Program for Round Robin Scheduling for the same Arrival time

Round Robin is a CPU scheduling algorithm where each process is assigned a fixed time slot in a cyclic way. It is basically the preemptive version of First come First Serve CPU Scheduling algorithm. 

• Round Robin CPU Algorithm generally focuses on Time Sharing technique. 
• The period of time for which a process or job is allowed to run in a pre-emptive method is called time quantum. 
• Each process or job present in the ready queue is assigned the CPU for that time quantum, if the execution of the process is completed during that time then the process will end else the process will go back to the waiting table and wait for its next turn to complete the execution.
  

Characteristics of Round Robin CPU Scheduling Algorithm

• It is simple, easy to implement, and starvation-free as all processes get fair share of CPU.
• One of the most commonly used technique in CPU scheduling as a core.
• It is preemptive as processes are assigned CPU only for a fixed slice of time at most.
• The disadvantage of it is more overhead of context switching.

Advantages of Round Robin CPU Scheduling Algorithm

• There is fairness since every process gets equal share of CPU.
• The newly created process is added to end of ready queue.
• A round-robin scheduler generally employs time-sharing, giving each job a time slot or quantum. 
• While performing a round-robin scheduling, a particular time quantum is allotted to different jobs. 
• Each process get a chance to reschedule after a particular quantum time in this scheduling. 

Disadvantages of Round Robin CPU Scheduling Algorithm

• There is Larger waiting time and Response time.
• There is Low throughput.
• There is Context Switches.
• Gantt chart seems to come too big (if quantum time is less for scheduling. For Example:1 ms for big scheduling.)
• Time consuming scheduling for small quantum.

Examples to show working of Round Robin Scheduling Algorithm

Example-1: Consider the following table of arrival time and burst time for four processes P1, P2, P3, and P4 and given Time Quantum = 2

Process	Burst Time	Arrival Time
P1	5 ms	0 ms
P2	4 ms	1 ms
P3	2 ms	2 ms
P4	1 ms	4 ms

The Round Robin CPU Scheduling Algorithm will work on the basis of steps as mentioned below:

At time = 0,

• The execution begins with process P1, which has burst time 5. 
• Here, every process executes for 2 milliseconds (Time Quantum Period). P2 and P3 are still in the waiting queue.

Time Instance	Process	Arrival Time	Ready Queue	Running Queue	Execution Time	Initial Burst Time	Remaining Burst  Time
0-2ms	P1	0ms	P2, P3	P1	2ms	5ms	3ms

At time = 2,

• The processes P2 and P3 arrives in the ready queue and P2 starts executing for TQ period

Time Instance	Process	Arrival Time	Ready Queue	Running Queue	Execution Time	Initial Burst Time	Remaining Burst  Time
2-4ms	P1	0ms	P3, P1	P2	0ms	3ms	3ms
	P2	1ms			2ms	4ms	2ms

At time = 4,

• The process P4 arrives in the ready queue, 
• Then P3 executes for TQ period.

Time Instance	Process	Arrival Time	Ready Queue	Running Queue	Execution Time	Initial Burst Time	Remaining Burst  Time
4-6ms	P1	0ms	P1, P4, P2	P3	0ms	3ms	3ms
	P2	1ms			0ms	2ms	2ms
	P3	2ms			2ms	2ms	0ms

At time = 6,

• Process P3 completes its execution
• Process P1 starts executing for TQ period as it is next in the b.

Time Instance	Process	Arrival Time	Ready Queue	Running Queue	Execution Time	Initial Burst Time	Remaining Burst  Time
6-8ms	P1	0ms	P4, P2	P1	2ms	3ms	1ms
	P2	1ms			0ms	2ms	2ms

At time = 8,

• Process P4 starts executing, it will not execute for Time Quantum period as it has burst time = 1
• Hence, it will execute for only 1ms. 

