Os lab file c programs

OS Programs in C language.

1. Program 1

Write a C program to implement First-Come-First-Serve Algorithm.

#include<stdio.h>
#include<conio.h>
void main()
{
clrscr();
int pr,i,t=0,avg=0;
printf("Enter The Number Of Process\n");
scanf("%d",&pr);
char p[10];
int brst[10],Wt[10];
brst[0]=0;Wt[0]=0;
for(i=0;i<pr;i++)
{
printf("Enter The Name Of The Process\n");
scanf("%s",&p[i]);
printf("Enter The Burst Time Of The Process\n");
scanf("%d",&brst[i]);
}
t=Wt[0];
for(i=1;i<pr;i++)
{
Wt[i]=Wt[i-1]+brst[i-1];
t=t+Wt[i];
}
printf("\nProcess\tBurst Time\tWaiting Time\n");
for(i=0;i<pr;i++)
{
printf("p%d\t%d\t\t%d\t\n",i+1,brst[i],Wt[i]);
}
avg=t/pr;
printf("Total Waiting Time Is=%d\n",t);
printf("Average Waiting Time Is=%d\n",avg);
getch();
}

3. Program 2

Write a C program to implement non pre-emptive SJF scheduling algorithm.

#include<stdio.h>
#include<conio.h>
void main()
{
clrscr();
int n,i,j,temp,temp1,temp2,pr[10],bt[10],at[10],wt[10],tat[10];
float atat,awt,totaltat=0,totalwt=0;
for(i=0;i<10;i++)
{
bt[i]=0;
wt[i]=0;
}
printf("enter the number of process");
scanf("%d",&n);
for(i=0;i<n;i++)
{
pr[i]=i;
printf("\nenter the burst time of process p%d\t",i);
scanf("%d",&bt[i]);
printf("\nenter the arrival time of process p%d\t",i);
scanf("%d",&at[i]);
}
for(i=0;i<n;i++)
{
for(j=0;j<n;j++)
{
if(at[j]>at[i]&&bt[j]<at[i])
{
temp=bt[i];
bt[i]=bt[j];
bt[j]=temp;
temp1=pr[i];
pr[i]=pr[j];
pr[j]=temp1;
temp2=at[i];
at[i]=at[j];
at[j]=temp2;
}
}
}
wt[0]=0;
for(i=0;i<n;i++)

4. {
wt[i+1]=wt[i]+bt[i]-at[i+1];;
tat[i]=wt[i]+bt[i];
}
for(i=0;i<n;i++)
{
totalwt=totalwt+wt[i];
totaltat=totaltat+tat[i];
}
awt=totalwt/n;
atat=totaltat/n;
printf("\n\t process \tburt time\t arival time\twaiting time\n");
for(i=0;i<n;i++)
{
printf("\t p%d\t\t%d\t\t%d\t\t%d\n",pr[i],bt[i],at[i],wt[i]);
}
printf("the average waitingtimeis %f\n",awt);
printf("the average turn around time is %f\n",atat);
getch();
}

6. Program 3

Write a C program to implement non pre-emptive SJF scheduling algorithm.

#include<stdio.h>
#include<conio.h>
#include<string.h>
void main()
{
int i,j,k,n,Bt[10],wt[10],B[10],A[10],Tt=0;
char s[20],start[20];
int max=0,min,Time=0,z[50];
float Twt=0.0,Awt;
int w=0,flag=0,t=0;
clrscr();
printf("\n Enter no. of processes ::");
scanf("%d",&n);
for(i=1;i<=n;i++)
{
printf("\n Enter the Burst time for process P%d::",i);
scanf("%d",&Bt[i]);
printf("\n Enter the Arrival time for process P%d::",i);
scanf("%d",&A[i]);
B[i]=Bt[i];
if(B[i]>max)
max=B[i];
if(A[i]>Time)
Time=A[i];
wt[i]=0;
s[i]='T';
start[i]='F';
Tt+=B[i];
}
i=1;k=0;
z[k]=0;
k++;
while(t<Time)
{
if(A[i]<=t && B[i]!=0)
{
if(flag==0)
wt[i]=wt[i]+w;
B[i]=B[i]-1;
if(B[i]==0)
s[i]='F';
start[i]='T';
t++;
w=w+1;
if(s[i]!='F')

