Round Robin Program in C

This C program executes based on a Round Robin algorithm that gives a constant time quantum to each process in the ready queue. The essence of operation is that each process can expect an equitable time of CPU in a rotated fashion, disallowing any one process from taking over the CPU to the exclusion of all others, thus ensuring starvation-free operation of the system.

Step-by-Step Execution Flow:

1. Initialization:
   All processes are placed in the ready queue, typically ordered by their arrival time.
2. Time Quantum Allocation:
   Each process is assigned a fixed time quantum (or time slice). If a process completes within its time quantum, it leaves the queue. If not, it is preempted and placed at the end of the queue to await its next turn.
3. Cyclic Processing:
   The CPU scheduler will move through the queue, serving each process for the time quantum. When finished, the process is removed, and scheduling is continued.
4. Handling Process Completion:
   When it comes to a process finish, it is simply removed from the queue, and the scheduler simply continues to cycle through the processes remaining in the queue.
5. Starvation-Free and Fairness:
   Because every process is guaranteed CPU access each cycle, the algorithm is inherently fair and starvation-free.
6. Performance Metrics:
   
   • Average Waiting Time: The average time a process waits in the ready queue before its execution is completed.
   • Average Turnaround Time: The average time from process arrival to completion.
   • Context Switching: Frequent switching can occur if the time quantum is small, impacting efficiency.

The Round Robin CPU Scheduling algorithm allocates a fixed amount of processing time to a job before it is forced to wait its turn again. Each process gets a chance to execute for one time unit (as defined here), depending on the time section al-zampa, and upon the expiration of its time quantum, it is sent back to the end of the queue. This is repeated until all processes finish executing.

Let’s assume:

• Processes: P1, P2, P3, P4
• CPU Burst Times:
  
  • P1 = 3 units
  • P2 = 5 units
  • P3 = 2 units
  • P4 = 4 units
• Time Quantum = 1 unit

Step 1: Understanding the Gantt Chart

In this step, the Gantt chart illustrates the order in which processes execute.

13-14 P2

To obtain the waiting time for each process, we need to know when it finished firing and how long it waited while other job arrivals were being executed. Thus, the waiting time can be calculated as:

Waiting time=Turnaround time−Burst time

As a reminder, Turnaround time is the total time from arrival to completion.

Now let’s look at the waiting times for each process:

• P1: Waiting time = (4-1) + (8-5) = (3) + (3) = 6 units
• P2: Waiting time = (1-0) + (5-2) + (9-6) + (11-10) + (12-11) + (13-12) = 1 + 3 + 3 + 1 + 1 + 1 = 10 units
• P3: Waiting time = (2-0) + (6-3) = 2 + 3 = 5 units
• P4: Waiting time = (3-0) + (7-4) + (10-8) + (12-11) = 3 + 3 + 2 + 1 = 9 units

Step 3: Calculating Average Waiting Time

The average waiting time is the sum of the individual waiting times divided by the number of processes: 

Average waiting time=6+10+5+94=304=7.5 units

If we assume the quantum time to be 2ms, that means that each process has 2ms maximum to execute. If the process is not done after 2ms, it simply goes to the back of the queue for their next turn.

Initial State:

• At time 0, Process A arrives and starts execution.
• The Ready Queue is initially empty but will start filling as processes arrive.

• Cycle 1: Process A executes first, followed by Process B, and then Process C.
• Cycle 2: Process A executes again, followed by Process B, which now finishes. Then Process C continues to run.
• Cycle 3: Process A finishes, and then Process C runs.
• Cycle 4: Process C finishes executing.

Algorithm

Let’s look at some terminology before entering the algorithm:

• Burst time: It refers to the time required for a task to complete its execution on the CPU without any interruption

It starts when the task gets CPU access till it finishes execution, ignoring any wait time.

• Arrival time: The specific time when a task enters the ready queue, becoming eligible for CPU scheduling.
• Process ID: A special identifier assigned to each task for managing and tracking purposes.
• Waiting time: The total time a process spends in the ready queue, waiting for its next CPU time slot.