Time Instance	Process	Arrival Time	Ready Queue	Running Queue	Execution Time	Initial Burst Time	Remaining Burst  Time
8-9ms	P1	0ms	P2, P1	P4	0ms	3ms	1ms
	P2	1ms			0ms	2ms	2ms
	P4	4ms			1ms	1ms	0ms

At time = 9,

• Process P4 completes its execution
• Process P2 starts executing for TQ period as it is next in the ready queue

Time Instance	Process	Arrival Time	Ready Queue	Running Queue	Execution Time	Initial Burst Time	Remaining Burst  Time
9-11ms	P1	0ms	P1	P2	0ms	3ms	1ms
	P2	1ms			2ms	2ms	0ms

At time = 11,

• Process P2 completes its execution.
• Process P1 starts executing, it will execute for 1ms only

Time Instance	Process	Arrival Time	Ready Queue	Running Queue	Execution Time	Initial Burst Time	Remaining Burst  Time
11-12ms	P1	0ms		P1	1ms	1ms	0ms

At time = 12,

• Process P1 completes its execution.
• The overall execution of the processes will be as shown below:

Time Instance	Process	Arrival Time	Ready Queue	Running Queue	Execution Time	Initial Burst Time	Remaining Burst  Time
0-2ms	P1	0ms	P2, P3	P1	2ms	5ms	3ms
2-4ms	P1	0ms	P3, P1	P2	0ms	3ms	3ms
	P2	1ms			2ms	4ms	2ms
4-6ms	P1	0ms	P1, P4, P2	P3	0ms	3ms	3ms
	P2	1ms			0ms	2ms	2ms
	P3	2ms			2ms	2ms	0ms
6-8ms	P1	0ms	P4, P2	P1	2ms	3ms	1ms
	P2	1ms			0ms	2ms	2ms
8-9ms	P1	0ms	P2, P1	P4	0ms	3ms	1ms
	P2	1ms			0ms	2ms	2ms
	P4	4ms			1ms	1ms	0ms
9-11ms	P1	0ms	P1	P2	0ms	3ms	1ms
	P2	1ms			2ms	2ms	0ms
11-12ms	P1	0ms		P1	1ms	1ms	0ms

Gantt chart will be as following below: 

Gantt chart for Round Robin Scheduling Algorithm

How to compute below times in Round Robin using a program?

• Completion Time: Time at which process completes its execution.
• Turn Around Time: Time Difference between completion time and arrival time. Turn Around Time = Completion Time – Arrival Time
• Waiting Time(W.T): Time Difference between turn around time and burst time. 
  Waiting Time = Turn Around Time – Burst Time

Now, lets calculate average waiting time and turn around time:

Processes	AT	BT	CT	TAT	WT
P1	0	5	12	12-0 = 12	12-5 = 7
P2	1	4	11	11-1 = 10	10-4 = 6
P3	2	2	6	6-2 = 4	4-2 = 2
P4	4	1	9	9-4 = 5	5-1 = 4

Now, 

• Average Turn around time = (12 + 10 + 4 + 5)/4 = 31/4 = 7.7
• Average waiting time = (7 + 6 + 2 + 4)/4 = 19/4 = 4.7

Example 2: Consider the following table of arrival time and burst time for three processes P1, P2 and P3 and given Time Quantum = 2

Process	Burst Time	Arrival Time
P1	10 ms	0 ms
P2	5 ms	0 ms
P3	8 ms	0 ms

Similarly, Gantt chart for this example:

Gantt chart for example 2

Now, lets calculate average waiting time and turn around time:

Processes	AT	BT	CT	TAT	WT
P1	0	10	23	23-0 = 23	23-10 = 13
P2	0	5	15	15-0 = 15	15-5 = 10
P3	0	8	21	21-0 = 21	21-8 = 13

Total Turn Around Time = 59 ms
So, Average Turn Around Time = 59/3 = 19.667 ms

And, Total Waiting Time = 36 ms
So, Average Waiting Time = 36/3 = 12.00 ms 

Program for Round Robin Scheduling with arrival time as 0 for all processes

Steps to find waiting times of all processes

• Create an array rem_bt[] to keep track of remaining burst time of processes. This array is initially a copy of bt[] (burst times array)
• Create another array wt[] to store waiting times of processes. Initialize this array as 0.
• Initialize time : t = 0
• Keep traversing all the processes while they are not done. Do following for i’th process if it is not done yet.
  • If rem_bt[i] > quantum
    • t = t + quantum
    • rem_bt[i] -= quantum;
  • Else // Last cycle for this process
    • t = t + rem_bt[i];
    • wt[i] = t – bt[i]
    • rem_bt[i] = 0; // This process is over

Once we have waiting times, we can compute turn around time tat[i] of a process as sum of waiting and burst times, i.e., wt[i] + bt[i]

Below is implementation of above steps. 

