out.print("\nEnter the number of processes : ");
        n = inp.nextInt();
        int arrival[] = new int[n];
        int burst[] = new int[n];
        int wait[] = new int[n];
        int turn[] = new int[n];
        int queue[] = new int[n];
        int temp_burst[] = new int[n];
        boolean complete[] = new boolean[n];
 
        System.out.print("\nEnter the arrival time of the processes : ");
        for(int i = 0; i < n; i++)
            arrival[i] = inp.nextInt();
 
        System.out.print("\nEnter the burst time of the processes : ");
        for(int i = 0; i < n; i++){
            burst[i] = inp.nextInt();
            temp_burst[i] = burst[i];
        }
 
        for(int i = 0; i < n; i++){    //Initializing the queue and complete array
            complete[i] = false;
            queue[i] = 0;
        }
        while(timer < arrival[0])    //Incrementing Timer until the first process arrives
            timer++; 
        queue[0] = 1;
         
        while(true){
            boolean flag = true;
            for(int i = 0; i < n; i++){
                if(temp_burst[i] != 0){
                    flag = false;
                    break;
                }
            }
            if(flag)
                break;
 
            for(int i = 0; (i < n) && (queue[i] != 0); i++){
                int ctr = 0;
                while((ctr < tq) && (temp_burst[queue[0]-1] > 0)){
                    temp_burst[queue[0]-1] -= 1;
                    timer += 1;
                    ctr++;
 
                    //Updating the ready queue until all the processes arrive
                    checkNewArrival(timer, arrival, n, maxProccessIndex, queue);
                }
                if((temp_burst[queue[0]-1] == 0) && (complete[queue[0]-1] == false)){
                    turn[queue[0]-1] = timer;        //turn currently stores exit times
                    complete[queue[0]-1] = true;
                }
                 
                  //checks whether or not CPU is idle
                boolean idle = true;
                if(queue[n-1] == 0){
                    for(int k = 0; k < n && queue[k] != 0; k++){
                        if(complete[queue[k]-1] == false){
                            idle = false;
                        }
                    }
                }
                else
                    idle = false;
 
                if(idle){
                    timer++;
                    checkNewArrival(timer, arrival, n, maxProccessIndex, queue);
                }
               
                //Maintaining the entries of processes after each premption in the ready Queue
                queueMaintainence(queue,n);
            }
        }
 
        for(int i = 0; i < n; i++){
            turn[i] = turn[i] - arrival[i];
            wait[i] = turn[i] - burst[i];
        }
 
        System.out.print("\nProgram No.\tArrival Time\tBurst Time\tWait Time\tTurnAround Time"
                         + "\n");
        for(int i = 0; i < n; i++){
            System.out.print(i+1+"\t\t"+arrival[i]+"\t\t"+burst[i]
                             +"\t\t"+wait[i]+"\t\t"+turn[i]+ "\n");
        }
        for(int i =0; i< n; i++){
            avgWait += wait[i];
            avgTT += turn[i]; 
        }
        System.out.print("\nAverage wait time : "+(avgWait/n)
                         +"\nAverage Turn Around Time : "+(avgTT/n));
    }
    public static void queueUpdation(int queue[],int timer,int arrival[],int n, int maxProccessIndex){
        int zeroIndex = -1;
        for(int i = 0; i < n; i++){
            if(queue[i] == 0){
                zeroIndex = i;
                break;
            }
        }
        if(zeroIndex == -1)
            return;
        queue[zeroIndex] = maxProccessIndex + 1;
    }
 
    public static void checkNewArrival(int timer, int arrival[], int n, int maxProccessIndex,int queue[]){
        if(timer <= arrival[n-1]){
            boolean newArrival = false;
            for(int j = (maxProccessIndex+1); j < n; j++){
                if(arrival[j] <= timer){
                    if(maxProccessIndex < j){
                        maxProccessIndex = j;
                        newArrival = true;
                    }
                }
            }
            if(newArrival)    //adds the index of the arriving process(if any)
                queueUpdation(queue,timer,arrival,n, maxProccessIndex);        
        }
    }
   
    public static void queueMaintainence(int queue[], int n){
 
        for(int i = 0; (i < n-1) && (queue[i+1] != 0) ; i++){
            int temp = queue[i];
            queue[i] = queue[i+1];
            queue[i+1] = temp; 
        }
    }
}

Python3

# Python program for implementing Round Robin Algorithm
def queueUpdation(queue, timer, arrival, n, maxProccessIndex):
    zeroIndex = -1
    for i in range(n):
        if(queue[i] == 0):
            zeroIndex = i
            break
 
    if(zeroIndex == -1):
        return
    queue[zeroIndex] = maxProccessIndex + 1
 
 
def checkNewArrival(timer, arrival, n, maxProccessIndex, queue):
    if(timer <= arrival[n-1]):
        newArrival = False
        for j in range(maxProccessIndex+1, n):
            if(arrival[j] <= timer):
                if(maxProccessIndex < j):
                    maxProccessIndex = j
                    newArrival = True
 