Step-by-Step Algorithm of Round Robin Scheduling in C

Step 1: Input processes: Gathering process details, including burst time, arrival time and process ID.

Step 2: Sort processes: Arranging processes based on their arrival time.

Step 3: Allocation of time quantum: Each task is assigned a fixed time quantum for execution.

Step 4: Execute processes: All tasks are executed for a time quantum or until the task is completed and either removed from the queue (if finished) or moved to the back of the queue till its next turn.

Step 5: Repeat steps: Continue the cycle till all tasks are executed.

Example Code with Sequential Arrival Time

In a sequential arrival time, each process comes to the CPU one after the other, increasing the process arrival time within a unit interval(i.e., 1 or any other constant). Hence, in this case, all processes were sequentially arriving at the CPU and were scheduled using the Round Robin algorithm.

Here is an example of sa equential arrival time:

C Code

#include <stdio.h>

void main() {
    int i, processes, sum = 0, cnt = 0, y, q, wt = 0, tat = 0, at[10], bt[10], temp[10];
    float avg_waitt, avg_turnat;

    // Input the number of processes
    printf("Total number of processes in the system: ");
    scanf("%d", &processes);

    y = processes;  // Assign number of processes to y

    // Input arrival time and burst time for each process
    for(i = 0; i < processes; i++) {
        printf("\nEnter the Arrival and Burst time of Process[%d]\n", i + 1);
        printf("Arrival time: ");
        scanf("%d", &at[i]);
        printf("Burst time: ");
        scanf("%d", &bt[i]);
        temp[i] = bt[i];  // Initialize remaining burst time
    }

    // Input the time quantum
    printf("Enter the Time Quantum: ");
    scanf("%d", &q);

    // Display header for the process info
    printf("\nProcess No \tBurst Time \tTAT \t\tWaiting Time\n");

    // Scheduling loop
    for(sum = 0, i = 0; y != 0;) {
        if(temp[i] <= q && temp[i] > 0) {
            sum = sum + temp[i];
            temp[i] = 0;
            cnt = 1;
        } else if(temp[i] > 0) {
            temp[i] = temp[i] - q;
            sum = sum + q;
        }

        if(temp[i] == 0 && cnt == 1) {
            y--;  // Decrement remaining processes
            printf("\nProcess No[%d] \t%d \t\t%d \t\t%d", i + 1, bt[i], sum - at[i], sum - at[i] - bt[i]);
            wt = wt + sum - at[i] - bt[i];  // Calculate waiting time
            tat = tat + sum - at[i];  // Calculate turnaround time
            cnt = 0;
        }

        if(i == processes - 1) {
            i = 0;
        } else if(at[i + 1] <= sum) {
            i++;
        } else {
            i = 0;
        }
    }

    // Calculate average waiting time and turnaround time
    avg_waitt = wt * 1.0 / processes;
    avg_turnat = tat * 1.0 / processes;

    printf("\nAverage Turnaround Time: %f", avg_turnat);
    printf("\nAverage Waiting Time: %f", avg_waitt);
}

Explanation

This program implements the Round Robin scheduling algorithm. It receives the number of processes, their arrival and burst times as inputs. Then, once the waiting time, turnaround time, and averages for all processes are calculated, the CPU time is allocated to each process in the time slices of the fixed time quantum.

Output

//Input
Total number of processes in the system: 3

Enter the Arrival and Burst time of Process[1]
Arrival time: 0
Burst time: 5

Enter the Arrival and Burst time of Process[2]
Arrival time: 1
Burst time: 3

Enter the Arrival and Burst time of Process[3]
Arrival time: 2
Burst time: 4

Enter the Time Quantum: 3

//output

Process No    Burst Time    TAT         Waiting Time
Process No[1]    5        8           3
Process No[2]    3        6           3
Process No[3]    4        7           3

Average Turnaround Time: 7.000000
Average Waiting Time: 3.000000

• Time Complexity: O(n * m)‍
• Space Complexity: O(n)

Bottom Line 

Round Robin provides equitable CPU time access for every process, which make it particularly suitable for multitasking systems. Due to its cyclic execution and fixed time quantum, it is guaranteed that no process will be starved and the system will remain responsive. If you want to truly understand how RR works, implement the C program for round robin scheduling, coding it once, which clarifies everything better than theory.

