modified and updated

OS/C/Week10/qq1.c

@@ -0,0 +1,176 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+// Function to check if a page exists in frames
+bool isPagePresent(int* frames, int num_frames, int page) {
+    for (int i = 0; i < num_frames; i++) {
+        if (frames[i] == page) {
+            return true;
+        }
+    }
+    return false;
+}
+
+// FIFO Page Replacement Algorithm
+void fifo(int* reference_string, int num_pages, int num_frames) {
+    int* frames = (int*)malloc(num_frames * sizeof(int));
+    int page_faults = 0;
+    int frame_index = 0;
+
+    // Initialize frames with -1 (indicating empty)
+    for (int i = 0; i < num_frames; i++) {
+        frames[i] = -1;
+    }
+
+    printf("\nFIFO Page Replacement Algorithm:\n");
+    printf("Reference String: ");
+    for (int i = 0; i < num_pages; i++) {
+        printf("%d ", reference_string[i]);
+    }
+    printf("\n\n");
+
+    for (int i = 0; i < num_pages; i++) {
+        printf("Page %d: ", reference_string[i]);
+
+        // Check if page already exists in frames
+        if (!isPagePresent(frames, num_frames, reference_string[i])) {
+            // Replace page at current frame_index
+            frames[frame_index] = reference_string[i];
+            frame_index = (frame_index + 1) % num_frames;
+            page_faults++;
+
+            printf("Page Fault! Frames: ");
+        } else {
+            printf("No Page Fault. Frames: ");
+        }
+
+        // Print current state of frames
+        for (int j = 0; j < num_frames; j++) {
+            if (frames[j] == -1) {
+                printf("[ ] ");
+            } else {
+                printf("[%d] ", frames[j]);
+            }
+        }
+        printf("\n");
+    }
+
+    printf("\nTotal Page Faults (FIFO): %d\n", page_faults);
+    free(frames);
+}
+
+// Function to find index of page that will be used farthest in future
+int findOptimalPage(int* reference_string, int* frames, int num_frames, int num_pages, int current_position) {
+    int farthest = -1;
+    int index = -1;
+
+    for (int i = 0; i < num_frames; i++) {
+        int j;
+        for (j = current_position + 1; j < num_pages; j++) {
+            if (frames[i] == reference_string[j]) {
+                if (j > farthest) {
+                    farthest = j;
+                    index = i;
+                }
+                break;
+            }
+        }
+
+        // If page is never used in future
+        if (j == num_pages) {
+            return i;
+        }
+    }
+
+    // If all pages will be used in future, return the one used farthest
+    return (index == -1) ? 0 : index;
+}
+
+// Optimal Page Replacement Algorithm
+void optimal(int* reference_string, int num_pages, int num_frames) {
+    int* frames = (int*)malloc(num_frames * sizeof(int));
+    int page_faults = 0;
+
+    // Initialize frames with -1 (indicating empty)
+    for (int i = 0; i < num_frames; i++) {
+        frames[i] = -1;
+    }
+
+    printf("\nOptimal Page Replacement Algorithm:\n");
+    printf("Reference String: ");
+    for (int i = 0; i < num_pages; i++) {
+        printf("%d ", reference_string[i]);
+    }
+    printf("\n\n");
+
+    for (int i = 0; i < num_pages; i++) {
+        printf("Page %d: ", reference_string[i]);
+
+        // Check if page already exists in frames
+        if (!isPagePresent(frames, num_frames, reference_string[i])) {
+            int free_frame = -1;
+
+            // Check if there's an empty frame
+            for (int j = 0; j < num_frames; j++) {
+                if (frames[j] == -1) {
+                    free_frame = j;
+                    break;
+                }
+            }
+
+            if (free_frame != -1) {
+                // If empty frame exists, use it
+                frames[free_frame] = reference_string[i];
+            } else {
+                // Find optimal page to replace
+                int replace_index = findOptimalPage(reference_string, frames, num_frames, num_pages, i);
+                frames[replace_index] = reference_string[i];
+            }
+
+            page_faults++;
+            printf("Page Fault! Frames: ");
+        } else {
+            printf("No Page Fault. Frames: ");
+        }
+
+        // Print current state of frames
+        for (int j = 0; j < num_frames; j++) {
+            if (frames[j] == -1) {
+                printf("[ ] ");
+            } else {
+                printf("[%d] ", frames[j]);
+            }
+        }
+        printf("\n");
+    }
+
+    printf("\nTotal Page Faults (Optimal): %d\n", page_faults);
+    free(frames);
+}
+
+int main() {
+    int num_pages, num_frames;
+
+    printf("Enter number of frames: ");
+    scanf("%d", &num_frames);
+
+    printf("Enter number of pages in reference string: ");
+    scanf("%d", &num_pages);
+
+    int* reference_string = (int*)malloc(num_pages * sizeof(int));
+
+    printf("Enter the reference string (page numbers):\n");
+    for (int i = 0; i < num_pages; i++) {
+        scanf("%d", &reference_string[i]);
+    }
+
+    // Run FIFO algorithm
+    fifo(reference_string, num_pages, num_frames);
+
+    // Run Optimal algorithm
+    optimal(reference_string, num_pages, num_frames);
+
+    free(reference_string);
+    return 0;
+}