~F88. EMPTY NODE FORMAT.

	_____________________________________________ 
	word |                   |        CCW        |
	  0  |       ---         |       avail       | 1
	_____|___________________|___________________|
	word |                   |                   |
	  1  |       ---         |       ---         | 0
	_____|___________________|___________________|
	word |       type        |       reloc       |
	  2  |                   |      00 0000      |
	_____|___________________|___________________|
	word |                   |                   |
	  3  |       ---         |       ---         | 0
	_____|___________________|___________________|
	word |                   |                   |
	  4  |       ---         |       ---         | 0
	_____|___________________|___________________|
	word |                   |                   |
	  5  |       ---         |       ---         | 0
	_____|___________________|___________________|
	word |                   |                   |
	  6  |       ---         |       ---         | 0
	_____|___________________|___________________|


	The  list of  empty  nodes  is  maintained in  the  CCW  link
postion; the last  empty node contains a zero or NIL link. At present
all the other words of an empty node are zero.


FIGURE SHOWING RASTER STRUCTURE._____________________________________

				↑
				↑
			       NORTH
	 grid point R,C			 R,C+1
			o____HSEG______o
			|
			|
	         	|
       ←←←WEST        VSEG   PIXEL(R,C)		EAST→→→
			|
			|
			|
		        o     SOUTH
 		  R+1,C		↓
				↓
_____________________________________________________________________
~I1973,800;F8- 19 -