C++

// C++ program for implementation of RR scheduling
#include<iostream>
using namespace std;

// Function to find the waiting time for all
// processes
void findWaitingTime(int processes[], int n,
            int bt[], int wt[], int quantum)
{
    // Make a copy of burst times bt[] to store remaining
    // burst times.
    int rem_bt[n];
    for (int i = 0 ; i < n ; i++)
        rem_bt[i] = bt[i];

    int t = 0; // Current time

    // Keep traversing processes in round robin manner
    // until all of them are not done.
    while (1)
    {
        bool done = true;

        // Traverse all processes one by one repeatedly
        for (int i = 0 ; i < n; i++)
        {
            // If burst time of a process is greater than 0
            // then only need to process further
            if (rem_bt[i] > 0)
            {
                done = false; // There is a pending process

                if (rem_bt[i] > quantum)
                {
                    // Increase the value of t i.e. shows
                    // how much time a process has been processed
                    t += quantum;

                    // Decrease the burst_time of current process
                    // by quantum
                    rem_bt[i] -= quantum;
                }

                // If burst time is smaller than or equal to
                // quantum. Last cycle for this process
                else
                {
                    // Increase the value of t i.e. shows
                    // how much time a process has been processed
                    t = t + rem_bt[i];

                    // Waiting time is current time minus time
                    // used by this process
                    wt[i] = t - bt[i];

                    // As the process gets fully executed
                    // make its remaining burst time = 0
                    rem_bt[i] = 0;
                }
            }
        }

        // If all processes are done
        if (done == true)
        break;
    }
}

// Function to calculate turn around time
void findTurnAroundTime(int processes[], int n,
                        int bt[], int wt[], int tat[])
{
    // calculating turnaround time by adding
    // bt[i] + wt[i]
    for (int i = 0; i < n ; i++)
        tat[i] = bt[i] + wt[i];
}

// Function to calculate average time
void findavgTime(int processes[], int n, int bt[],
                                    int quantum)
{
    int wt[n], tat[n], total_wt = 0, total_tat = 0;

    // Function to find waiting time of all processes
    findWaitingTime(processes, n, bt, wt, quantum);

    // Function to find turn around time for all processes
    findTurnAroundTime(processes, n, bt, wt, tat);

    // Display processes along with all details
    cout << "PN\t "<< " \tBT "
        << "  WT " << " \tTAT\n";

    // Calculate total waiting time and total turn
    // around time
    for (int i=0; i<n; i++)
    {
        total_wt = total_wt + wt[i];
        total_tat = total_tat + tat[i];
        cout << " " << i+1 << "\t\t" << bt[i] <<"\t "
            << wt[i] <<"\t\t " << tat[i] <<endl;
    }

    cout << "Average waiting time = "
        << (float)total_wt / (float)n;
    cout << "\nAverage turn around time = "
        << (float)total_tat / (float)n;
}

// Driver code
int main()
{
    // process id's
    int processes[] = { 1, 2, 3};
    int n = sizeof processes / sizeof processes[0];

    // Burst time of all processes
    int burst_time[] = {10, 5, 8};

    // Time quantum
    int quantum = 2;
    findavgTime(processes, n, burst_time, quantum);
    return 0;
}

Java

// Java program for implementation of RR scheduling

public class GFG
{
    // Method to find the waiting time for all
    // processes
    static void findWaitingTime(int processes[], int n,
                 int bt[], int wt[], int quantum)
    {
        // Make a copy of burst times bt[] to store remaining
        // burst times.
        int rem_bt[] = new int[n];
        for (int i = 0 ; i < n ; i++)
            rem_bt[i] =  bt[i];

        int t = 0; // Current time

        // Keep traversing processes in round robin manner
        // until all of them are not done.
        while(true)
        {
            boolean done = true;

