~F8DATA STRUCTURE: TYPE BITS.

	Each node  has a  word reserved  for a  boolean vector of  36
values,  or bits. The  first eighteen bits  are called  the type bits
and are individually named as follows:

_____________________________________________________________________
 for	0	WESBIT		westward vector.
vectors	1	SOUBIT		southward vector.
 only	2	EASBIT		eastward vector.
	3	NORBIT		northward vector.
_____________________________________________________________________
	4	NFUSE		NTIME polygon fusion.
	5	NFISS		NTIME polygon fission.
 for 	6	NEXCT		NTIME polygon exact match.
polygons
 only 	7	PFUSE		PTIME polygon fusion.
	8	PFISS		PTIME polygon fission.
	9	PEXCT		PTIME polygon exact match.
_____________________________________________________________________
	10	HOLBIT		Hole polygon bit.
modify	11	ARCBIT		Arc vector bit.
_____________________________________________________________________
	12	SBIT		Shape node bit.
	13	VBIT		Vertex node bit.
	14	PBIT		Polygon node bit.
kind
	15	LBIT		Level node bit.
	16	IBIT		Image node bit.
	17	FBIT		Film node bit.
_____________________________________________________________________



	The first four  bits WESBIT, SOUBIT, EASBIT and  NORBIT apply
only  to vectors and indicate  the direction of the  vector. The next
six bits  NFUSE, NFISS, NEXCT,  PFUSE, PFISS,  PEXCT are  set by  the
polygon compare  routine to indicate  the kind of time  mating found;
where  N and  P mean  negative time  or postive time  linkage; fusion
means that the  given polygon  and another polygon  fuse to form  the
time polygon,  two into one; fission means  the given polygon splits,
one into two; and exact means  that the given polygon matchs one  for
one with its time polygon.

	The next  two bits HOLBIT  and ARCBIT  indicate distinguished
polygons  and vectors respectively.  Only one  of the last  six bits:
SBIT,  VBIT, PBIT,  LBIT, IBIT and  FBIT may be on  in a node.  These
bits indicate the node's type.
~I1973,800;F8- 11 -