text: #define	NALLOC	1024	/* minimum #units to request */
  
  /* morecore:  ask system for more memory */
  static Header *morecore(unsigned nu)
  {
  	char *cp, *sbrk(int);
  	Header *up;
  
  	if (nu < NALLOC)
  		nu = NALLOC;
  	cp = sbrk(nu * sizeof(Header));
  	if (cp == (char *) -1)	/* no space at all */
  		return NULL;
  	up = (Header *) cp;
  	up->s.size = nu;
  	free((void *)(up+1));
  	return freep;
  }
  