#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <pthread.h>

// prototipo de funciones
void f_hilo1(void) ;
void f_hilo2(void) ;

char letra = 'a' ;

pthread_mutex_t m1 = PTHREAD_MUTEX_INITIALIZER ;
pthread_mutex_t m2 = PTHREAD_MUTEX_INITIALIZER ;

int main(int argc, char **argv) 
{
        pthread_mutex_lock(&m2);

	pthread_t hilo1;
	pthread_t hilo2;

	pthread_create(&hilo1,NULL,(void *)f_hilo1,NULL);
        pthread_create(&hilo2,NULL,(void *)f_hilo2,NULL);
		
	pthread_join(hilo1,NULL);
        pthread_join(hilo2,NULL);

        printf("\n");
	
        exit(0);
}

void f_hilo1(void) 
{  
  do
  {
        pthread_mutex_lock(&m1);
//        printf("%d\n",letra);
       printf("%c\n",letra);
 //      sleep(1) ;
        letra = letra - 31 ;
        pthread_mutex_unlock(&m2);        
  }while(letra < 'Z');
}

void f_hilo2(void) 
{  
 do  
 {
        pthread_mutex_lock(&m2);
    //    printf("%d\n",letra);
      printf("%c\n",letra);
        letra = letra + 33 ;   
        pthread_mutex_unlock(&m1);
  }while(letra < 'z');
}