OS Exam practical
Q.1 : Write a program using c to copy files using system call.
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#define BUF_SIZE 4096
int main(int argc, char *argv[]) {
int source_fd, dest_fd;
ssize_t num_read;
char buf[BUF_SIZE];
if (argc != 3) {
fprintf(stderr, "Usage: %s <source> <destination>\n", argv[0]);
exit(EXIT_FAILURE);
}
source_fd = open(argv[1], O_RDONLY);
if (source_fd == -1) {
perror("open");
exit(EXIT_FAILURE);
}
dest_fd = open(argv[2], O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
if (dest_fd == -1) {
perror("open");
exit(EXIT_FAILURE);
}
while ((num_read = read(source_fd, buf, BUF_SIZE)) > 0) {
if (write(dest_fd, buf, num_read) != num_read) {
perror("write");
exit(EXIT_FAILURE);
}
}
if (num_read == -1) {
perror("read");
exit(EXIT_FAILURE);
}
if (close(source_fd) == -1) {
perror("close");
exit(EXIT_FAILURE);
}
if (close(dest_fd) == -1) {
perror("close");
exit(EXIT_FAILURE);
}
printf("File copied successfully!\n");
exit(EXIT_SUCCESS);
}
Q.2: Write a program using c to implement fcfs scheduling algorithm.
#include<stdio.h>
void findWaitingTime(int processes[], int n, int bt[], int wt[]) {
wt[0] = 0;
for (int i = 1; i < n; i++) {
wt[i] = wt[i - 1] + bt[i - 1];
}
}
void findTurnAroundTime(int processes[], int n, int bt[], int wt[], int tat[]) {
for (int i = 0; i < n; i++) {
tat[i] = bt[i] + wt[i];
}
}
void findAverageTime(int processes[], int n, int bt[]) {
int wt[n], tat[n];
int total_wt = 0, total_tat = 0;
findWaitingTime(processes, n, bt, wt);
findTurnAroundTime(processes, n, bt, wt, tat);
printf("Process Burst Time Waiting Time Turn-Around Time\n");
for (int i = 0; i < n; i++) {
total_wt += wt[i];
total_tat += tat[i];
printf("%d\t\t%d\t\t%d\t\t%d\n", i + 1, bt[i], wt[i], tat[i]);
}
printf("Average waiting time = %.2f\n", (float)total_wt / (float)n);
printf("Average turn-around time = %.2f\n", (float)total_tat / (float)n);
}
int main() {
int processes[] = {1, 2, 3};
int n = sizeof processes / sizeof processes[0];
int burst_time[] = {10, 5, 8};
findAverageTime(processes, n, burst_time);
return 0;
}
Q.3: Write a program using c to implement non preemptive priority based scheduling algorithm.
#include<stdio.h>
void findWaitingTime(int processes[], int n, int bt[], int wt[], int priority[]) {
int service_time[n];
service_time[0] = 0;
wt[0] = 0;
for (int i = 1; i < n; i++) {
service_time[i] = service_time[i - 1] + bt[i - 1];
wt[i] = service_time[i] - service_time[i - 1];
}
}
void findTurnAroundTime(int processes[], int n, int bt[], int wt[], int tat[]) {
for (int i = 0; i < n; i++) {
tat[i] = bt[i] + wt[i];
}
}
void findAverageTime(int processes[], int n, int bt[], int priority[]) {
int wt[n], tat[n];
int total_wt = 0, total_tat = 0;
findWaitingTime(processes, n, bt, wt, priority);
findTurnAroundTime(processes, n, bt, wt, tat);
printf("Process Burst Time Priority Waiting Time Turn-Around Time\n");
for (int i = 0; i < n; i++) {
total_wt += wt[i];
total_tat += tat[i];
printf("%d\t\t%d\t\t%d\t\t%d\t\t%d\n", i + 1, bt[i], priority[i], wt[i], tat[i]);
}
printf("Average waiting time = %.2f\n", (float)total_wt / (float)n);
printf("Average turn-around time = %.2f\n", (float)total_tat / (float)n);
}
void sortProcessesByPriority(int processes[], int bt[], int priority[], int n) {
for (int i = 0; i < n - 1; i++) {
for (int j = 0; j < n - i - 1; j++) {
if (priority[j] > priority[j + 1]) {
int temp = processes[j];
processes[j] = processes[j + 1];
processes[j + 1] = temp;
temp = bt[j];
bt[j] = bt[j + 1];
bt[j + 1] = temp;
temp = priority[j];
priority[j] = priority[j + 1];
priority[j + 1] = temp;
}
}
}
}
int main() {
int processes[] = {1, 2, 3};
int n = sizeof processes / sizeof processes[0];
int burst_time[] = {10, 5, 8};
int priority[] = {3, 1, 2};
sortProcessesByPriority(processes, burst_time, priority, n);
findAverageTime(processes, n, burst_time, priority);
return 0;
}
Q.4: Write a program using c to implement round Robin scheduling algorithm.
