.PS
## figure 21
C1:	circle rad 1.75i
##
B1:	box with .n at C1.n invis "The" "Directory"
##
C2:	circle with .w at C1.w rad .4i		"\xx DSA"
C3:	circle with .e at C1.e rad .4i		"\xx DSA"
##
C4:	circle at (C1.w.x - (C1.c.x - C1.w.x), C2.w.y) \
					rad .4i "\xx DUA"
##
B2:	box at C2.w shaded	height .06i width .18i
B3:	box at C2.e shaded	height .06i width .18i
B4:	box at C3.w shaded	height .06i width .18i
B5:	box at C3.e shaded	height .06i width .18i
##
B6:	box at C4.e shaded	height .06i width .18i
##
L1:	line from B6.e to B2.w "DAP" above
L2:	line from B3.w to B4.e "DSP" above
##
.PE