            // Traverse all processes one by one repeatedly
            for (int i = 0 ; i < n; i++)
            {
                // If burst time of a process is greater than 0
                // then only need to process further
                if (rem_bt[i] > 0)
                {
                    done = false; // There is a pending process

                    if (rem_bt[i] > quantum)
                    {
                        // Increase the value of t i.e. shows
                        // how much time a process has been processed
                        t += quantum;

                        // Decrease the burst_time of current process
                        // by quantum
                        rem_bt[i] -= quantum;
                    }

                    // If burst time is smaller than or equal to
                    // quantum. Last cycle for this process
                    else
                    {
                        // Increase the value of t i.e. shows
                        // how much time a process has been processed
                        t = t + rem_bt[i];

                        // Waiting time is current time minus time
                        // used by this process
                        wt[i] = t - bt[i];

                        // As the process gets fully executed
                        // make its remaining burst time = 0
                        rem_bt[i] = 0;
                    }
                }
            }

            // If all processes are done
            if (done == true)
              break;
        }
    }

    // Method to calculate turn around time
    static void findTurnAroundTime(int processes[], int n,
                            int bt[], int wt[], int tat[])
    {
        // calculating turnaround time by adding
        // bt[i] + wt[i]
        for (int i = 0; i < n ; i++)
            tat[i] = bt[i] + wt[i];
    }

    // Method to calculate average time
    static void findavgTime(int processes[], int n, int bt[],
                                         int quantum)
    {
        int wt[] = new int[n], tat[] = new int[n];
        int total_wt = 0, total_tat = 0;

        // Function to find waiting time of all processes
        findWaitingTime(processes, n, bt, wt, quantum);

        // Function to find turn around time for all processes
        findTurnAroundTime(processes, n, bt, wt, tat);

        // Display processes along with all details
        System.out.println("PN " + " B " +
                      " WT " + " TAT");

        // Calculate total waiting time and total turn
        // around time
        for (int i=0; i<n; i++)
        {
            total_wt = total_wt + wt[i];
            total_tat = total_tat + tat[i];
            System.out.println(" " + (i+1) + "\t\t" + bt[i] +"\t " +
                              wt[i] +"\t\t " + tat[i]);
        }

        System.out.println("Average waiting time = " +
                          (float)total_wt / (float)n);
        System.out.println("Average turn around time = " +
                           (float)total_tat / (float)n);
    }

    // Driver Method
    public static void main(String[] args)
    {
        // process id's
        int processes[] = { 1, 2, 3};
        int n = processes.length;

        // Burst time of all processes
        int burst_time[] = {10, 5, 8};

        // Time quantum
        int quantum = 2;
        findavgTime(processes, n, burst_time, quantum);
    }
}

Python3

# Python3 program for implementation of
# RR scheduling

# Function to find the waiting time
# for all processes
def findWaitingTime(processes, n, bt,
                         wt, quantum):
    rem_bt = [0] * n

    # Copy the burst time into rt[]
    for i in range(n):
        rem_bt[i] = bt[i]
    t = 0 # Current time

    # Keep traversing processes in round
    # robin manner until all of them are
    # not done.
    while(1):
        done = True

        # Traverse all processes one by
        # one repeatedly
        for i in range(n):

            # If burst time of a process is greater
            # than 0 then only need to process further
            if (rem_bt[i] > 0) :
                done = False # There is a pending process

                if (rem_bt[i] > quantum) :

                    # Increase the value of t i.e. shows
                    # how much time a process has been processed
                    t += quantum

                    # Decrease the burst_time of current
                    # process by quantum
                    rem_bt[i] -= quantum

                # If burst time is smaller than or equal
                # to quantum. Last cycle for this process
                else:

                    # Increase the value of t i.e. shows
                    # how much time a process has been processed
                    t = t + rem_bt[i]

                    # Waiting time is current time minus
                    # time used by this process
                    wt[i] = t - bt[i]

