#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;
}