4d.c

// Round Robin 

#include <stdio.h> 
#define MAX 20

int rq[20], front = 0, rear = -1; 
struct process
{
    int pid, bt, btcopy, wt, tat;
} p[20], s;

void enqueue(int pid)
{
    if (rear > MAX - 1) 
        return;
    else
    {
        rear = rear + 1; rq[rear] = pid;
    }
}

int dequeue()
{
    int ele, i;
    if (rear == -1) 
        return -1;
    else
    {
        ele = rq[0];
        for (i = 0; i <= rear; i++) 
            rq[i] = rq[i + 1];
        rear--; return ele;
    }
}

int main()
{
    int n, i, j, sum = 0, ts, id, ct = 0; 
    printf("\nEnter the no. of processes : "); 
    scanf("%d", &n);
    printf("\nEnter the Time Slice : "); 
    scanf("%d", &ts);
    for (i = 0; i < n; i++)
    {
        p[i].pid = i;
        printf("\nEnter the burst time for Process %d : ", i); 
        scanf("%d", &p[i].bt);
        p[i].btcopy = p[i].bt;
    }
    for (i = 0; i < n; i++)
    {
        enqueue(i);
    }
    id = dequeue(); 
    printf("\nExecution order: "); 
    printf(" P%d->", id);
    while (id != -1)
    {
        if (p[id].bt > ts)
        {
            ct = ct + ts; p[id].tat = ct;
            p[id].bt = p[id].bt - ts;
            if (p[id].bt != 0)
                enqueue(p[id].pid);
        }
        else
        {
            ct = ct + p[id].bt; p[id].tat = ct;
            p[id].bt = 0;
        }
        id = dequeue(); if (id != -1)
        printf(" P%d->", id);
    }

    for (i = 0; i < n; i++)
        p[i].wt = p[i].tat - p[i].btcopy;
    printf("\n\n\n\tPID\t\tBurst Time\t\t Turnaround Time\t Waiting Time\n"); 
    for (i = 0; i < n; i++)
        printf("\n\t%d\t\t\t%d\t\t\t%d\t\t\t%d", p[i].pid, p[i].btcopy, p[i].tat, p[i].wt); 
    printf("\n");
    return 0;
}