CPU scheduling with zero arrival time is a situation in which all the processes arrive at 0. The scheduler does not discriminate between arrival times; all these processes are available to the CPU at the same point in time, thus making it focus only on the burst times (execution times) of the processes.

Algorithm

Step 1: Initialize the processes with the parameters timeQuantum, current_time, waiting_time, turnaround_time, completed_processes.

Step 2: While fewer than the total number of processes have been completed:

For any process:

If remaining burst > quantum:

Subtract quantum increment, current_time.

Else:

Increment current_time back with remaining burst, update waiting time and turnaround time, completed.

Step 3: Average waiting time and turnaround time calculated and printed.

C Code

#include <stdio.h>

#define MAX 10  // Maximum number of processes

// Structure to hold process details
struct Process {
    int id;         // Process ID
    int burstTime;  // Burst Time
    int remainingTime; // Remaining Time
};

// Function to implement Round Robin scheduling
void roundRobin(struct Process processes[], int n, int timeQuantum) {
    int time = 0;  // Tracks current time
    int completed = 0;
    int waitingTime = 0, turnaroundTime = 0;

    // Array to track the remaining time of each process
    while (completed < n) {
        for (int i = 0; i < n; i++) {
            // If process still has remaining time
            if (processes[i].remainingTime > 0) {
                if (processes[i].remainingTime > timeQuantum) {
                    processes[i].remainingTime -= timeQuantum;
                    time += timeQuantum;
                } else {
                    time += processes[i].remainingTime;
                    waitingTime += time - processes[i].burstTime;
                    turnaroundTime += time;
                    processes[i].remainingTime = 0;
                    completed++;
                }
            }
        }
    }

    printf("\nAverage Waiting Time = %.2f\n", (float)waitingTime / n);
    printf("Average Turnaround Time = %.2f\n", (float)turnaroundTime / n);
}

// Main function
int main() {
    struct Process processes[MAX];
    int n, timeQuantum;

    printf("Enter the number of processes: ");
    scanf("%d", &n);

    // Input processes burst times
    for (int i = 0; i < n; i++) {
        processes[i].id = i + 1;
        printf("Enter burst time for process %d: ", i + 1);
        scanf("%d", &processes[i].burstTime);
        processes[i].remainingTime = processes[i].burstTime;  // Initialize remaining time
    }

    printf("Enter time quantum: ");
    scanf("%d", &timeQuantum);

    // Run Round Robin Scheduling
    roundRobin(processes, n, timeQuantum);
    
    return 0;
}

Explanation

This above code uses a simulation of Round Robin scheduling by assigning a fixed quantum time for every process. It proceeds in cycles along the processes, executing each in cycles, updating burst times, and then calculating waiting and turnaround times for all processes until completion.

Output

Enter the number of processes: 3
Enter burst time for process 1: 10
Enter burst time for process 2: 5
Enter burst time for process 3: 8
Enter time quantum: 4

Average Waiting Time = 6.33
Average Turnaround Time = 13.33

• Time Complexity: O(n * m)
• Space Complexity: O(n)

Key Differences from the Previous Code

1. Arrival Times:

• Previous Code: Taken into consideration specific arrival times. This needs to be checked to make sure it is appropriate to execute the process once it has arrived to execute.
• Current Code: All processes can be assumed to arrive simultaneously (arrival time = 0) to simplify the logical processing of processes.