        # adds the index of the arriving process(if any)
        if(newArrival):
            queueUpdation(queue, timer, arrival, n, maxProccessIndex)
 
 
def queueMaintainence(queue, n):
    for i in range(n-1):
        if(queue[i+1] != 0):
            queue[i], queue[i+1] = queue[i+1], queue[i]
 
 
timer, maxProccessIndex = 0, 0
avgWait, avgTT = 0, 0
print("\nEnter the time quanta :", end=" ")
tq = int(input())
print("\nEnter the number of processes :", end=" ")
n = int(input())
arrival = [0]*n
burst = [0]*n
wait = [0]*n
turn = [0]*n
queue = [0]*n
temp_burst = [0]*n
complete = [False]*n
print("\nEnter the arrival time of the processes :", end=" ")
for i in range(n):
    arrival[i] = int(input())
 
print("\nEnter the burst time of the processes :", end=" ")
for i in range(n):
    burst[i] = int(input())
    temp_burst[i] = burst[i]
 
for i in range(n):
        # Initializing the queue and complete array
    complete[i] = False
    queue[i] = 0
 
while(timer < arrival[0]):
        # Incrementing Timer until the first process arrives
    timer += 1
queue[0] = 1
 
while(True):
    flag = True
    for i in range(n):
        if(temp_burst[i] != 0):
            flag = False
            break
 
    if(flag):
        break
 
    for i in range(n and queue[i] != 0):
        ctr = 0
        while((ctr < tq) and (temp_burst[queue[0]-1] > 0)):
            temp_burst[queue[0]-1] -= 1
            timer += 1
            ctr += 1
 
            # Updating the ready queue until all the processes arrive
            checkNewArrival(timer, arrival, n, maxProccessIndex, queue)
 
        if((temp_burst[queue[0]-1] == 0) and (complete[queue[0]-1] == False)):
            # turn currently stores exit times
            turn[queue[0]-1] = timer
            complete[queue[0]-1] = True
 
        # checks whether or not CPU is idle
        idle = True
        if(queue[n-1] == 0):
            for k in range(n):
                if(queue[k] != 0):
                    if(complete[queue[k]-1] == False):
                        idle = False
        else:
            idle = False
 
        if(idle):
            timer += 1
            checkNewArrival(timer, arrival, n, maxProccessIndex, queue)
 
        # Maintaining the entries of processes aftereach premption in the ready Queue
        queueMaintainence(queue, n)
 
for i in range(n):
    turn[i] = turn[i] - arrival[i]
    wait[i] = turn[i] - burst[i]
 
print("\nProgram No.\tArrival Time\tBurst Time\tWait Time\tTurnAround Time\n")
 
for i in range(n):
    print(i+1, "\t\t", arrival[i], "\t\t", burst[i],
          "\t\t", wait[i], "\t\t", turn[i], "\n")
 
for i in range(n):
    avgWait += wait[i]
    avgTT += turn[i]
 
print("\nAverage wait time : ", (avgWait//n))
print("\nAverage Turn Around Time : ", (avgTT//n))
 
# This code is contributed by lokeshmvs21.

C#

// C# program to implement Round Robin
// Scheduling with different arrival time
using System;
 
class GFG {
    public static void roundRobin(String[] p, int[] a,
                                  int[] b, int n)
    {
        // result of average times
        int res = 0;
        int resc = 0;
 
        // for sequence storage
        String seq = "";
 
        // copy the burst array and arrival array
        // for not effecting the actual array
        int[] res_b = new int[b.Length];
        int[] res_a = new int[a.Length];
 
        for (int i = 0; i < res_b.Length; i++) {
            res_b[i] = b[i];
            res_a[i] = a[i];
        }
 
        // critical time of system
        int t = 0;
 
        // for store the waiting time
        int[] w = new int[p.Length];
 
        // for store the Completion time
        int[] comp = new int[p.Length];
 
        while (true) {
            Boolean flag = true;
            for (int i = 0; i < p.Length; i++) {
 
                // these condition for if
                // arrival is not on zero
 
                // check that if there come before qtime
                if (res_a[i] <= t) {
                    if (res_a[i] <= n) {
                        if (res_b[i] > 0) {
                            flag = false;
                            if (res_b[i] > n) {
 
                                // make decrease the b time
                                t = t + n;
                                res_b[i] = res_b[i] - n;
                                res_a[i] = res_a[i] + n;
                                seq += "->" + p[i];
                            }
                            else {
 
                                // for last time
                                t = t + res_b[i];
 
                                // store comp time
                                comp[i] = t - a[i];
 
                                // store wait time
                                w[i] = t - b[i] - a[i];
                                res_b[i] = 0;
 
                                // add sequence
                                seq += "->" + p[i];
                            }
                        }
                    }
                    else if (res_a[i] > n) {
 
                        // is any have less arrival time
                        // the coming process then execute
                        // them
                        for (int j = 0; j < p.Length; j++) {
 
                            // compare
                            if (res_a[j] < res_a[i]) {
                                if (res_b[j] > 0) {
                                    flag = false;
                                    if (res_b[j] > n) {
                                        t = t + n;
                                        res_b[j]
                                            = res_b[j] - n;
                                        res_a[j]
                                            = res_a[j] + n;
                                        seq += "->" + p[j];
                                    }
                                    else {
                                        t = t + res_b[j];
                                        comp[j] = t - a[j];
                                        w[j] = t - b[j]
                                               - a[j];
                                        res_b[j] = 0;
                                        seq += "->" + p[j];
                                    }
                                }
                            }
                        }
 
                        // now the previous process
                        // according to ith is process
                        if (res_b[i] > 0) {
                            flag = false;
 
                            // Check for greaters
                            if (res_b[i] > n) {
                                t = t + n;
                                res_b[i] = res_b[i] - n;
                                res_a[i] = res_a[i] + n;
                                seq += "->" + p[i];
                            }
                            else {
                                t = t + res_b[i];
                                comp[i] = t - a[i];
                                w[i] = t - b[i] - a[i];
                                res_b[i] = 0;
                                seq += "->" + p[i];
                            }
                        }
                    }
                }
 
                // if no process is come on the critical
                else if (res_a[i] > t) {
                    t++;
                    i--;
                }
            }
 
            // for exit the while loop
            if (flag) {
                break;
            }
        }
 
        Console.WriteLine("name   ctime   wtime");
        for (int i = 0; i < p.Length; i++) {
            Console.WriteLine(" " + p[i] + "\t" + comp[i]
                              + "\t" + w[i]);
 
            res = res + w[i];
            resc = resc + comp[i];
        }
 
        Console.WriteLine("Average waiting time is "
                          + (float)res / p.Length);
        Console.WriteLine("Average compilation time is "
                          + (float)resc / p.Length);
        Console.WriteLine("Sequence is like that " + seq);
    }
 
    // Driver Code
    public static void Main(String[] args)
    {
        // name of the process
        String[] name = { "p1", "p2", "p3", "p4" };
 
        // arrival for every process
        int[] arrivaltime = { 0, 1, 2, 3 };
 
        // burst time for every process
        int[] bursttime = { 10, 4, 5, 3 };
 
        // quantum time of each process
        int q = 3;
 
        // cal the function for output
        roundRobin(name, arrivaltime, bursttime, q);
    }
}
 
// This code is contributed by Rajput-Ji

Javascript

<script>
 
const queueUpdation = (queue, timer, arrival, n, maxProccessIndex) => {
            let zeroIndex;
            for (let i = 0; i < n; i++) {
                if (queue[i] == 0) {
                    zeroIndex = i;
                    break;
                }
            }
            queue[zeroIndex] = maxProccessIndex + 1;
        }
 
        const queueMaintainence = (queue, n) => {
            for (let i = 0; (i < n - 1) && (queue[i + 1] != 0); i++) {
                let temp = queue[i];
                queue[i] = queue[i + 1];
                queue[i + 1] = temp;
            }
        }
 
        const checkNewArrival = (timer, arrival, n, maxProccessIndex, queue) => {
            if (timer <= arrival[n - 1]) {
                let newArrival = false;
                for (let j = (maxProccessIndex + 1); j < n; j++) {
                    if (arrival[j] <= timer) {
                        if (maxProccessIndex < j) {
                            maxProccessIndex = j;
                            newArrival = true;
                        }
                    }
                }
                //adds the incoming process to the ready queue
                //(if any arrives)
                if (newArrival)
                    queueUpdation(queue, timer, arrival, n, maxProccessIndex);
            }
        }
 
        //Driver Code
        let n = 4;
        let tq = 2;
        let timer = 0;
        let maxProccessIndex = 0;
        let avgWait = 0;
        let avgTT = 0;
        const wait = [];
        const turn = [];
        const queue = [];
        const temp_burst = [];
        const complete = [];
        const arrival = [0, 1, 2, 3];
        const burst = [5, 4, 2, 1];
 
        for (let i = 0; i < n; i++) {
            temp_burst[i] = burst[i];
        }
 
        for (let i = 0; i < n; i++) {    //Initializing the queue and complete array
            complete[i] = false;
            queue[i] = 0;
        }
        while (timer < arrival[0])    //Incrementing Timer until the first process arrives
            timer++;
        queue[0] = 1;
 
        while (true) {
        let flag = true;
            for (let i = 0; i < n; i++) {
                if (temp_burst[i] != 0) {
                    flag = false;
                    break;
                }
            }
            if (flag)
                break;
 
            for (let i = 0; (i < n) && (queue[i] != 0); i++) {
                let ctr = 0;
                while ((ctr < tq) && (temp_burst[queue[0] - 1] > 0)) {
                    temp_burst[queue[0] - 1] -= 1;
                    timer += 1;
                    ctr++;
 
