currentReaders = 0;
writersExecuting = 0;

void ReadersThread () {
 
     beginCriticalSection (1);    
     while (writersExecuting > 0) {
        endCriticalSection (1);
        sleep;
        beginCriticalSection (1);
     }
     currentReaders ++;
     endCriticalSection (1);

     /* reading */

     beginCriticalSection (1);     
     currentReaders --;
     endCriticalSection (1);
     wakeup;
}

void WritersThread () {

     beginCriticalSection (1);
     while ((writersExecuting > 0) || (currentReaders > 0)) {
         endCriticalSection (1);
         sleep;
	 beginCriticalSection (1);
     }
     writersExecuting ++;
     endCriticalSection (1);
     
     /* writing */
     beginCriticalSection(1);
     writersExecuting --;
     endCriticalSection(1);
     wakeup;
}