                    # As the process gets fully executed
                    # make its remaining burst time = 0
                    rem_bt[i] = 0

        # If all processes are done
        if (done == True):
            break

# Function to calculate turn around time
def findTurnAroundTime(processes, n, bt, wt, tat):

    # Calculating turnaround time
    for i in range(n):
        tat[i] = bt[i] + wt[i]


# Function to calculate average waiting
# and turn-around times.
def findavgTime(processes, n, bt, quantum):
    wt = [0] * n
    tat = [0] * n

    # Function to find waiting time
    # of all processes
    findWaitingTime(processes, n, bt,
                         wt, quantum)

    # Function to find turn around time
    # for all processes
    findTurnAroundTime(processes, n, bt,
                                wt, tat)

    # Display processes along with all details
    print("Processes    Burst Time     Waiting",
                     "Time    Turn-Around Time")
    total_wt = 0
    total_tat = 0
    for i in range(n):

        total_wt = total_wt + wt[i]
        total_tat = total_tat + tat[i]
        print(" ", i + 1, "\t\t", bt[i],
              "\t\t", wt[i], "\t\t", tat[i])

    print("\nAverage waiting time = %.5f "%(total_wt /n) )
    print("Average turn around time = %.5f "% (total_tat / n))

# Driver code
if __name__ =="__main__":

    # Process id's
    proc = [1, 2, 3]
    n = 3

    # Burst time of all processes
    burst_time = [10, 5, 8]

    # Time quantum
    quantum = 2;
    findavgTime(proc, n, burst_time, quantum)

# This code is contributed by
# Shubham Singh(SHUBHAMSINGH10)

C#

// C# program for implementation of RR
// scheduling
using System;

public class GFG {

    // Method to find the waiting time
    // for all processes
    static void findWaitingTime(int []processes,
             int n, int []bt, int []wt, int quantum)
    {

        // Make a copy of burst times bt[] to
        // store remaining burst times.
        int []rem_bt = new int[n];

        for (int i = 0 ; i < n ; i++)
            rem_bt[i] = bt[i];

        int t = 0; // Current time

        // Keep traversing processes in round
        // robin manner until all of them are
        // not done.
        while(true)
        {
            bool done = true;

            // Traverse all processes one by
            // one repeatedly
            for (int i = 0 ; i < n; i++)
            {
                // If burst time of a process
                // is greater than 0 then only
                // need to process further
                if (rem_bt[i] > 0)
                {

                    // There is a pending process
                    done = false;

                    if (rem_bt[i] > quantum)
                    {
                        // Increase the value of t i.e.
                        // shows how much time a process
                        // has been processed
                        t += quantum;

                        // Decrease the burst_time of
                        // current process by quantum
                        rem_bt[i] -= quantum;
                    }

                    // If burst time is smaller than
                    // or equal to quantum. Last cycle
                    // for this process
                    else
                    {

                        // Increase the value of t i.e.
                        // shows how much time a process
                        // has been processed
                        t = t + rem_bt[i];

                        // Waiting time is current
                        // time minus time used by
                        // this process
                        wt[i] = t - bt[i];

                        // As the process gets fully
                        // executed make its remaining
                        // burst time = 0
                        rem_bt[i] = 0;
                    }
                }
            }

            // If all processes are done
            if (done == true)
            break;
        }
    }

    // Method to calculate turn around time
    static void findTurnAroundTime(int []processes,
               int n, int []bt, int []wt, int []tat)
    {
        // calculating turnaround time by adding
        // bt[i] + wt[i]
        for (int i = 0; i < n ; i++)
            tat[i] = bt[i] + wt[i];
    }

    // Method to calculate average time
    static void findavgTime(int []processes, int n,
                             int []bt, int quantum)
    {
        int []wt = new int[n];
        int []tat = new int[n];
        int total_wt = 0, total_tat = 0;

        // Function to find waiting time of
        // all processes
        findWaitingTime(processes, n, bt, wt, quantum);

        // Function to find turn around time
        // for all processes
        findTurnAroundTime(processes, n, bt, wt, tat);

