VNR VJIET Name of the experiment:
Name of the Laboratory: Page Replacement Algorithms
Operating Systems Laboratory Experiment No: 6
Implementation of the following Page Replacement Algorithms a) FIFO b)
LRU c) optimal
a) FIFO
#include <stdio.h>
#include <conio.h>
void main() {
int i, j, n, a[50], frame[10], avail, count = 0, no;
clrscr();
printf("Enter the number of pages: ");
scanf("%d", &n);
printf("Enter the page numbers: ");
for (i = 0; i < n; i++) {
scanf("%d", &a[i]);
}
printf("Enter the number of frames: ");
scanf("%d", &no);
for (i = 0; i < no; i++) {
frame[i] = -1;
}
j = 0;
printf("\nRef String \t Page Frames\n");
for (i = 0; i < n; i++) {
printf("%d\t\t", a[i]);
avail = 0;
for (int k = 0; k < no; k++) {
if (frame[k] == a[i]) {
avail = 1;
break;
}
}
if (avail == 0) {
frame[j] = a[i];
j = (j + 1) % no;
count++;
}
for (int k = 0; k < no; k++) {
if (frame[k] != -1)
printf("%d\t", frame[k]);
else
printf("-\t");
}
printf("\n");
}
printf("\nTotal page faults: %d\n", count);
}
Output-
VNR VJIET Name of the experiment:
Name of the Laboratory: Page Replacement Algorithms
Operating Systems Laboratory Experiment No: 6
b) optimal
#include <stdio.h>
int main() {
int F, P, frames[10], a[30], temp[10];
int flag1, flag2, flag3, i, j, k, pos, max, faults = 0;
printf("Enter Number of Frames: ");
scanf("%d", &F);
printf("Enter Number of Pages: ");
scanf("%d", &P);
printf("Enter Page Reference String: ");
for (i = 0; i < P; i++) {
scanf("%d", &a[i]);
}
for (i = 0; i < F; i++) {
frames[i] = -1;
}
printf("\nReference String \t Page Frames\n");
for (i = 0; i < P; i++) {
printf("%d\t\t", a[i]);
flag1 = flag2 = 0;
for (j = 0; j < F; j++) {
if (frames[j] == a[i]) {
flag1 = flag2 = 1;
break;
}
}
if (flag1 == 0) {
for (j = 0; j < F; j++) {
if (frames[j] == -1) {
frames[j] = a[i];
flag2 = 1;
faults++;
break;
}
}
}
if (flag2 == 0) {
flag3 = 0;
for (j = 0; j < F; j++) {
temp[j] = -1;
for (k = i + 1; k < P; k++) {
if (frames[j] == a[k]) {
temp[j] = k;
break;
}
}
}
for (j = 0; j < F; j++) {
if (temp[j] == -1) {
pos = j;
flag3 = 1;
break;
}
}
if (flag3 == 0) {
max = temp[0];
pos = 0;
for (j = 1; j < F; j++) {
if (temp[j] > max) {
max = temp[j];
pos = j;
}
}
}
frames[pos] = a[i];
faults++;
}
for (j = 0; j < F; j++) {
if (frames[j] != -1)
printf("%d\t", frames[j]);
else
printf("-\t");
}
printf("\n");
}
printf("\nTotal Page Faults: %d\n", faults);
return 0;
}
VNR VJIET Name of the experiment:
Name of the Laboratory: Page Replacement Algorithms
Operating Systems Laboratory Experiment No: 6
Output-
c) LRU
#include <stdio.h>
int main() {
int a[20], p[50], c = 0, c1, d, f, k = 0, n, o, t, b[20], c2[20];
int i, j, r;
printf("Enter number of pages: ");
scanf("%d", &n);
printf("Enter the reference string: ");
for (i = 0; i < n; i++)
scanf("%d", &p[i]);
printf("Enter number of frames: ");
scanf("%d", &f);
printf("\n");
for (i = 0; i < f; i++)
a[i] = -1; // Initialize frames
for (i = 0; i < n; i++) {
c1 = 0;
for (j = 0; j < f; j++) {
if (a[j] == p[i]) {
c1 = 1;
break;
}
}
if (c1 == 0) {
if (k < f) {
a[k] = p[i];
k++;
} else {
int max = -1, pos = -1;
for (r = 0; r < f; r++) {
c2[r] = 0;
for (j = i + 1; j < n; j++) {
if (a[r] == p[j])
break;
c2[r]++;
}
if (c2[r] > max) {
max = c2[r];
pos = r;
}
}
a[pos] = p[i];
}
c++;
}
for (j = 0; j < f; j++)
printf("%d\t", a[j]);
printf("\n");
}
printf("Total page faults: %d\n", c);
return 0;
}
VNR VJIET Name of the experiment:
Name of the Laboratory: Page Replacement Algorithms
Operating Systems Laboratory Experiment No: 6
Output-