                    // Checking and Updating the ready queue until all the processes arrive
                    checkNewArrival(timer, arrival, n, maxProccessIndex, queue);
                }
                // If a process is completed then store its exit time
                // and mark it as completed
                if ((temp_burst[queue[0] - 1] == 0) && (complete[queue[0] - 1] == false)) {
                    //turn array currently stores the completion time
                    turn[queue[0] - 1] = timer;
                    complete[queue[0] - 1] = true;
                }
 
                // checks whether or not CPU is idle
                let idle = true;
                if (queue[n - 1] == 0) {
                    for (let i = 0; i < n && queue[i] != 0; i++) {
                        if (complete[queue[i] - 1] == false) {
                            idle = false;
                        }
                    }
                }
                else
                    idle = false;
 
                if (idle) {
                    timer++;
                    checkNewArrival(timer, arrival, n, maxProccessIndex, queue);
                }
 
                //Maintaining the entries of processes 
                //after each premption in the ready Queue
                queueMaintainence(queue, n);
            }
        }
 
        for (let i = 0; i < n; i++) {
            turn[i] = turn[i] - arrival[i];
            wait[i] = turn[i] - burst[i];
        }
 
        console.log(`Time Quanta : ${tq}`);
        console.log(`Number of Processes : ${n}`);
        console.log(`Arrival Time of Processes : ${arrival}`);
        console.log(`Burst Time of Processes : ${burst}`);
 
        console.log("\nProgram No.\tArrival Time\tBurst Time\tWait Time\tTurnAround Time\n");
        for (let i = 0; i < n; i++) {
            console.log(`${i + 1}\t\t\t ${arrival[i]}\t\t\t ${burst[i]}\t\t\t\t ${wait[i]} \t\t\t\t ${turn[i]} \n`);
        }
        for (let i = 0; i < n; i++) {
            avgWait += wait[i];
            avgTT += turn[i];
        }
        console.log(`\nAverage wait time : ${avgWait / n}`);
        console.log(`\nAverage Turn Around Time : ${avgTT / n}`);
 
// This code is contributed by akashish_.
 
</script>

Output:

Enter the time quanta : 2

Enter the number of processes : 4

Enter the arrival time of the processes : 0 1 2 3

Enter the burst time of the processes : 5 4 2 1

Program No.     Arrival Time    Burst Time      Wait Time       TurnAround Time
1               0               5               7               12
2               1               4               6               10
3               2               2               2               4
4               3               1               5               6

Average wait time : 5
Average Turn Around Time : 8

In case of any queries or a problem with the code, please write it in the comment section.

Note: A slightly optimized version of the above-implemented code could be done by using Queue data structure as follows:

C++

#include <bits/stdc++.h>
 
using namespace std;
 
struct Process
{
    int pid;
    int arrivalTime;
    int burstTime;
    int burstTimeRemaining; // the amount of CPU time remaining after each execution
    int completionTime;
    int turnaroundTime;
    int waitingTime;
    bool isComplete;
    bool inQueue;
};
 
/*
 * At every time quantum or when a process has been executed before the time quantum,
 * check for any new arrivals and push them into the queue
*/
void checkForNewArrivals(Process processes[], const int n, const int currentTime, queue<int> &readyQueue)
{
    for (int i = 0; i < n; i++)
    {
        Process p = processes[i];
        // checking if any processes has arrived
        // if so, push them in the ready Queue.
        if (p.arrivalTime <= currentTime && !p.inQueue && !p.isComplete)
        {
            processes[i].inQueue = true;
            readyQueue.push(i);
        }
    }
}
 
/*
 * Context switching takes place at every time quantum
 * At every iteration, the burst time of the processes in the queue are handled using this method
*/
void updateQueue(Process processes[], const int n, const int quantum, queue<int> &readyQueue, int ¤tTime, int &programsExecuted)
{
    int i = readyQueue.front();
    readyQueue.pop();
 
    // if the process is going to be finished executing, 
    // ie, when it's remaining burst time is less than time quantum
    // mark it completed and increment the current time
    // and calculate its waiting time and turnaround time
    if (processes[i].burstTimeRemaining <= quantum)
    {
        processes[i].isComplete = true;
        currentTime += processes[i].burstTimeRemaining;
        processes[i].completionTime = currentTime;
        processes[i].waitingTime = processes[i].completionTime - processes[i].arrivalTime - processes[i].burstTime;
        processes[i].turnaroundTime = processes[i].waitingTime + processes[i].burstTime;
 
        if (processes[i].waitingTime < 0)
            processes[i].waitingTime = 0;
 
        processes[i].burstTimeRemaining = 0;
 