        // Display processes along with
        // all details
        Console.WriteLine("Processes " + " Burst time " +
                    " Waiting time " + " Turn around time");

        // Calculate total waiting time and total turn
        // around time
        for (int i = 0; i < n; i++)
        {
            total_wt = total_wt + wt[i];
            total_tat = total_tat + tat[i];
            Console.WriteLine(" " + (i+1) + "\t\t" + bt[i]
                         + "\t " + wt[i] +"\t\t " + tat[i]);
        }

        Console.WriteLine("Average waiting time = " +
                        (float)total_wt / (float)n);
        Console.Write("Average turn around time = " +
                        (float)total_tat / (float)n);
    }

    // Driver Method
    public static void Main()
    {
        // process id's
        int []processes = { 1, 2, 3};
        int n = processes.Length;

        // Burst time of all processes
        int []burst_time = {10, 5, 8};

        // Time quantum
        int quantum = 2;
        findavgTime(processes, n, burst_time, quantum);
    }
}

// This code is contributed by nitin mittal.

Javascript

<script>
    // JavaScript program for implementation of RR scheduling

    // Function to find the waiting time for all
    // processes
    const findWaitingTime = (processes, n, bt, wt, quantum) => {
        // Make a copy of burst times bt[] to store remaining
        // burst times.
        let rem_bt = new Array(n).fill(0);
        for (let i = 0; i < n; i++)
            rem_bt[i] = bt[i];

        let t = 0; // Current time

        // Keep traversing processes in round robin manner
        // until all of them are not done.
        while (1) {
            let done = true;

            // Traverse all processes one by one repeatedly
            for (let i = 0; i < n; i++) {
                // If burst time of a process is greater than 0
                // then only need to process further
                if (rem_bt[i] > 0) {
                    done = false; // There is a pending process

                    if (rem_bt[i] > quantum) {
                        // Increase the value of t i.e. shows
                        // how much time a process has been processed
                        t += quantum;

                        // Decrease the burst_time of current process
                        // by quantum
                        rem_bt[i] -= quantum;
                    }

                    // If burst time is smaller than or equal to
                    // quantum. Last cycle for this process
                    else {
                        // Increase the value of t i.e. shows
                        // how much time a process has been processed
                        t = t + rem_bt[i];

                        // Waiting time is current time minus time
                        // used by this process
                        wt[i] = t - bt[i];

                        // As the process gets fully executed
                        // make its remaining burst time = 0
                        rem_bt[i] = 0;
                    }
                }
            }

            // If all processes are done
            if (done == true)
                break;
        }
    }

    // Function to calculate turn around time
    const findTurnAroundTime = (processes, n, bt, wt, tat) => {
        // calculating turnaround time by adding
        // bt[i] + wt[i]
        for (let i = 0; i < n; i++)
            tat[i] = bt[i] + wt[i];
    }

    // Function to calculate average time
    const findavgTime = (processes, n, bt, quantum) => {
        let wt = new Array(n).fill(0), tat = new Array(n).fill(0);
        let total_wt = 0, total_tat = 0;

        // Function to find waiting time of all processes
        findWaitingTime(processes, n, bt, wt, quantum);

        // Function to find turn around time for all processes
        findTurnAroundTime(processes, n, bt, wt, tat);

        // Display processes along with all details
        document.write(`Processes Burst time Waiting time Turn around time<br/>`);

        // Calculate total waiting time and total turn
        // around time
        for (let i = 0; i < n; i++) {
            total_wt = total_wt + wt[i];
            total_tat = total_tat + tat[i];

            document.write(`${i + 1} ${bt[i]} ${wt[i]} ${tat[i]}<br/>`);
        }

        document.write(`Average waiting time = ${total_wt / n}`);
        document.write(`<br/>Average turn around time = ${total_tat / n}`);
    }

    // Driver code
    // process id's
    processes = [1, 2, 3];
    let n = processes.length;

    // Burst time of all processes
    let burst_time = [10, 5, 8];

    // Time quantum
    let quantum = 2;
    findavgTime(processes, n, burst_time, quantum);

