V10/vol2/ipc/fig3

.KF
.PS
boxht = boxht/1.5
arrow "user" "write"
move up boxht/2
line right boxwid/2 then down boxht then left boxwid/2
move by (boxwid/2, boxht/2)
spline -> right linewid then down boxht right linewid then right linewid
move up boxht
line up boxht/2
line right boxwid/2 
move down boxht
line left boxwid/2 then up boxht/2
move right boxwid/2
arrow <- "user" "write"
move down boxht left linewid
arrow -> right "user" "read"
move down boxht/2 left linewid
line left boxwid/2 then up boxht
move up boxht/2
spline -> left linewid then down boxht left linewid then left linewid
move up boxht/2
line down boxht then left boxwid/2
move up boxht/2
arrow left "user" "read"
.PE
.sp .5
.ce
Figure 3.  A pipe.
.sp
.KE