        // if all the processes are not yet inserted in the queue,
        // then check for new arrivals
        if (programsExecuted != n)
        {
            checkForNewArrivals(processes, n, currentTime, readyQueue);
        }
    }
    else
    {
        // the process is not done yet. But it's going to be pre-empted 
        // since one quantum is used
        // but first subtract the time the process used so far
        processes[i].burstTimeRemaining -= quantum;
        currentTime += quantum;
 
        // if all the processes are not yet inserted in the queue,
        // then check for new arrivals
        if (programsExecuted != n)
        {
            checkForNewArrivals(processes, n, currentTime, readyQueue);
        }
        // insert the incomplete process back into the queue
        readyQueue.push(i);
    }
}
 
/*
 * Just a function that outputs the result in terms of their PID.
*/
void output(Process processes[], const int n)
{
    double avgWaitingTime = 0;
    double avgTurntaroundTime = 0;
    // sort the processes array by processes.PID
    sort(processes, processes + n, [](const Process &p1, const Process &p2)
         { return p1.pid < p2.pid; });
 
    for (int i = 0; i < n; i++)
    {
        cout << "Process " << processes[i].pid << ": Waiting Time: " << processes[i].waitingTime << " Turnaround Time: " << processes[i].turnaroundTime << endl;
        avgWaitingTime += processes[i].waitingTime;
        avgTurntaroundTime += processes[i].turnaroundTime;
    }
    cout << "Average Waiting Time: " << avgWaitingTime / n << endl;
    cout << "Average Turnaround Time: " << avgTurntaroundTime / n << endl;
}
 
/* 
 * This function assumes that the processes are already sorted according to their arrival time
 */
void roundRobin(Process processes[], int n, int quantum)
{
    queue<int> readyQueue;
    readyQueue.push(0); // initially, pushing the first process which arrived first
    processes[0].inQueue = true;
   
    int currentTime = 0; // holds the current time after each process has been executed
    int programsExecuted = 0; // holds the number of programs executed so far
 
    while (!readyQueue.empty())
    {
        updateQueue(processes, n, quantum, readyQueue, currentTime, programsExecuted);
    }
}
 
int main()
{
    int n, quantum;
 
    cout << "Enter the number of processes: ";
    cin >> n;
    cout << "Enter time quantum: ";
    cin >> quantum;
 
    Process processes[n + 1];
 
    for (int i = 0; i < n; i++)
    {
        cout << "Enter arrival time and burst time of each process " << i + 1 << ": ";
        cin >> processes[i].arrivalTime;
        cin >> processes[i].burstTime;
        processes[i].burstTimeRemaining = processes[i].burstTime;
        processes[i].pid = i + 1;
        cout << endl;
    }
 
    // stl sort in terms of arrival time
    sort(processes, processes + n, [](const Process &p1, const Process &p2)
         { return p1.arrivalTime < p2.arrivalTime; });
 
    roundRobin(processes, n, quantum);
 
    output(processes, n);
 
    return 0;
}

Java

// Java Code
import java.util.Arrays;
import java.util.LinkedList;
import java.util.Queue;
 
class GFG {
 
  // At every time quantum or when a process has been
  // executed before the time quantum, check for any new
  // arrivals and push them into the queue
  public static void
    checkForNewArrivals(Process[] processes, int n,
                        int currentTime,
                        Queue<Integer> readyQueue)
  {
    for (int i = 0; i < n; i++) {
      Process p = processes[i];
      // checking if any processes has arrived
      // if so, push them in the ready Queue.
      if (p.arrivalTime <= currentTime && !p.inQueue
          && !p.isComplete) {
        processes[i].inQueue = true;
        readyQueue.add(i);
      }
    }
  }
 
  // Context switching takes place at every time quantum
  // At every iteration, the burst time of the processes
  // in the queue are handled using this method
  public static void
    updateQueue(Process[] processes, int n, int quantum,
                Queue<Integer> readyQueue, int currentTime,
                int programsExecuted)
  {
    int i = readyQueue.remove();
 
    // if the process is going to be finished executing,
    // ie, when it's remaining burst time is less than
    // time quantum mark it completed and increment the
    // current time and calculate its waiting time and
    // turnaround time
    if (processes[i].burstTimeRemaining <= quantum) {
      processes[i].isComplete = true;
      currentTime += processes[i].burstTimeRemaining;
      processes[i].completionTime = currentTime;
      processes[i].waitingTime
        = processes[i].completionTime
        - processes[i].arrivalTime
        - processes[i].burstTime;
      processes[i].turnaroundTime
        = processes[i].waitingTime
        + processes[i].burstTime;
 
      if (processes[i].waitingTime < 0)
        processes[i].waitingTime = 0;
 
      processes[i].burstTimeRemaining = 0;
 
      // if all the processes are not yet inserted in
      // the queue, then check for new arrivals
      if (programsExecuted != n) {
        checkForNewArrivals(
          processes, n, currentTime, readyQueue);
      }
    }
    else {
      // the process is not done yet. But it's going
      // to be pre-empted since one quantum is used
      // but first subtract the time the process used
      // so far
      processes[i].burstTimeRemaining -= quantum;
      currentTime += quantum;
 
      // if all the processes are not yet inserted in
      // the queue, then check for new arrivals
      if (programsExecuted != n) {
        checkForNewArrivals(
          processes, n, currentTime, readyQueue);
      }
      // insert the incomplete process back into the
      // queue
      readyQueue.add(i);
    }
  }
 
  // Just a function that outputs the result in terms of
  // their PID.
  public static void output(Process[] processes, int n)
  {
    double avgWaitingTime = 0;
    double avgTurntaroundTime = 0;
    // sort the processes array by processes.PID
    Arrays.sort(processes, (Process p1, Process p2) -> {
      return p1.pid - p2.pid;
    });
 
    for (int i = 0; i < n; i++) {
      System.out.println(
        "Process " + processes[i].pid
        + ": Waiting Time: "
        + processes[i].waitingTime
        + " Turnaround Time: "
        + processes[i].turnaroundTime);
      avgWaitingTime += processes[i].waitingTime;
      avgTurntaroundTime
        += processes[i].turnaroundTime;
    }
    System.out.println("Average Waiting Time: "
                       + avgWaitingTime / n);
    System.out.println("Average Turnaround Time: "
                       + avgTurntaroundTime / n);
  }
 
  /*
     * This function assumes that the processes are already
     * sorted according to their arrival time
     */
  public static void roundRobin(Process[] processes,
                                int n, int quantum)
  {
    Queue<Integer> readyQueue
      = new LinkedList<Integer>();
    readyQueue.add(0); // initially, pushing the first
    // process which arrived first
    processes[0].inQueue = true;
 
    int currentTime
      = 0; // holds the current time after each
    // process has been executed
    int programsExecuted
      = 0; // holds the number of programs executed so
    // far
 
    while (!readyQueue.isEmpty()) {
      updateQueue(processes, n, quantum, readyQueue,
                  currentTime, programsExecuted);
    }
  }
 
  public static class Process {
    int pid;
    int arrivalTime;
    int burstTime;
    int burstTimeRemaining; // the amount of CPU time
    // remaining after each
    // execution
    int completionTime;
    int turnaroundTime;
    int waitingTime;
    boolean isComplete;
    boolean inQueue;
  }
 
  public static void main(String[] args)
  {
    int n, quantum;
 
    System.out.println(
      "Enter the number of processes: ");
    n = Integer.parseInt(System.console().readLine());
    System.out.println("Enter time quantum: ");
    quantum
      = Integer.parseInt(System.console().readLine());
 
    Process[] processes = new Process[n + 1];
 
    for (int i = 0; i < n; i++) {
      System.out.println(
        "Enter arrival time and burst time of each process "
        + (i + 1) + ": ");
      processes[i].arrivalTime = Integer.parseInt(
        System.console().readLine());
      processes[i].burstTime = Integer.parseInt(
        System.console().readLine());
      processes[i].burstTimeRemaining
        = processes[i].burstTime;
      processes[i].pid = i + 1;
      System.out.println();
    }
 
    // stl sort in terms of arrival time
    Arrays.sort(processes, (Process p1, Process p2) -> {
      return p1.arrivalTime - p2.arrivalTime;
    });
 
    roundRobin(processes, n, quantum);
 
    output(processes, n);
  }
}
 
// This code is contributed by akashish__

Python3

# Python Code
class Process:
    def __init__(self):
        self.pid = 0
        self.arrivalTime = 0
        self.burstTime = 0
        self.burstTimeRemaining = 0
        self.completionTime = 0
        self.turnaroundTime = 0
        self.waitingTime = 0
        self.isComplete = False
        self.inQueue = False
 
# At every time quantum or when a process has been executed before the time quantum,
# check for any new arrivals and push them into the queue
def check_for_new_arrivals(processes, n, current_time, ready_queue):
    for i in range(n):
        p = processes[i]
        # checking if any processes has arrived
        # if so, push them in the ready Queue.
        if p.arrivalTime <= current_time and not p.inQueue and not p.isComplete:
            processes[i].inQueue = True
            ready_queue.append(i)
 
# Context switching takes place at every time quantum
# At every iteration, the burst time of the processes in the queue are handled using this method
def update_queue(processes, n, quantum, ready_queue, current_time, programs_executed):
    i = ready_queue[0]
    ready_queue.pop(0)
 