    // This code is contributed by rakeshsahni

</script>

Output

PN          BT   WT      TAT
 1        10     13         23
 2        5     10         15
 3        8     13         21
Average waiting time = 12
Average turn around time = 19.6667

Program for Round Robin Scheduling with arrival time as zero , different and same arrival times

C++

#include <iostream>
#include <climits>
using namespace std;

struct Process {
    int AT, BT, ST[20], WT, FT, TAT, pos;
};

int quant;

int main() {
    int n, i, j;

    // Taking Input
    cout << "Enter the no. of processes: ";
    cin >> n;
    Process p[n];

    cout << "Enter the quantum: " << endl;
    cin >> quant;

    cout << "Enter the process numbers: " << endl;
    for (i = 0; i < n; i++)
        cin >> p[i].pos;

    cout << "Enter the Arrival time of processes: " << endl;
    for (i = 0; i < n; i++)
        cin >> p[i].AT;

    cout << "Enter the Burst time of processes: " << endl;
    for (i = 0; i < n; i++)
        cin >> p[i].BT;

    // Declaring variables
    int c = n, s[n][20];
    float time = 0, mini = INT_MAX, b[n], a[n];

    // Initializing burst and arrival time arrays
    int index = -1;
    for (i = 0; i < n; i++) {
        b[i] = p[i].BT;
        a[i] = p[i].AT;
        for (j = 0; j < 20; j++) {
            s[i][j] = -1;
        }
    }

    int tot_wt, tot_tat;
    tot_wt = 0;
    tot_tat = 0;
    bool flag = false;

    while (c != 0) {
        mini = INT_MAX;
        flag = false;

        for (i = 0; i < n; i++) {
            float p = time + 0.1;
            if (a[i] <= p && mini > a[i] && b[i] > 0) {
                index = i;
                mini = a[i];
                flag = true;
            }
        }

        // if at =1 then loop gets out hence set flag to false
        if (!flag) {
            time++;
            continue;
        }

        // calculating start time
        j = 0;

        while (s[index][j] != -1) {
            j++;
        }

        if (s[index][j] == -1) {
            s[index][j] = time;
            p[index].ST[j] = time;
        }

        if (b[index] <= quant) {
            time += b[index];
            b[index] = 0;
        } else {
            time += quant;
            b[index] -= quant;
        }

        if (b[index] > 0) {
            a[index] = time + 0.1;
        }

        // calculating arrival, burst, final times
        if (b[index] == 0) {
            c--;
            p[index].FT = time;
            p[index].WT = p[index].FT - p[index].AT - p[index].BT;
            tot_wt += p[index].WT;
            p[index].TAT = p[index].BT + p[index].WT;
            tot_tat += p[index].TAT;
        }
    } // end of while loop

    // Printing output
    cout << "Process number ";
    cout << "Arrival time ";
    cout << "Burst time ";
    cout << "\tStart time";
    j = 0;
    while (j != 10) {
        j += 1;
        cout << " ";
    }
    cout << "\t\tFinal time";
    cout << "\tWait Time ";
    cout << "\tTurnAround Time" << endl;

    for (i = 0; i < n; i++) {
        cout << p[i].pos << "\t\t";
        cout << p[i].AT << "\t\t";
        cout << p[i].BT << "\t";
        j = 0;
        int v = 0;
        while (s[i][j] != -1) {
            cout << p[i].ST[j] << " ";
            j++;
            v += 3;
        }
        while (v != 40) {
            cout << " ";
            v += 1;
        }
        cout << p[i].FT << "\t\t";
        cout << p[i].WT << "\t\t";
        cout << p[i].TAT << endl;
    }

    // Calculating average wait time and turnaround time
    double avg_wt, avg_tat;
    avg_wt = tot_wt / static_cast<double>(n);
    avg_tat = tot_tat / static_cast<double>(n);

