Write the simulation program to implement demand paging and show the page scheduling and total number of page faults according to the LRU page replacement algorithm. Assume the memory of n frames.
Reference String : 3, 4, 5, 4, 3, 4, 7, 2, 4, 5, 6, 7, 2, 4, 6
#include <stdio.h>
#include <stdlib.h>
#define MAX_FRAMES 100
#define REFERENCE_STRING_LENGTH 15
void printFrames(int frames[], int frame_count) {
for (int i = 0; i < frame_count; i++) {
if (frames[i] != -1)
printf("%d ", frames[i]);
else
printf("X ");
}
printf("\n");
}
int isInFrames(int frames[], int frame_count, int page) {
for (int i = 0; i < frame_count; i++) {
if (frames[i] == page) {
return 1;
}
}
return 0;
}
int findLRUIndex(int timestamps[], int frame_count) {
int min = timestamps[0];
int min_index = 0;
for (int i = 1; i < frame_count; i++) {
if (timestamps[i] < min) {
min = timestamps[i];
min_index = i;
}
}
return min_index;
}
void lruPageReplacement(int reference_string[], int ref_len, int frame_count) {
int frames[MAX_FRAMES];
int timestamps[MAX_FRAMES];
int page_faults = 0;
int time = 0;
// Initialize frames and timestamps
for (int i = 0; i < frame_count; i++) {
frames[i] = -1;
timestamps[i] = 0;
}
for (int i = 0; i < ref_len; i++) {
int page = reference_string[i];
// Check if page is already in frames
if (isInFrames(frames, frame_count, page)) {
// Update timestamp
for (int j = 0; j < frame_count; j++) {
if (frames[j] == page) {
timestamps[j] = time++;
break;
}
}
printf("Page %d is already in frames. No page fault.\n", page);
} else {
// Page fault occurred
page_faults++;
int replace_index = findLRUIndex(timestamps, frame_count);
frames[replace_index] = page;
timestamps[replace_index] = time++;
printf("Page %d caused a page fault. Replacing page in frame %d.\n", page, replace_index);
}
// Print current state of frames
printFrames(frames, frame_count);
}
printf("Total number of page faults: %d\n", page_faults);
}
int main() {
int reference_string[REFERENCE_STRING_LENGTH] = {3, 4, 5, 4, 3, 4, 7, 2, 4, 5, 6, 7, 2, 4, 6};
int frame_count;
printf("Enter the number of frames: ");
scanf("%d", &frame_count);
if (frame_count > MAX_FRAMES || frame_count <= 0) {
printf("Invalid number of frames. Must be between 1 and %d.\n", MAX_FRAMES);
return 1;
}
lruPageReplacement(reference_string, REFERENCE_STRING_LENGTH, frame_count);
return 0;
}
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