modified and updated
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2 changed files with 345 additions and 0 deletions
169
OS/C/Week10/q2.c
169
OS/C/Week10/q2.c
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#include <stdio.h>
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#include <stdlib.h>
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#include <limits.h> // For INT_MAX
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// Structure to represent a frame and its last used time
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typedef struct {
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int page_number;
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int last_used_time;
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} Frame;
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// Function to find if a page exists in frames and return its index
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// Also updates the last_used_time if found
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int find_page(Frame frames[], int n_frames, int page, int current_time) {
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for (int i = 0; i < n_frames; i++) {
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if (frames[i].page_number == page) {
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frames[i].last_used_time = current_time; // Update time on hit
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return i; // Page found (Hit)
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}
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}
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return -1; // Page not found (Fault)
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}
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// Function to find the index of the Least Recently Used (LRU) page
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int find_lru_index(Frame frames[], int n_frames) {
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int min_time = INT_MAX;
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int lru_index = 0;
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for (int i = 0; i < n_frames; i++) {
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// Frame must contain a valid page (not -1)
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if (frames[i].page_number != -1 && frames[i].last_used_time < min_time) {
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min_time = frames[i].last_used_time;
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lru_index = i;
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}
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}
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return lru_index;
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}
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// Function to print the current state of frames
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void print_frames(Frame frames[], int n_frames) {
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printf("[");
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for (int i = 0; i < n_frames; i++) {
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if (frames[i].page_number == -1) {
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printf(" - ");
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} else {
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printf(" %d ", frames[i].page_number);
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}
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}
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printf("]\n");
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}
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int main() {
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int n_frames, n_pages;
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int *pages = NULL; // Reference string
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Frame *frames = NULL; // Frames in memory
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int page_faults = 0;
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int page_hits = 0;
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int current_time = 0; // Counter to track usage time
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int frame_idx = 0; // Index for filling empty frames initially
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// 1. Get Inputs
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printf("Enter the number of frames: ");
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if (scanf("%d", &n_frames) != 1 || n_frames <= 0) {
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fprintf(stderr, "Error: Invalid number of frames.\n");
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return 1;
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}
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printf("Enter the number of pages in the reference string: ");
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if (scanf("%d", &n_pages) != 1 || n_pages <= 0) {
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fprintf(stderr, "Error: Invalid number of pages.\n");
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return 1;
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}
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// 2. Allocate Memory
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pages = (int *)malloc(n_pages * sizeof(int));
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if (pages == NULL) {
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perror("Failed to allocate memory for pages");
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return 1;
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}
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frames = (Frame *)malloc(n_frames * sizeof(Frame));
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if (frames == NULL) {
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perror("Failed to allocate memory for frames");
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free(pages); // Clean up already allocated memory
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return 1;
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}
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printf("Enter the page reference string (space-separated %d integers):\n", n_pages);
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for (int i = 0; i < n_pages; i++) {
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if (scanf("%d", &pages[i]) != 1) {
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fprintf(stderr, "Error reading page reference string.\n");
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free(pages);
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free(frames);
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return 1;
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}
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}
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// 3. Initialize Frames
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for (int i = 0; i < n_frames; i++) {
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frames[i].page_number = -1; // -1 indicates empty frame
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frames[i].last_used_time = -1; // Initialize time
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}
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printf("\n--- LRU Simulation Start ---\n");
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printf("Frames: %d | Reference String Length: %d\n\n", n_frames, n_pages);
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// 4. Process Page References
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for (int i = 0; i < n_pages; i++) {
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current_time++; // Increment time step for each reference
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int current_page = pages[i];
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printf("Ref: %d -> ", current_page);
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int found_index = find_page(frames, n_frames, current_page, current_time);
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if (found_index != -1) {
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// Page Hit
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page_hits++;
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printf("Hit ");
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} else {
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// Page Fault
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page_faults++;
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printf("Fault ");
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// Find a place for the new page
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int replace_index = -1;
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// Check for an empty frame first
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for(int k=0; k < n_frames; k++){
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if(frames[k].page_number == -1){
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replace_index = k;
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break;
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}
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}
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if (replace_index != -1) {
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// Use the empty frame
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frames[replace_index].page_number = current_page;
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frames[replace_index].last_used_time = current_time;
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printf("(loaded into empty frame %d) ", replace_index);
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} else {
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// No empty frames, find LRU page to replace
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replace_index = find_lru_index(frames, n_frames);
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printf("(replaced P%d in frame %d) ", frames[replace_index].page_number, replace_index);
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frames[replace_index].page_number = current_page;
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frames[replace_index].last_used_time = current_time;
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}
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}
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print_frames(frames, n_frames); // Show frame status after each step
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}
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// 5. Output Results
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printf("\n--- LRU Simulation End ---\n");
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printf("Total Page References: %d\n", n_pages);
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printf("Total Page Hits: %d\n", page_hits);
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printf("Total Page Faults: %d\n", page_faults);
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if (n_pages > 0) {
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printf("Hit Rate: %.2f%%\n", (double)page_hits / n_pages * 100.0);
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printf("Fault Rate: %.2f%%\n", (double)page_faults / n_pages * 100.0);
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} else {
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printf("Hit Rate: N/A\n");
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printf("Fault Rate: N/A\n");
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}
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// 6. Free Memory
