EXPERIMENT 2
First Come First Serve (FCFS)
First Come First Serve CPU Scheduling Algorithm shortly known as FCFS is the first algorithm of CPU Process Scheduling Algorithm. In First Come First Serve Algorithm what we do is to allow the process to execute in linear manner.
This means that whichever process enters process enters the ready queue first is executed first. This shows that First Come First Serve Algorithm follows First In First Out (FIFO) principle
Example:
/*
* FCFS Scheduling Program in C
*/
#include <stdio.h>
int main()
{
int pid[15];
int bt[15];
int n;
printf("Enter the number of processes: ");
scanf("%d",&n);
printf("Enter process id of all the processes: ");
for(int i=0;i<n;i++)
{
scanf("%d",&pid[i]);
}
printf("Enter burst time of all the processes: ");
for(int i=0;i<n;i++)
{
scanf("%d",&bt[i]);
}
int i, wt[n];
wt[0]=0;
//for calculating waiting time of each process
for(i=1; i<n; i++)
{
wt[i]= bt[i-1]+ wt[i-1];
}
printf("Process ID Burst Time Waiting Time TurnAround Time\n");
float twt=0.0;
float tat= 0.0;
for(i=0; i<n; i++)
{
printf("%d\t\t", pid[i]);
printf("%d\t\t", bt[i]);
printf("%d\t\t", wt[i]);
//calculating and printing turnaround time of each process
printf("%d\t\t", bt[i]+wt[i]);
printf("\n");
//for calculating total waiting time
twt += wt[i];
//for calculating total turnaround time
tat += (wt[i]+bt[i]);
}
float att,awt;
//for calculating average waiting time
awt = twt/n;
//for calculating average turnaround time
att = tat/n;
printf("Avg. waiting time= %f\n",awt);
printf("Avg. turnaround time= %f",att);
}
1. Initialize two array pid[] and bt[] of size 15.
2. Ask the user for number of processes n.
3. Ask the user for process id and burst time for all n processes and store them into pid[] and bt[] respectively.
4. Calculate waiting time of each process by the formula wt[i] = wt[i-1] + bt[i-1].
5. Print Process Id, Burst Time, waiting time and Turnaround time of each process in tabular manner.
6. Calculate and print turnaround time of each process = bt[i] + wt[i].
7. Add waiting time of all the processes and store it in the variable twt.
8. Add turnaround time of all the processes and store it in the variable tat.
9. Calculate average waiting time as awt = twt/n.
10. Calculate average turnaround time as att = tat/n;
11. Print average waiting time and average turnaround time.
12. Exit.
1. Initialize two array pid[] and bt[] of size 20.
2. Ask the user for number of processes n.
3. Ask the user for process id and burst time for all n processes and store them into pid[] and bt[] respectively.
4. Sort all the processes according to their burst time.
5. Assign waiting time = 0 to the smallest process.
6. Calculate waiting time of each process by using two loops and adding all the burst time of previously completed processes.
7. Print Process Id, Burst Time, waiting time and Turnaround time of each process in tabular manner.
8. Calculate and print turnaround time of each process = bt[i] + wt[i].
9. Add waiting time of all the processes and store it in the variable total.
10. Add turnaround time of all the processes and store it in the variable totalT.
11. Calculate average waiting time as avg_wt = total/n.
12. Calculate average turnaround time as avg_tat = totalT/n;
13. Print average waiting time and average turnaround time.
14. Exit.
EXPERIMENT 3
The Dining Philosopher Problem – The Dining Philosopher Problem states that K philosophers seated around a circular table with one chopstick between each pair of philosophers. There is one chopstick between each philosopher. A philosopher may eat if he can pick up the two chopsticks adjacent to him. One chopstick may be picked up by any one of its adjacent followers but not both.
Semaphore Solution to Dining Philosopher –
Each philosopher is represented by the following pseudocode:
process P[i]
while true do
{ THINK;
PICKUP(CHOPSTICK[i], CHOPSTICK[i+1 mod 5]);
EAT;
PUTDOWN(CHOPSTICK[i], CHOPSTICK[i+1 mod 5])
}There are three states of the philosopher: THINKING, HUNGRY, and EATING. Here there are two semaphores: Mutex and a semaphore array for the philosophers. Mutex is used such that no two philosophers may access the pickup or putdown at the same time. The array is used to control the behavior of each philosopher. But, semaphores can result in deadlock due to programming errors.
CODE:
