#include <stdio.h>#include <stdlib.h>#include <pthread.h>void *print_message_function( void *ptr );pthread_mutex_t mutex1 = PTHREAD_MUTEX_INITIALIZER;int  counter = 0;main(){     pthread_t thread1, thread2;     char *message1 = "Thread 1";     char *message2 = "Thread 2";     int  iret1, iret2;        /* Create independent threads each of which will execute function */     iret1 = pthread_create( &thread1, NULL, print_message_function,	  	 	    (void*) message1);     iret2 = pthread_create( &thread2, NULL, print_message_function, 			    (void*) message2);     /* Wait till threads are complete before main continues. Unless we  */     /* wait we run the risk of executing an exit which will terminate   */     /* the process and all threads before the threads have completed.   */     pthread_join( thread1, NULL);     pthread_join( thread2, NULL);      printf("Thread 1 returns: %d\n",iret1);     printf("Thread 2 returns: %d\n",iret2);     exit(0);}void *print_message_function( void *ptr ){     char *message;     message = (char *) ptr;     pthread_mutex_lock( &mutex1 );     counter++;     printf("Counter value: %d,Message: %s\n",counter,message);	     pthread_mutex_unlock( &mutex1 );}