7. {
j=1;
flag=1;
while(j<=n&&flag!=0)
{
if(s[j]!='F'&&B[i]>B[j]&&A[i]<=t&&i!=j)
{
flag=0;
z[k]=w;
wt[i]=wt[i]-w;
i=j;
k++;
}
else
flag=1;
j++;
}
}
else
{
i++;
j=1;
while(A[j]<=t && j<=n)
{
if(B[i]>B[j] && s[j]!='F')
{
flag=0;
i=j;
}
j++;
}
}
}
else
{
if(flag==0)
i++;
}
}
while(w<Tt)
{
min=max+1;
i=1;
while(i<=n)
{
if(min>B[i]&&s[i]=='T')
{
min=B[i];
j=i;
}

8. i++;
}
i=j;
if(w==Time &&start[i]=='T')
{
w+=B[i];
z[k]=w;
k++;
s[i]='F';
}
else
{
wt[i]+=w;
w+=B[i];
z[k]=w;
k++;
s[i]='F';
}
}
printf("\n..............................................\n");
printf("\nPno\tBt\tAt\tWt");
printf("\n..............................................\n");
for(i=1;i<=n;i++)
{
wt[i]=wt[i]-A[i];
printf("\nP%d\t%d\t%d\t%d",i,Bt[i],A[i],wt[i]);
}
printf("\n..............................................\n");
printf("\n\n Gannt Chart ::\n");
for(i=0;i<k;i++)
printf("%4d",z[i]);
for(i=1;i<=n;i++)
Twt+=wt[i];
printf("\n\n Total waiting Time ::%f",Twt);
Awt=Twt/n;
printf("\n\n Average waiting Time ::%f",Awt);
getch();
}

10. Program 4

Write a C program to implement priority scheduling algorithm.

#include<stdio.h>
#include<conio.h>
void main()
{
int i,j,n,time[10],bursttime[10],wt[10],pt[10],temp2,total=0,p[10],temp;
float avgwt,avgtat;
int tat[10],totaltat=0;
clrscr();
printf("\nenter the no of process:");
scanf("\t%d",&n);
for(i=0;i<n;i++)
{
printf("\nenter the time of process P%d\t",i);
scanf("\n\t%d",&time[i]);
printf("\nenter the priority of process p%d\t",i);
scanf("\n\t%d",&pt[i]);
}
for(i=0;i<n;i++)
{
p[i]=i;
for(j=0;j<n;j++)
{
if(pt[i]<pt[j])
{
temp=pt[i];
pt[i]=pt[j];
pt[j]=temp;
temp=time[i];
time[i]=time[j];
time[j]=temp;
temp2=p[i];
p[i]=p[j];
p[j]=temp2;
}
}
}
wt[0]=0;
for(i=1;i<=n;i++)
{
wt[i]=wt[i-1]+time[i-1];
printf("\nthe wating time of process%d",p[i-1]);
printf("\t%d",wt[i-1]);
}
for(i=0;i<n;i++)
{

11. tat[i]=wt[i]+time[i];
}
printf("\nps\tct\tpt\twt\ttat");
for(i=0;i<n;i++)
{
printf("\np%d\t%2d\t%2d\t%2d\t%2d",p[i],time[i],pt[i],wt[i],tat[i]);
}
for(i=0;i<n;i++)
{
total=total+wt[i];
totaltat=totaltat+tat[i];
}
avgwt=float(total)/n;
avgtat=float(totaltat)/n;
printf("\navg waiting time is:\t%f",avgwt);
printf("\nAverage turn around time is :%f",avgtat);
getch();
}

13. Program 5

Write a C program to implement round robin.