2. Idle CPU Handling:

• Previous Code: It will increment currentTime in the event that there are no processes that are ready to execute. This is appropriate since the CPU is expected to be idle and does not perform or execute work on any process.
• Current Code: It is unnecessary to check for idle time since the CPU is always anticipated to be busy, utilizing a time moot.

3. Turnaround Time Calculation:

• Previous Code: Here the Turnaround time is = Completion time - Arrival time.
• Current Code: The Turnaround time is = Completion time; since all the processes we use here have an arrival time = 0.

4. Code Complexity:

• Previous Code: More complex, checking for due to dynamic arrival times and idle processes.
• Current Code: More straightforward, as it is assumed that processes arrived simultaneously

In Round Robin (RR) scheduling, each process is cyclically assigned a fixed time quantum (or time slice). When there are different arrival times for the processes, the scheduler must consider the arrival time of each process before scheduling it. Round Robin with different arrival times works as follows:

Algorithm

Step 1: Initialize processes with timeQuantum, current_time, waiting_time, turnaround_time, completed_processes.

Step 2: While not all processes are completed:

Step 3: For each process:

• If remaining_burst > quantum, subtract quantum and increment current_time.
• Else, increment current_time by remaining burst, update waiting_time and turnaround_time, mark as completed.

Step 4: Calculate and print average waiting_time and turnaround_time.

Code

#include <stdio.h>

#define MAX 10  // Maximum number of processes

// Structure to hold process details
struct Process {
    int id;             // Process ID
    int arrivalTime;    // Arrival Time
    int burstTime;      // Burst Time
    int remainingTime;  // Remaining Time
    int waitingTime;    // Waiting Time
    int turnaroundTime; // Turnaround Time
};

// Function to implement Round Robin scheduling
void roundRobin(struct Process processes[], int n, int timeQuantum) {
    int currentTime = 0;  // Tracks current time
    int completed = 0;
    float totalWaitingTime = 0, totalTurnaroundTime = 0;

    while (completed < n) {
        for (int i = 0; i < n; i++) {
            if (processes[i].arrivalTime <= currentTime && processes[i].remainingTime > 0) {
                if (processes[i].remainingTime > timeQuantum) {
                    processes[i].remainingTime -= timeQuantum;
                    currentTime += timeQuantum;
                } else {
                    currentTime += processes[i].remainingTime;
                    processes[i].waitingTime = currentTime - processes[i].arrivalTime - processes[i].burstTime;
                    processes[i].turnaroundTime = currentTime - processes[i].arrivalTime;
                    totalWaitingTime += processes[i].waitingTime;
                    totalTurnaroundTime += processes[i].turnaroundTime;
                    processes[i].remainingTime = 0;
                    completed++;
                }
            }
        }
    }

    // Display results
    printf("\nProcess ID | Arrival Time | Burst Time | Waiting Time | Turnaround Time\n");
    for (int i = 0; i < n; i++) {
        printf("%9d | %12d | %10d | %12d | %15d\n", processes[i].id, processes[i].arrivalTime,
               processes[i].burstTime, processes[i].waitingTime, processes[i].turnaroundTime);
    }

    // Calculate averages
    printf("\nAverage Waiting Time = %.2f\n", totalWaitingTime / n);
    printf("Average Turnaround Time = %.2f\n", totalTurnaroundTime / n);
}

// Main function
int main() {
    struct Process processes[MAX];
    int n, timeQuantum;

    // Input number of processes
    printf("Enter the number of processes: ");
    scanf("%d", &n);

    // Input processes' arrival times and burst times
    for (int i = 0; i < n; i++) {
        processes[i].id = i + 1;
        printf("Enter arrival time and burst time for process %d: ", i + 1);
        scanf("%d %d", &processes[i].arrivalTime, &processes[i].burstTime);
        processes[i].remainingTime = processes[i].burstTime;  // Initialize remaining time
    }

    // Input time quantum
    printf("Enter time quantum: ");
    scanf("%d", &timeQuantum);

    // Run Round Robin Scheduling
    roundRobin(processes, n, timeQuantum);

    return 0;
}

Explanation

In the above example, the round robin scheduling with varying arrival times allocates CPU time in fixed time slices that cycle through the set of processes. Processes can start as per their arrival time, and if they don't complete in the quantum time frame, then they are suspended or preempted and get placed back in the queue. The process of CPU execution continues until all processes are executed.