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free(pages);
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free(frames);
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return 0;
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}
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176
OS/C/Week10/qq1.c
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176
OS/C/Week10/qq1.c
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#include <stdio.h>
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#include <stdlib.h>
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#include <stdbool.h>
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// Function to check if a page exists in frames
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bool isPagePresent(int* frames, int num_frames, int page) {
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for (int i = 0; i < num_frames; i++) {
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if (frames[i] == page) {
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return true;
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}
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}
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return false;
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}
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// FIFO Page Replacement Algorithm
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void fifo(int* reference_string, int num_pages, int num_frames) {
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int* frames = (int*)malloc(num_frames * sizeof(int));
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int page_faults = 0;
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int frame_index = 0;
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// Initialize frames with -1 (indicating empty)
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for (int i = 0; i < num_frames; i++) {
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frames[i] = -1;
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}
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printf("\nFIFO Page Replacement Algorithm:\n");
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printf("Reference String: ");
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for (int i = 0; i < num_pages; i++) {
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printf("%d ", reference_string[i]);
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}
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printf("\n\n");
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for (int i = 0; i < num_pages; i++) {
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printf("Page %d: ", reference_string[i]);
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// Check if page already exists in frames
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if (!isPagePresent(frames, num_frames, reference_string[i])) {
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// Replace page at current frame_index
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frames[frame_index] = reference_string[i];
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frame_index = (frame_index + 1) % num_frames;
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page_faults++;
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printf("Page Fault! Frames: ");
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} else {
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printf("No Page Fault. Frames: ");
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}
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// Print current state of frames
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for (int j = 0; j < num_frames; j++) {
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if (frames[j] == -1) {
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printf("[ ] ");
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} else {
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printf("[%d] ", frames[j]);
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}
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}
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printf("\n");
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}
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printf("\nTotal Page Faults (FIFO): %d\n", page_faults);
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free(frames);
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}
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// Function to find index of page that will be used farthest in future
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int findOptimalPage(int* reference_string, int* frames, int num_frames, int num_pages, int current_position) {
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int farthest = -1;
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int index = -1;
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for (int i = 0; i < num_frames; i++) {
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int j;
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for (j = current_position + 1; j < num_pages; j++) {
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if (frames[i] == reference_string[j]) {
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if (j > farthest) {
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farthest = j;
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index = i;
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}
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break;
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}
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}
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// If page is never used in future
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if (j == num_pages) {
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return i;
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}
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}
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// If all pages will be used in future, return the one used farthest
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return (index == -1) ? 0 : index;
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}
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// Optimal Page Replacement Algorithm
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void optimal(int* reference_string, int num_pages, int num_frames) {
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int* frames = (int*)malloc(num_frames * sizeof(int));
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int page_faults = 0;
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// Initialize frames with -1 (indicating empty)
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for (int i = 0; i < num_frames; i++) {
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frames[i] = -1;
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}
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printf("\nOptimal Page Replacement Algorithm:\n");
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printf("Reference String: ");
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for (int i = 0; i < num_pages; i++) {
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printf("%d ", reference_string[i]);
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}
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printf("\n\n");
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for (int i = 0; i < num_pages; i++) {
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printf("Page %d: ", reference_string[i]);
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// Check if page already exists in frames
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if (!isPagePresent(frames, num_frames, reference_string[i])) {
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int free_frame = -1;
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// Check if there's an empty frame
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for (int j = 0; j < num_frames; j++) {
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if (frames[j] == -1) {
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free_frame = j;
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break;
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}
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}
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if (free_frame != -1) {
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// If empty frame exists, use it
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frames[free_frame] = reference_string[i];
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} else {
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// Find optimal page to replace
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int replace_index = findOptimalPage(reference_string, frames, num_frames, num_pages, i);
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frames[replace_index] = reference_string[i];
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}
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page_faults++;
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printf("Page Fault! Frames: ");
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} else {
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printf("No Page Fault. Frames: ");
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}
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// Print current state of frames
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for (int j = 0; j < num_frames; j++) {
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if (frames[j] == -1) {
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printf("[ ] ");
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} else {
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printf("[%d] ", frames[j]);
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}
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}
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printf("\n");
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}
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printf("\nTotal Page Faults (Optimal): %d\n", page_faults);
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free(frames);
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}
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int main() {
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int num_pages, num_frames;
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printf("Enter number of frames: ");
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scanf("%d", &num_frames);
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printf("Enter number of pages in reference string: ");
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scanf("%d", &num_pages);
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int* reference_string = (int*)malloc(num_pages * sizeof(int));
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printf("Enter the reference string (page numbers):\n");
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for (int i = 0; i < num_pages; i++) {
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scanf("%d", &reference_string[i]);
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}
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// Run FIFO algorithm
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fifo(reference_string, num_pages, num_frames);
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// Run Optimal algorithm
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optimal(reference_string, num_pages, num_frames);
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free(reference_string);
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return 0;
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}
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