    # if the process is going to be finished executing,
    # ie, when it's remaining burst time is less than time quantum
    # mark it completed and increment the current time
    # and calculate its waiting time and turnaround time
    if processes[i].burstTimeRemaining <= quantum:
        processes[i].isComplete = True
        current_time += processes[i].burstTimeRemaining
        processes[i].completionTime = current_time
        processes[i].waitingTime = processes[i].completionTime - processes[i].arrivalTime - processes[i].burstTime
        processes[i].turnaroundTime = processes[i].waitingTime + processes[i].burstTime
 
        if processes[i].waitingTime < 0:
            processes[i].waitingTime = 0
 
        processes[i].burstTimeRemaining = 0
 
        # if all the processes are not yet inserted in the queue,
        # then check for new arrivals
        if programs_executed != n:
            check_for_new_arrivals(processes, n, current_time, ready_queue)
    else:
        # the process is not done yet. But it's going to be pre-empted
        # since one quantum is used
        # but first subtract the time the process used so far
        processes[i].burstTimeRemaining -= quantum
        current_time += quantum
 
        # if all the processes are not yet inserted in the queue,
        # then check for new arrivals
        if programs_executed != n:
            check_for_new_arrivals(processes, n, current_time, ready_queue)
        # insert the incomplete process back into the queue
        ready_queue.append(i)
 
# Just a function that outputs the result in terms of their PID.
def output(processes, n):
    avg_waiting_time = 0
    avg_turntaround_time = 0
    # sort the processes array by processes.PID
    processes.sort(key=lambda p: p.pid)
 
    for i in range(n):
        print("Process ", processes[i].pid, ": Waiting Time: ", processes[i].waitingTime,
              " Turnaround Time: ", processes[i].turnaroundTime, sep="")
        avg_waiting_time += processes[i].waitingTime
        avg_turntaround_time += processes[i].turnaroundTime
    print("Average Waiting Time: ", avg_waiting_time / n)
    print("Average Turnaround Time: ", avg_turntaround_time / n)
 
# This function assumes that the processes are already sorted according to their arrival time
def round_robin(processes, n, quantum):
    ready_queue = []
    ready_queue.append(0) # initially, pushing the first process which arrived first
    processes[0].inQueue = True
 
    current_time = 0 # holds the current time after each process has been executed
    programs_executed = 0 # holds the number of programs executed so far
 
    while len(ready_queue) != 0:
        update_queue(processes, n, quantum, ready_queue, current_time, programs_executed)
 
def main():
    n = int(input("Enter the number of processes: "))
    quantum = int(input("Enter time quantum: "))
 
    processes = []
 
    for i in range(n):
        print("Enter arrival time and burst time of each process ", i + 1, ": ", sep="", end="")
        arrival_time = int(input())
        burst_time = int(input())
        proc = Process()
        proc.arrivalTime = arrival_time
        proc.burstTime = burst_time
        proc.burstTimeRemaining = burst_time
        proc.pid = i + 1
        processes.append(proc)
        print("")
 
    # stl sort in terms of arrival time
    processes.sort(key=lambda p: p.arrivalTime)
 
    round_robin(processes, n, quantum)
 
    output(processes, n)
 
main()
 
# This code is contributed by akashish__

C#

// C# Code
using System;
using System.Collections.Generic;
using System.Linq;
 
class GFG 
{ 
    // At every time quantum or when a process has been 
    // executed before the time quantum, check for any new 
    // arrivals and push them into the queue 
    public static void
        checkForNewArrivals(Process[] processes, int n, 
                            int currentTime, 
                            Queue<int> readyQueue) 
    { 
        for (int i = 0; i < n; i++) 
        { 
            Process p = processes[i]; 
            // checking if any processes has arrived 
            // if so, push them in the ready Queue. 
            if (p.arrivalTime <= currentTime && !p.inQueue 
                && !p.isComplete) 
            { 
                processes[i].inQueue = true; 
                readyQueue.Enqueue(i); 
            } 
        } 
    } 
   
    // Context switching takes place at every time quantum 
    // At every iteration, the burst time of the processes 
    // in the queue are handled using this method 
    public static void
        updateQueue(Process[] processes, int n, int quantum, 
                    Queue<int> readyQueue, int currentTime, 
                    int programsExecuted) 
    { 
        int i = readyQueue.Dequeue(); 
   
