Round Robin Scheduling Algorithm (with arrival time)

C program for solving round-robin (with arrival time)

The round-robin (RR) the scheduling algorithm is designed especially for time-sharing systems. It is similar to FCFS scheduling, but pre-preemption is added to switch between processes. A small unit of time, called a time quantum or time slice, is defined. A time quantum is generally from 10 to 100 milliseconds. The ready queue is treated as a circular queue.

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It is one of the oldest, simplest, and fairest and most widely used scheduling algorithms, designed especially for time-sharing systems. A small unit of time, called time-slice or quantum, is defined. All runnable processes are kept in a circular queue. The CPU scheduler goes around this queue, allocating the CPU to each process for a time interval of one quantum. New processes are added to the tail of the queue.

CPU : Central Processing Unit

Program: 

#include<stdio.h> void main() {  int k, j, q, i, n, ts, temp;  int aw;  float awt;  int bt[10], wt[10], te[10], rt[10], at[10];  j = 0;  clrscr();  printf("enter number of process :\t");  scanf("%d", & n);  printf("\n enter brust time and arriavl time\n");  for (i = 0; i < n; i++) {    printf("P%d  \nbrust time ", i + 1);    scanf("%d", & bt[i]);    printf("ariavl time   :  ");    scanf("%d", & at[i]);    te[i] = 0;    wt[i] = 0;  }  for (i = 0; i < n; i++) {    for (j = i + 1; j < n; j++) {      if (at[i] > at[j]) {        temp = at[i]; //sorting according to arrival time        at[i] = at[j];        at[j] = temp;        temp = bt[i];        bt[i] = bt[j];        bt[j] = temp;      }    }  }  printf("\n enter time slice\t");  scanf("%d", & ts);  q = 0;  clrscr();  printf("\nprocess      :");  for (i = 0; i < n; i++) {    printf("  %d", i + 1);  }  printf("\nBrust time   :");  for (i = 0; i < n; i++) {    printf("  %d", bt[i]);    rt[i] = bt[i];  }  printf("\nArrival time :");  for (i = 0; i < n; i++) {    printf("  %d", at[i]);  }  printf("\n Gaint chart \n");  j = 0;  while (j <= n) {    j++;    for (i = 0; i < n; i++) {      if (rt[i] == 0) continue;      if (rt[i] > ts) {        printf("\n %d\t P%d", q, i + 1);        q = q + ts;        rt[i] = rt[i] - ts;        te[i] = te[i] + 1;      } else {        printf("\n %d\t P%d", q, i + 1);        wt[i] = q - te[i] * ts;        q = q + rt[i];        rt[i] = rt[i] - rt[i];      }    }  } //end of while      awt = 0;  printf("\n Process   Waitnig time");  for (i = 0; i < n; i++) {    wt[i] = wt[i] - at[i];    printf("\n P%d      :   %d", i + 1, wt[i]);    awt = awt + wt[i];  }  aw = awt;  printf("\ntotal waiting time %d", aw);  printf("\n Avg wainting time %f ", awt / n);  getch(); }

output:

Burst Time is actually time that is required to complete the execution of a particular task or process.