#include<stdio.h>
#include<conio.h>
void main()
{
int st[10],bt[10],wt[10],tat[10],n,tq;
int i,count=0,swt=0,stat=0,temp,sq=0;
float awt=0.0,atat=0.0;
clrscr();
printf("Enter number of processes:");
scanf("%d",&n);
printf("Enter burst time for sequences:");
for(i=0;i<n;i++)
{
scanf("%d",&bt[i]);
st[i]=bt[i];
}
printf("Enter time quantum:");
scanf("%d",&tq);
while(1)
{
for(i=0,count=0;i<n;i++)
{
temp=tq;
if(st[i]==0)
{
count++;
continue;
}
if(st[i]>tq)
st[i]=st[i]-tq;
else
if(st[i]>=0)
{
temp=st[i];
st[i]=0;
}
sq=sq+temp;
tat[i]=sq;
}
if(n==count)
break;
}
for(i=0;i<n;i++)
{
wt[i]=tat[i]-bt[i];
swt=swt+wt[i];

14. stat=stat+tat[i];
}
awt=(float)swt/n;
atat=(float)stat/n;
printf("\nProcess_no\tBurst time\t Wait time\tTurn around time\n");
for(i=0;i<n;i++)
{
printf("\n%d\t\t%d\t\t%d\t\t\t%d",i+1,bt[i],wt[i],tat[i]);
}
printf("\nAvg wait time is= %f",awt);
printf("\nAvg turn around time is= %f",atat);
getch();
}

16. Program 6

Write a C program to implement banker’s algorithm.

#include<stdio.h>
#include<conio.h>
void main()
{
int k=0,output[10],d=0,t=0,ins[5],i,avail[5],allocated[10][5],need[10][5],MAX[10][5],pno,P[10],j,rz,
count=0;
clrscr();
printf("\n Enter the number of resources : ");
scanf("%d", &rz);
printf("\n enter the max instances of each resources\n");
for(i=0;i<rz;i++)
{ avail[i]=0;
printf("%c= ",(i+97));
scanf("%d",&ins[i]);
}
printf("\n Enter the number of processes : ");
scanf("%d", &pno);
printf("\n Enter the allocation matrix \n ");
for(i=0;i<rz;i++)
printf(" %c",(i+97));
printf("\n");
for(i=0;i <pno;i++)
{ P[i]=i;
printf("P[%d] ",P[i]);
for(j=0;j<rz;j++)
{
scanf("%d",&allocated[i][j]);
avail[j]+=allocated[i][j];
}
}
printf("\nEnter the MAX matrix \n ");
for(i=0;i<rz;i++)
{ printf(" %c",(i+97));
avail[i]=ins[i]-avail[i];
}
printf("\n");
for(i=0;i <pno;i++)
{
printf("P[%d] ",i);
for(j=0;j<rz;j++)
scanf("%d", &MAX[i][j]);
}

printf("\n");
A: d=-1;
for(i=0;i <pno;i++)
{ count=0; t=P[i];
for(j=0;j<rz;j++)
{
need[t][j] = MAX[t][j]-allocated[t][j];

17. if(need[t][j]<=avail[j])
count++;
}
if(count==rz)
{
output[k++]=P[i];
for(j=0;j<rz;j++)
avail[j]+=allocated[t][j];
}
else
P[++d]=P[i];
}
if(d!=-1)
{ pno=d+1;
goto A;
}
printf("\t <");
for(i=0;i<k;i++)
printf(" P[%d] ",output[i]);
printf(">");
getch();
}

19. Program 7

Write a C program to implement Producer-Consumer Problem.

#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
void display(int c,int stack[])
{
int i;
printf("\n----------------------------------------------------------\n");
if(c==0)
printf("\tStack is EMPTY\n\t\t(Now It is sleeping)");
else
for(i=1;i<=c;i++)
printf("\t%d",stack[i]);
printf("\n----------------------------------------------------------\n");
}
void main()
{
int ch,n,c1=0,c2=0,produce[23],consume[23];
clrscr();
printf("\n\n\n\n\n\n\n\t\tEnter Stack Size : ",n);
scanf("%d",&n);
while(1)
{
clrscr();
printf("\t\tProducer Stack (Stack Size : %d)\n\t\t~~~~~~~~~~~~~~~~~~~~~~",n);
display(c1,produce);
printf("\n\n\t\tConsumer Stack (Stack Size : %d)\n\t\t~~~~~~~~~~~~~~~~~~~~~~~",n);
display(c2,consume);
printf("\n\t\tCHOICES\n\t\t~~~~\n\t1.Producer\n\t2.Consumer\n\t3.Exit\nEnter your choice :
");
scanf("%d",&ch);
switch(ch)
{
case 1:
if(c1==n)
printf("Produer stack is FULL.So Producer goes to SLEEP\n");
else
{
c1++;
printf("\t\tEnter PRODUCE item is :");
scanf("%d",&produce[c1]);
}
break;
case 2:
if(c2==n)

