OS20

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
int main() {
pid_t child_pid = fork();
if (child_pid < 0) {
perror("Fork failed");
exit(1);}
if (child_pid == 0) {
execl("/bin/ls", "ls", NULL);
perror("Execl failed");
exit(1);
} else {
printf("Parent process is going to sleep for 3 seconds...\n");
sleep(3);
wait(NULL);
printf("Parent process has woken up.\n");}
return 0;}

#2
#include <stdio.h>
#include <stdlib.h>
int findLRU(int frames[], int n, int page, int current) {
int index = -1;
int farthest = current;
for (int i = 0; i < n; i++) {
int j;
for (j = current - 1; j >= 0; j--) {
if (frames[i] == page) {
break;}
if (frames[i] == -1 || frames[i] == frames[j]) {
if (j < farthest) {
farthest = j;
index = i;}
break;}}}
return index;}
int main() {
int n = 3;
int referenceString[] = {7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3, 2};
int referenceStringLength = sizeof(referenceString) / sizeof(referenceString[0]);
int frames[n];
int pageFaults = 0;
for (int i = 0; i < n; i++) {
frames[i] = -1;}
printf("Page Scheduling using LRU:\n");
for (int i = 0; i < referenceStringLength; i++) {
int page = referenceString[i];
int found = 0;
for (int j = 0; j < n; j++) {
if (frames[j] == page) {
found = 1;
break;}}
if (!found) {
int replaceIndex = findLRU(frames, n, page, i);
frames[replaceIndex] = page;
pageFaults++;
printf("Page %d -> Page Fault\n", page);}}
printf("Total Page Faults: %d\n", pageFaults);
return 0;