    // Printing average wait time and turnaround time
    cout << "The average wait time is: " << avg_wt << endl;
    cout << "The average TurnAround time is: " << avg_tat << endl;

    return 0;
}

C

#include<stdio.h>
#include<limits.h>
#include<stdbool.h>

struct P{
int AT,BT,ST[20],WT,FT,TAT,pos;
};

int quant;
int main(){
int n,i,j;
// Taking Input
printf("Enter the no. of processes :");
scanf("%d",&n);
struct P p[n];

printf("Enter the quantum  \n");
scanf("%d",&quant);

printf("Enter the process numbers \n");
for(i=0;i<n;i++)
scanf("%d",&(p[i].pos));

printf("Enter the Arrival time of processes \n");
for(i=0;i<n;i++)
scanf("%d",&(p[i].AT));

printf("Enter the Burst time of processes \n");
for(i=0;i<n;i++)
scanf("%d",&(p[i].BT));



// Declaring variables
int c=n,s[n][20];
float time=0,mini=INT_MAX,b[n],a[n];

// Initializing burst and arrival time arrays
int index=-1;
for(i=0;i<n;i++){
        b[i]=p[i].BT;
        a[i]=p[i].AT;
        for(j=0;j<20;j++){
        s[i][j]=-1;
        }
}

int tot_wt,tot_tat;
tot_wt=0;
tot_tat=0;
bool flag=false;

while(c!=0){

mini=INT_MAX;
flag=false;

for(i=0;i<n;i++){
        float p=time+0.1;
        if(a[i]<=p && mini>a[i] && b[i]>0){
        index=i;
        mini=a[i];
        flag=true;

        }
}
// if at =1 then loop gets out  hence set flag to false
if(!flag){
        time++;
        continue;
}

//calculating start time
j=0;

while(s[index][j]!=-1){
j++;
}

if(s[index][j]==-1){
s[index][j]=time;
p[index].ST[j]=time;
}

if(b[index]<=quant){
time+=b[index];
b[index]=0;
}
else{
time+=quant;
b[index]-=quant;
}

if(b[index]>0){
a[index]=time+0.1;
}

// calculating arrival,burst,final times
if(b[index]==0){
c--;
p[index].FT=time;
p[index].WT=p[index].FT-p[index].AT-p[index].BT;
tot_wt+=p[index].WT;
p[index].TAT=p[index].BT+p[index].WT;
tot_tat+=p[index].TAT;

}

} // end of while loop

// Printing output
printf("Process number ");
printf("Arrival time ");
printf("Burst time ");
printf("\tStart time");
j=0;
while(j!=10){
j+=1;
printf(" ");
}
printf("\t\tFinal time");
printf("\tWait Time ");
printf("\tTurnAround Time \n");


for(i=0;i<n;i++){
printf("%d \t\t",p[i].pos);
printf("%d \t\t",p[i].AT);
printf("%d \t",p[i].BT);
j=0;
int v=0;
while(s[i][j]!=-1){
printf("%d ",p[i].ST[j]);
j++;
v+=3;
}
while(v!=40){
printf(" ");
v+=1;
}
printf("%d \t\t",p[i].FT);
printf("%d \t\t",p[i].WT);
printf("%d \n",p[i].TAT);

}

//Calculating average wait time and turnaround time
double avg_wt,avg_tat;
avg_wt=tot_wt/(float)n;
avg_tat=tot_tat/(float)n;

//Printing average wait time and turnaround time
printf("The average wait time is : %lf\n",avg_wt);
printf("The average TurnAround time is : %lf\n",avg_tat);

return 0;
}

Output:

Enter the number of processes : 4

Enter the time quanta : 2

Enter the process numbers : 1 2 3 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

Program for Round Robin Scheduling with Different Arrival Times for all Processes

For detailed implementation of Preemptive Round Robin algorithm with different arrival times for all processes please refer: Program for Round Robin Scheduling with different arrival times.

Conclusion

In conclusion, Round Robin CPU scheduling is a fair and preemptive algorithm that allocates a fixed time quantum to each process, ensuring equal CPU access. It is simple to implement but can lead to higher context-switching overhead. While it promotes fairness and prevents starvation, it may result in longer waiting times and reduced throughput, depending on the time quantum. Effective program implementation allows for the calculation of key metrics like completion time, turnaround time, and waiting time, aiding in performance evaluation and optimization.