#include <stdio.h>
void findWaitingTime(int processes[], int n, int bt[], int wt[], int quantum) {
int remaining_bt[n];
for (int i = 0; i < n; i++) {
remaining_bt[i] = bt[i];
}
int t = 0; // Current time
while (1) {
int done = 1; // Flag to indicate if all processes are done
for (int i = 0; i < n; i++) {
if (remaining_bt[i] > 0) {
done = 0; // At least one process is not done
if (remaining_bt[i] > quantum) {
t += quantum;
remaining_bt[i] -= quantum;
} else {
t += remaining_bt[i];
wt[i] = t - bt[i]; // Waiting time = current time - burst time
remaining_bt[i] = 0;
}
}
}
if (done == 1) // All processes are done
break;
}
}
void findTurnAroundTime(int processes[], int n, int bt[], int wt[], int tat[]) {
for (int i = 0; i < n; i++) {
tat[i] = bt[i] + wt[i];
}
}
void findAverageTime(int processes[], int n, int bt[], int quantum) {
int wt[n], tat[n];
int total_wt = 0, total_tat = 0;
findWaitingTime(processes, n, bt, wt, quantum);
findTurnAroundTime(processes, n, bt, wt, tat);
printf("Process Burst Time Waiting Time Turn-Around Time\n");
for (int i = 0; i < n; i++) {
total_wt += wt[i];
total_tat += tat[i];
printf("%d\t\t%d\t\t%d\t\t%d\n", i + 1, bt[i], wt[i], tat[i]);
}
printf("Average waiting time = %.2f\n", (float)total_wt / (float)n);
printf("Average turn-around time = %.2f\n", (float)total_tat / (float)n);
}
int main() {
int processes[] = {1, 2, 3, 4};
int n = sizeof processes / sizeof processes[0];
int burst_time[] = {10, 5, 8, 12};
int quantum = 2;
findAverageTime(processes, n, burst_time, quantum);
return 0;
}
Q.5: Write a program using c to implement sktf scheduling algorithm.
#include<stdio.h>
#include<limits.h>
void findWaitingTime(int processes[], int n, int bt[], int wt[]) {
int rt[n]; // Remaining time
// Initialize remaining time as burst time
for (int i = 0; i < n; i++) {
rt[i] = bt[i];
}
int complete = 0, t = 0, min = INT_MAX;
int shortest = 0, finish_time;
int check = 0; // Check if the loop breaks
// Process until all processes are done
while (complete != n) {
// Find the process with minimum remaining burst time
for (int j = 0; j < n; j++) {
if ((rt[j] <= t) && (rt[j] < min) && (rt[j] > 0)) {
min = rt[j];
shortest = j;
check = 1;
}
}
if (check == 0) {
t++;
continue;
}
// Reduce remaining burst time
rt[shortest]--;
min = rt[shortest];
if (min == 0)
min = INT_MAX;
// If a process is finished
if (rt[shortest] == 0) {
complete++;
check = 0;
finish_time = t + 1;
wt[shortest] = finish_time - bt[shortest];
if (wt[shortest] < 0)
wt[shortest] = 0;
}
// Move to the next time slot
t++;
}
}
void findTurnAroundTime(int processes[], int n, int bt[], int wt[], int tat[]) {
// Turnaround time = Burst time + Waiting time
for (int i = 0; i < n; i++) {
tat[i] = bt[i] + wt[i];
}
}
void findAverageTime(int processes[], int n, int bt[]) {
int wt[n], tat[n];
int total_wt = 0, total_tat = 0;
findWaitingTime(processes, n, bt, wt);
findTurnAroundTime(processes, n, bt, wt, tat);
printf("Process Burst Time Waiting Time Turn-Around Time\n");
for (int i = 0; i < n; i++) {
total_wt += wt[i];
total_tat += tat[i];
printf("%d\t\t%d\t\t%d\t\t%d\n", i + 1, bt[i], wt[i], tat[i]);
}
printf("Average waiting time = %.2f\n", (float)total_wt / (float)n);
printf("Average turn-around time = %.2f\n", (float)total_tat / (float)n);
}
int main() {
int processes[] = {1, 2, 3};
int n = sizeof processes / sizeof processes[0];
int burst_time[] = {6, 8, 7};
findAverageTime(processes, n, burst_time);
return 0;
}
Q.6: What is Unix operating system? Explain different types of commands?
Unix is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, developed in the 1970s. It's a powerful, stable, and versatile operating system primarily used in servers and workstations. Unix systems are known for their robustness, scalability, and support for multitasking and multiuser functionality.
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