figure1.pic

早期freebsd实现

.PS 5.9i
## figure 1
C1:	ellipse "\UA/"
B1:	box "\MTA/" with .n at (C1.s.x, C1.s.y-3*lineht)
B8:	box "\MTA/" with .w at (B1.e.x+linewid, B1.e.y)
B2:	box invis "$\ldots$" with .w at (B8.e.x+linewid, B1.e.y)
B9:	box invis "$\ldots$" with .w at (B2.e.x+linewid, B1.e.y)
B3:	box "\MTA/" with .w at (B9.e.x+linewid, B1.e.y)
C2:	ellipse "\UA/" with .s at (B3.n.x, C1.s.y)
##
	arrow from C1.s to B1.n
	arrow from B1.e to B8.w
	arrow from B8.e to B2.w
	arrow from B2.e to B9.w
	arrow from B9.e to B3.w
	arrow from B3.n to C2.s
##
B4:	box width B3.e.x+linewid/3-(B1.w.x-linewid/3) \
	    height 3*boxht \
	    with .c at B2.c
	move to (B4.n.x, B4.n.y-lineht/2); "\MTS/"
##
	line dashed "POSTING" "" \
		from (B4.w.x-linewid, B4.n.y+lineht/2) \
		to   (C1.s.x, B4.n.y+lineht/2)
	line dashed "RECEIPT" "" \
		from (B4.e.x+linewid, B4.n.y+lineht/2) \
		to   (C2.s.x, B4.n.y+lineht/2)
	move to ((B2.e.x+B9.w.x)/2, B2.s.y); "RELAYING"
##
.PE