        // if the process is going to be finished executing, 
        // ie, when it's remaining burst time is less than 
        // time quantum mark it completed and increment the 
        // current time and calculate its waiting time and 
        // turnaround time 
        if (processes[i].burstTimeRemaining <= quantum) 
        { 
            processes[i].isComplete = true; 
            currentTime += processes[i].burstTimeRemaining; 
            processes[i].completionTime = currentTime; 
            processes[i].waitingTime 
                = processes[i].completionTime 
                - processes[i].arrivalTime 
                - processes[i].burstTime; 
            processes[i].turnaroundTime 
                = processes[i].waitingTime 
                + processes[i].burstTime; 
   
            if (processes[i].waitingTime < 0) 
                processes[i].waitingTime = 0; 
   
            processes[i].burstTimeRemaining = 0; 
   
            // if all the processes are not yet inserted in 
            // the queue, then check for new arrivals 
            if (programsExecuted != n) 
            { 
                checkForNewArrivals( 
                    processes, n, currentTime, readyQueue); 
            } 
        } 
        else
        { 
            // the process is not done yet. But it's going 
            // to be pre-empted since one quantum is used 
            // but first subtract the time the process used 
            // so far 
            processes[i].burstTimeRemaining -= quantum; 
            currentTime += quantum; 
   
            // if all the processes are not yet inserted in 
            // the queue, then check for new arrivals 
            if (programsExecuted != n) 
            { 
                checkForNewArrivals( 
                    processes, n, currentTime, readyQueue); 
            } 
            // insert the incomplete process back into the 
            // queue 
            readyQueue.Enqueue(i); 
        } 
    } 
   
    // Just a function that outputs the result in terms of 
    // their PID. 
    public static void output(Process[] processes, int n) 
    { 
        double avgWaitingTime = 0; 
        double avgTurntaroundTime = 0; 
        // sort the processes array by processes.PID 
        processes = processes.OrderBy(p => p.pid).ToArray();
   
        for (int i = 0; i < n; i++) 
        { 
            Console.WriteLine("Process " + processes[i].pid 
                              + ": Waiting Time: "
                              + processes[i].waitingTime 
                              + " Turnaround Time: "
                              + processes[i].turnaroundTime); 
            avgWaitingTime += processes[i].waitingTime; 
            avgTurntaroundTime 
                += processes[i].turnaroundTime; 
        } 
        Console.WriteLine("Average Waiting Time: "
                          + avgWaitingTime / n); 
        Console.WriteLine("Average Turnaround Time: "
                          + avgTurntaroundTime / n); 
    } 
   
    /*
     * This function assumes that the processes are already
     * sorted according to their arrival time
     */
    public static void roundRobin(Process[] processes, 
                                  int n, int quantum) 
    { 
        Queue<int> readyQueue 
            = new Queue<int>(); 
        readyQueue.Enqueue(0); // initially, pushing the first 
        // process which arrived first 
        processes[0].inQueue = true; 
   
        int currentTime 
            = 0; // holds the current time after each 
        // process has been executed 
        int programsExecuted 
            = 0; // holds the number of programs executed so 
        // far 
   
        while (readyQueue.Count() > 0) 
        { 
            updateQueue(processes, n, quantum, readyQueue, 
                        currentTime, programsExecuted); 
        } 
    } 
   
    public class Process 
    { 
        public int pid; 
        public int arrivalTime; 
        public int burstTime; 
        public int burstTimeRemaining; // the amount of CPU time 
        // remaining after each 
        // execution 
        public int completionTime; 
        public int turnaroundTime; 
        public int waitingTime; 
        public bool isComplete; 
        public bool inQueue; 
    } 
   
    public static void Main(String[] args) 
    { 
        int n, quantum; 
   
        Console.WriteLine("Enter the number of processes: "); 
        n = int.Parse(Console.ReadLine()); 
        Console.WriteLine("Enter time quantum: "); 
        quantum 
            = int.Parse(Console.ReadLine()); 
   
        Process[] processes = new Process[n + 1]; 
   
        for (int i = 0; i < n; i++) 
        { 
            Console.WriteLine("Enter arrival time and burst time of each process "
                              + (i + 1) + ": "); 
            processes[i].arrivalTime = int.Parse( 
                Console.ReadLine()); 
            processes[i].burstTime = int.Parse( 
                Console.ReadLine()); 
            processes[i].burstTimeRemaining 
                = processes[i].burstTime; 
            processes[i].pid = i + 1; 
            Console.WriteLine(); 
        } 
   
        // stl sort in terms of
      processes.OrderBy(p => p.arrivalTime).ToArray();
      roundRobin(processes, n, quantum);
 
    output(processes, n);
  }
}
 
// This code is contributed by akashish__

Enter the number of processes: 4

Enter time quantum: 2

Enter the arrival time and burst time of each process: 
0 5
1 4
2 2
3 1

Process 1: Waiting Time: 7 Turnaround Time: 12
Process 2: Waiting Time: 6 Turnaround Time: 10
Process 3: Waiting Time: 2 Turnaround Time: 4
Process 4: Waiting Time: 5 Turnaround Time: 6

Average Waiting Time: 5
Average Turnaround Time: 8

My Personal Notes