SJF CPU SCHEDULING ALGORITHM

For SJF scheduling algorithm, read the number of processes/jobs in the system, their CPU burst times. Arrange all the jobs in order with respect to their burst times. There may be two jobs in queue with the same execution time, and then FCFS approach is to be performed. Each process will be executed according to the length of its burst time. Then calculate the waiting time and turnaround time of each of the processes accordingly


PROGRAM:-
#include<stdio.h>
#include<conio.h>
main()
{
int p[20], bt[20], wt[20], tat[20], i, k, n, temp;
float wtavg, tatavg;
clrscr();
printf("\nEnter the number of processes -- ");
scanf("%d", &n);
for(i=0;i<n;i++)
{
p[i]=i;
printf("Enter Burst Time for Process %d -- ", i);
scanf("%d", &bt[i]);
}
for(i=0;i<n;i++)
for(k=i+1;k<n;k++)
if(bt[i]>bt[k])
{
temp=bt[i];
bt[i]=bt[k];
bt[k]=temp;
temp=p[i];
p[i]=p[k];
p[k]=temp;
}
wt[0] = wtavg = 0;
tat[0] = tatavg = bt[0];
for(i=1;i<n;i++)
{
wt[i] = wt[i-1] +bt[i-1];
tat[i] = tat[i-1] +bt[i];
wtavg = wtavg + wt[i];
tatavg = tatavg + tat[i];
}
printf("\n\t PROCESS \tBURST TIME \t WAITING TIME\t TURNAROUND TIME\n");
for(i=0;i<n;i++)
printf("\n\t P%d \t\t %d \t\t %d \t\t %d", p[i], bt[i], wt[i], tat[i]);
printf("\nAverage Waiting Time -- %f", wtavg/n);
printf("\nAverage Turnaround Time -- %f", tatavg/n);
getch();

}


OUTPUT:-

FCFS CPU SCHEDULING ALGORITHM

For FCFS scheduling algorithm, read the number of processes/jobs in the system, their CPU burst times. The scheduling is performed on the basis of arrival time of the processes irrespective of their other parameters. Each process will be executed according to its arrival time. Calculate the waiting time and turnaround time of each of the processes accordingly




Program:-
#include<stdio.h>
#include<conio.h>
main()
{
int bt[20], wt[20], tat[20], i, n;
float wtavg, tatavg;
clrscr();
printf("\nEnter the number of processes -- ");
scanf("%d", &n);
for(i=0;i<n;i++)
{
printf("\nEnter Burst Time for Process %d -- ", i);
scanf("%d", &bt[i]);
}
wt[0] = wtavg = 0;
tat[0] = tatavg = bt[0];
for(i=1;i<n;i++)
{
wt[i] = wt[i-1] +bt[i-1];
tat[i] = tat[i-1] +bt[i];
wtavg = wtavg + wt[i];
tatavg = tatavg + tat[i];
}
printf("\t PROCESS \tBURST TIME \t WAITING TIME\t TURNAROUND TIME\n");
for(i=0;i<n;i++)
printf("\n\t P%d \t\t %d \t\t %d \t\t %d", i, bt[i], wt[i], tat[i]);
printf("\nAverage Waiting Time -- %f", wtavg/n);
printf("\nAverage Turnaround Time -- %f", tatavg/n);
getch();
}

Output:-

FCFS DISK SCHEDULING ALGORITHM

FCFS DISK SCHEDULING ALGORITHM

      The simplest form of disk scheduling is the First Come First Serve (FCFS) Algorithm. This algorithm is intrinsically fair, but it generally does not provide the fastest service queue data structure, where the data element which is added to the queue first, it is the one who issues the first queue. This is used in batch system. It is easy to understand and implement programmatic, using a queue data structure where a new process enters through the tail of queue and the scheduler selects process from the head of queue.

Program:

#include<stdio.h>

#include<conio.h>

int main()

{

int t[20],n,i,j,tohm[20],tot=0;

clrscr();

printf("Enter the head positon:");

scanf("%d",&t[0]);

printf("Enter the no.of tracks:");

scanf("%d",&n);

printf("Enter the tracks to be traversed:");

for(i=1;i<=n;i++)

scanf("%d",&t[i]);

for(i=0;i<=n;i++)

{

tohm[i]=t[i+1]-t[i];

if(tohm[i]<0)

tohm[i]=tohm[i]*(-1);

}

for(i=0;i<n;i++)

tot+=tohm[i];

printf("Tracks traversed\tDifference between tracks\n");

for(i=0;i<n;i++)

printf("\t%d\t\t\t%d\n",t[i],tohm[i]);

printf("\t%d\t\t\t0\n",t[i],0);

printf("\ total header movements:%d",tot);

getch();

return 0;

}

Output: