Write the following java code in C code.

import java.util.concurrent.Semaphore; import java.util.Random;

public class Main { public static void main(String[] args) { // Number of students. int numberofStudents = 5; // Create semaphores. SignalSemaphore wakeup = new SignalSemaphore(); Semaphore chairs = new Semaphore(3); Semaphore available = new Semaphore(1); // Used for randomly generating program time. Random studentWait = new Random(); // Create student threads and start them. for (int i = 0; i < numberofStudents; i++) { Thread student = new Thread(new Student(studentWait.nextInt(20), wakeup, chairs, available, i+1)); student.start(); } // Create and start TA Thread. Thread ta = new Thread(new TeachingAssistant(wakeup, chairs, available)); ta.start(); } }

/** * This semaphore implementation is used to "wakeup" the TA. */ class SignalSemaphore { private boolean signal = false;

// Used to send the signal. public synchronized void take() { this.signal = true; this.notify(); }

// Will wait until it receives a signal before continuing. public synchronized void release() throws InterruptedException{ while(!this.signal) wait(); this.signal = false; } }

/** This is the student thread. It will alternate between programming and seeking help from the TA. */ class Student implements Runnable { // Time to program before asking for help (in seconds). private int programTime; // Student number. private int studentNum;

// Semaphore used to wakeup TA. private SignalSemaphore wakeup;

// Semaphore used to wait in chairs outside office. private Semaphore chairs;

// Mutex lock (binary semaphore) used to determine if TA is available. private Semaphore available;

// A reference to the current thread. private Thread t;

// Non-default constructor. public Student(int program, SignalSemaphore w, Semaphore c, Semaphore a, int num) { programTime = program; wakeup = w; chairs = c; available = a; studentNum = num; t = Thread.currentThread(); }

/** * The run method will infinitely loop between programming and * asking for help until the thread is interrupted. */ @Override public void run() { // Infinite loop. while(true) { try { // Program first. System.out.println("Student " + studentNum + " has started programming for " + programTime + " seconds."); t.sleep(programTime * 1000); // Check to see if TA is available first. System.out.println("Student " + studentNum + " is checking to see if TA is available."); if (available.tryAcquire()) { try { // Wakeup the TA. wakeup.take(); System.out.println("Student " + studentNum + " has woke up the TA."); System.out.println("Student " + studentNum + " has started working with the TA."); t.sleep(5000); System.out.println("Student " + studentNum + " has stopped working with the TA."); } catch (InterruptedException e) { // Something bad happened. continue; } finally { available.release(); } } else { // Check to see if any chairs are available. System.out.println("Student " + studentNum + " could not see the TA. Checking for available chairs."); if (chairs.tryAcquire()) { try { // Wait for TA to finish with other student. System.out.println("Student " + studentNum + " is sitting outside the office. " + "He is #" + ((3 - chairs.availablePermits())) + " in line."); available.acquire(); System.out.println("Student " + studentNum + " has started working with the TA."); t.sleep(5000); System.out.println("Student " + studentNum + " has stopped working with the TA."); available.release(); } catch (InterruptedException e) { // Something bad happened. continue; } } else { System.out.println("Student " + studentNum + " could not see the TA and all chairs were taken. Back to programming!"); } } } catch (InterruptedException e) { break; } } } }

/** * * */ class TeachingAssistant implements Runnable { // Semaphore used to wakeup TA. private SignalSemaphore wakeup;

// Semaphore used to wait in chairs outside office. private Semaphore chairs;

// Mutex lock (binary semaphore) used to determine if TA is available. private Semaphore available;

// A reference to the current thread. private Thread t; public TeachingAssistant(SignalSemaphore w, Semaphore c, Semaphore a) { t = Thread.currentThread(); wakeup = w; chairs = c; available = a; } @Override public void run() { while (true) { try { System.out.println("No students left. The TA is going to nap."); wakeup.release(); System.out.println("The TA was awoke by a student."); t.sleep(5000); // If there are other students waiting. if (chairs.availablePermits() != 3) { do { t.sleep(5000); chairs.release(); } while (chairs.availablePermits() != 3); } } catch (InterruptedException e) { // Something bad happened. continue; } } } }