text: #ifndef POSIX_THREAD
  #define POSIX_THREAD
  
  #define NULL 0
  #define PGSIZE (4096)
  
  typedef struct{
    int pid;
  } pthread_t;
  
  typedef struct{
    int id;
  } pthread_mutex_t;;
  
  int pthread_create(pthread_t *thread, void* (*func) (void*), void *arg);
  int pthread_join(pthread_t thread, void **retVal);
  int pthread_exit(void *retVal);
  
  int pthread_mutex_init(pthread_mutex_t *mutex);
  int pthread_mutex_lock(pthread_mutex_t *mutext);
  int pthread_mutex_unlock(pthread_mutex_t *mutex);
  int pthread_mutex_destroy(pthread_mutex_t *mutex);
  
  #endif
  