20. printf("Consumer Stack is FULL.So it goes to SLEEP!.......\n\tReset the Cosumer
Stack\n",c2=0);
else if(c1==0)
printf("\tProducer stack is EMPTY\n");
else
{
c2++;
consume[c2]=produce[c1];
printf("\t\tCONSUME one item :");
c1--;
}
break;
case 3:
exit(0);
default:
printf("\tIt is Wrong choice,Please enter correct choice!............\n");
}
getch();
}
}

22. Program 8

Write a C program to implement Dekker’s Alogorithm.

#include<stdio.h>
#include<conio.h>
void main()
{
int choice;
int c1=1,c2=1,turn=1;
clrscr();
do
{
printf("\n1.Process 1 Enter");
printf("\n2.Process 2 Enter");
printf("\n3.Both Process Enter");
printf("\n4.Exit");
scanf("%d",&choice);
if(choice==1)
{
printf("\nProcess P1 Enters the Critical section");
c1=1;
turn=2;
}
else
printf("\nIt is the turn process P2");
c1=0;
while(c2==0)
{
if(turn==2)
c1=1;
}
while(turn==2);
c1=0;
if(choice==2)
{
printf("\nProcess P2 enters in critical section");
c2=1;
turn=1;
}
else
printf("\nIt is turn of Process P1");
c2=0;
while(c1==0)
{
if(turn==1)
c2=1;
}
while(turn==1);
c2=0;
}
while(choice!=4);
getch();

24. Program 9

Write a C program to implement LRU page replacement.

#include<stdio.h>
#include<conio.h>
int n,ref[100],fs,frame[100],count=0;
void input();
void show();
void cal();
void main()
{
clrscr();
input();
cal();
show();
getch();
}
void input()
{
int i;
printf("Enter no of pages in Refrence String\t");
scanf("%d",&n);
printf("Enter the reference string:");
for(i=0;i<n;i++)
scanf("%d",&ref[i]);
printf("Enter the Frame Size\t");
scanf("%d",&fs);
}
void cal()
{
int i,j,k=0,c1,c2[100],r,temp[100],t;
frame[k]=ref[k];
count++;
k++;
for(i=1;i<n;i++)
{
c1=0;
for(j=0;j<fs;j++)
{
if(ref[i]!=frame[j])
c1++;
}
if(c1==fs)
{
count++;
if(k<fs)
{
frame[k]=ref[i];

25. k++;
}
else
{
for(r=0;r<fs;r++)
{
c2[r]=0;
for(j-1;j<n;j--)
{
if(frame[r]!=ref[j])
c2[r]++;
else
break;
}
}
for(r=0;r<fs;r++)
temp[r]=c2[r];
for(r=0;r<fs;r++)
{
for(j=r;j<fs;j++)
{
if(temp[r]<temp[j])
{
t=temp[r];
temp[r]=temp[j];
temp[j]=t;
}
}
}
for(r=0;r<fs;r++)
{
if(c2[r]==temp[0])
frame[r]=ref[i];
}
}
}
}
}
void show()
{
printf("Page Faults = %d",count);
}

27. Program 10

Write a C program to implement FIFO page replacement.

#include<stdio.h>
#include<conio.h>
void main()
{
int ref[50],i,j,fault=0,count=0,frame[5],n;
int temp;
clrscr();
printf("\n Enter the no. of Frames :;");
scanf("%d",&n);
printf("\nEnter the reference string and end with -1 ::");
scanf("%d",&temp);
while(temp!=-1)
{
ref[count++]=temp;
scanf("%d",&temp);
}
for(i=0;i<n;i++)
frame[i]=-1;
for(i=0;i<count;i++)
{
for(j=0;j<n;j++)
if(frame[j]==ref[i])
break;
if(j==n)
{
frame[fault%n]=ref[i];
fault++;
}
printf("\n\n After inserting %2d the Frame status is ::",ref[i]);
for(j=0;j<n;j++)
printf("%4d",frame[j]);
}
printf("\n\n\t Total no. of page faults ::%d",fault);
getch();
}