Output

//Input
Enter the number of processes: 3
Enter arrival time and burst time for process 1: 0 10
Enter arrival time and burst time for process 2: 1 5
Enter arrival time and burst time for process 3: 2 8
Enter time quantum: 4

//Output
Process ID | Arrival Time | Burst Time | Waiting Time | Turnaround Time
         1 |           0 |         10 |           6 |              16
         2 |           1 |          5 |           4 |              9
         3 |           2 |          8 |           4 |              12

Average Waiting Time = 4.67
Average Turnaround Time = 12.33

• Time Complexity: O(n * m)
• Space Complexity: O(n)

Key Features

1. Handles Different Arrival Times:

Dynamically checks processes to see if they have arrived at each time step.

2. Idle CPU Handling:

Increments currentTime if no process i.e. no process is ready to simulate the CPU waiting for a new process to be ready to execute.

3. Fair Scheduling:

Distributes CPU time equally among all processes using round-robin scheduling.

4. Process Preemption:

Processes may be preempted (stopped) once their time quantum has expired and placed at the back of the queue.

5. Cyclic Execution:

Processes can execute in the queue continuously until termination.

6. Starvation-Free:

A starvation-free approach that guarantees the processes are provided CPU time.

7. Efficiency Considerations:

As the time quantum gets shorter, the number of context switches begins to increase the overhead to a point that can outweigh the beneficial usability.

Round Robi scheduling continues to have extensive use in multiple computing settings, owing to its fairness, simplicity, and cyclic execution as shown in the examples below:

1. Time-Sharing Systems

Round Robin is typically the scheduling algorithm used in time-sharing systems; this is when multiple users/processes are sharing CPU resources. By giving processes a time quantum, it ensures that there are quick context switches and fairness, allowing all users to experience responsive computing.

2. Interactive Systems

In interactive systems, such as graphical user interfaces, word processors, or terminal sessions, Round Robin scheduling keeps the user interface responsive. Each process in the ready queue gets a regular opportunity to use the CPU, preventing any single task from freezing the system.

3. Client-Server Architectures

Servers adopting a Round Robin would be those handling multiple client requests (Web servers and application servers) to ensure that processes can be serviced fairly. The advantage of the Round Robin algorithm is the avoidance of client starvation and equality of resource sharing.

4. Network Schedulers

Routers, switches, and other networking equipment commonly implement Round Robin in their network schedulers to coordinate data packet transmission. The network scheduler will cycle through each packet or flow and grant the fair use of the network shared bandwidth, effectively stopping a single connection from monopolizing the network.

5. Process Schedulers in Operating Systems

Operating systems also incorporate Round Robin into their process schedulers when managing processes from the ready queue. In a multitasking environment, this is a suitable and convenient way to allow processes to share time on the CPU, as each process is always guaranteed access to the CPU in a given or defined cycle.

6. Real-Time Systems (with Caution)

Round Robin is not the most practical scheduling algorithm choice for all real-time systems due to the fact that it does not allow for process priorities. However, in soft real-time systems, Round Robin can be used since fairness is valued more than the time predictability requirements. For hard real-time tasks, it is preferred that specialized schedulers be used.

7. Time-Sharing and Multi-User Environments

Educational institutions, research labs, and shared computing clusters frequently run Round Robin style scheduling, as users need the ability to run programs concurrently on the same CPU without any one program entirely monopolizing the CPU.

Relevant Terms Explained:

• Client Server Architecture: Systems where a server handles requests from multiple clients, benefiting from fair scheduling.
• Context Switching: The procedure of saving and restoring process states, which is frequent in Round Robin scheduling.
• Interactive System: Systems requiring immediate feedback to user actions, maintained by fair CPU allocation.
• Network Schedulers: Components in networking devices that manage transmission order for data packets.
• Process Schedulers: OS components that decide which process in the ready queue gets CPU time next.
• Ready Queue: The list of processes waiting to be scheduled for execution.
• Real-Time Systems: Systems with strict timing requirements; Round Robin may be used in soft real-time cases.
• Time Sharing System / Time-Sharing Systems: Environments where multiple users or tasks share computing resources via rapid context switching.

Round Robin scheduling is a widely used CPU scheduling algorithm, especially in time-sharing and multitasking systems. Understanding its advantages and limitations is important for anyone studying operating systems or preparing to implement this algorithm in C.

Advantages

1. Fairness and Starvation-Free:
   Round Robin is a starvation-free algorithm. Each process is guaranteed a fair opportunity to access and use the CPU such that a single process cannot simply be ignored or indefinitely wait.
2. Cyclic and Predictable Execution:
   Round Robin is characterized by its cyclical nature, which ensures that each process is executed in rotating order. Therefore, it is easy to describe, understand and implement this expected scheduling. 
3. Improved Responsiveness:
   Fixing a time quantum (or time slice) for each process allows the system to respond quickly to interacting processes. This obviously fits well with time-sharing environments and is important for the user experience. 
4. Simple Implementation:
   The algorithm is very simple, especially when coded using basic data structures such as simple queues. 
5. Context Switching Enables Multitasking:
   The system switches contexts often, allowing processes to run in parallel so that progress is being made on multiple processes in tandem. Thus, the system appears multitasked / responsive. 

Disadvantages

1. Context Switching Overhead:
   If the quantum is too small, much of the CPU's time in context switching rather than running the process which contributes to the efficiency of the system. 
2. Time Quantum Selection is Critical:
   Choosing the right time quantum is challenging.
   
   • A very large time quantum makes Round Robin behave like FCFS (First Come First Serve), reducing its benefits.
   • A very small time quantum increases context switching, hurting performance.
3. Longer Turnaround Time for Some Processes:
   Processes that may get a long burst may experience long waits before completing, as they are given their time, get preempted, and then cycle through the queue again for execution. 
4. Not Suitable for Priority or Real-Time Systems:
   Since processes are treated equally, Round Robin is not recommended within a system that has microprocesses / systems that have certain priorities or deadlines for some tasks. ‍
5. No Built-in Priority Handling:The algorithm does not consider process importance, which may not be suitable when some tasks are more critical than others.

1. Clearly Define Process Structure
   Design a struct to hold each process’s essential attributes: process ID, arrival time, burst time, remaining time, waiting time, and turnaround time. This makes your code organized and helps in tracking each process’s state throughout the scheduling.
2. Validate User Input Thoroughly
   Always check for valid input values such as positive burst times, non-negative arrival times, and a sensible time quantum (not zero or negative). Input validation prevents logical errors and unexpected behavior during execution.
3. Use a Queue Data Structure for Scheduling
   Implement the ready queue using an array or linked list to efficiently cycle through processes. A proper queue ensures that preempted processes are placed at the end, maintaining the cyclic nature of Round Robin scheduling.
4. Handle Context Switching and Time Advancement Carefully
   Accurately update the current time after each process’s time slice or completion. Make sure context switching is reflected in the simulation, and the scheduler advances time correctly, especially when new processes arrive or the CPU becomes idle.
5. Track and Calculate Performance Metrics
   Maintain variables to track waiting time and turnaround time for each process. After scheduling, compute and display average waiting time and average turnaround time, as these metrics are crucial for evaluating scheduling efficiency.
6. Test with Diverse Scenarios
   Test your implementation with a variety of input cases: all processes arriving at time zero, staggered arrival times, varying burst times, and different time quantum values. This ensures your program handles edge cases and behaves as expected in real-world scenarios.

These best practices will help you write robust, efficient, and easy-to-understand Round Robin scheduling programs in C, making your code ready for academic assignments, interviews, or real-world applications.

Round Robin stands out as one of the fairest and responsive CPU scheduling algorithms, especially for time-sharing and multitasking systems. It cycles through each process's sequential order with a time slice for the process, eliminating monopolization of CPU resources and allowing a smoother, efficient process switch time.

Why it matters:
Recognizing the rationale of round robin scheduling algorithms in C helps students to understand how actual operating systems control simultaneous multiple processes in a timely manner.

If you want to master this concept, don’t just read; try building a round robin program in C. Once you simulate time quanta, waiting time, and turnaround time in code, the core idea becomes crystal clear.

1. What is Round Robin scheduling in operating systems?

Round Robin(RR) is a preemptive CPU scheduling algorithm that assigns a fixed time quantum to each process. After the quantum expires, the process is preempted and placed at the back of the queue, allowing other methods to work on a particular CPU cycle.

2. How does Round Robin program in C work?

Round Robin creates a circular queue at the CPU that contains all processes. Each process has a time quantum that acts like an interval timer; then, the process is sent to the first unfinished process in the queue, ensuring that all processes get a fair share of the CPU time.

3. What are the advantages of Round Robin scheduling?

Round Robin is a scheduling algorithm emphasising fairness by making every process wait an equal time quantum. Starvation of processes is avoided, as the algorithm is also fair. Round Robin is also a widely accepted way of sharing time, in which all processes are treated equally.

4. What are the limitations of Round Robin scheduling?

The inefficiency of Round Robin scheduling occurs in those processes characterised by high-caliber limits. When a long-running process is transacted with other running processes, an inordinate number of context switches are made that incur overhead. With a small time quantum, there would be excessive switching, causing performance to plummet.

5. Is Round Robin scheduling suitable for real-time systems?

Round Robin cannot be given the right credit to offer a service to real-time systems, since it does not treat the procedures according to their deadline. Real-time systems use scheduling wherein RMS can be treated with great robustness, as this scheduling relates to timing constraints and the urgency of the tasks.

6. What is the Round Robin process scheduling in C?

Round Robin process scheduling in C is the algorithm implementation required to manage the processes in a queue and assign a fixed time slice to each. Once a process's time slice runs out, it is placed at the end of the queue.

7. What is a typical example of a Round Robin scheduling problem?

A common example involves a set of processes, each with specified arrival and burst times, scheduled using the Round Robin CPU scheduling policy. The goal is to determine the order of execution, average waiting time, and average turnaround time using a given time quantum.

8. How do you calculate average waiting time and average turn around time in Round Robin scheduling?

• Average waiting time is the total waiting time of all processes divided by the total number of processes.
• Average turn around time is the total time from a process’s arrival to its completion, averaged across all processes.
  In Round Robin scheduling, you simulate the execution in cycles, updating each process’s remaining burst time and tracking when each process finishes.

9. Can you provide a sample problem with a solution?

Example:
Suppose you have three processes:

• P1 (Burst Time = 5)
• P2 (Burst Time = 3)
• P3 (Burst Time = 4)
  With all processes arriving at time 0 and a time quantum of 2 units.

Solution Steps:

1. Run each process there 2 units in cyclic order.
2. Keep track of the remaining burst time of the last cycle. 
3. Continue to run all the processes until complete.
4. Calculate each process’s waiting time and turn-around time.
5. Compute the averages.

10. Why is the time quantum important in Round Robin examples?

The time quantum determines how long each process can run before being preempted. A small time quantum increases context switching but improves responsiveness, while a large time quantum reduces context switching but may delay shorter tasks.

11. What are some tips for solving Round Robin scheduling problems in exams or interviews?

• Write out the Gantt chart or execution order.
• Keep track of each process’s remaining burst time.
• Update waiting and turn-around times after each cycle.
• Double-check calculations for average waiting time and average turnaround time.
• Clearly state the time quantum used in your solution.