Concept:
The FIFO page-replacement algorithm is easy to understand and program. However, its performance is not always good.
On the one hand, the page replaced may be an initialization module that was used a long time ago and is no longer needed.
On the other hand, it could contain a heavily used variable that was initialized early and is in constant use.
ALGORITHM:
1. Start
2. Read number of pages n
3. Read number of pages no
4. Read page numbers into an array a[i]
5. Initialize avail[i]=0 .to check page hit
6. Replace the page with circular queue, while re-placeing check page availability in the frame Place avail[i]=1 if page is placed in the frame Count page faults
7. Print the results.
8. Stop.
#include<stdio.h>
#include<conio.h>
int fr[3];
void main()
{
void display();
int i,j,page[12]={2,3,2,1,5,2,4,5,3,2,5,2};
int flag1=0,flag2=0,pf=0,frsize=3,top=0;
clrscr();
for(i=0;i<3;i++)
{
fr[i]=-1;
}
for(j=0;j<12;j++)
{
flag1=0;
flag2=0;
for(i=0;i<12;i++)
{
if(fr[i]==page[j])
{
flag1=1;
flag2=1;
break;
}
}
if(flag1==0)
{
for(i=0;i
{
if(fr[i]==-1)
{
fr[i]=page[j];
flag2=1;
break;
}
}
}
if(flag2==0)
{
fr[top]=page[j];
top++;
pf++;
if(top>=frsize)
top=0;
}
display();
}
printf("Number of page faults : %d ",pf);
getch();
}
void display()
{
int i;
printf("\n");
for(i=0;i<3;i++)
printf("%d\t",fr[i]);
}
OUTPUT : 2 -1 -1 2 3 -1 2 3 -1 2 3 1 5 3 1 5 2 1 5 2 4 5 2 4 3 2 4 3 2 4 3 5 4 3 5 2 Number of page faults : 6