.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) arrow right line up boxht/2 line right boxwid/2 move down boxht line left boxwid/2 then up boxht/2 move right boxwid/2 arrow "device" "out" move down boxht arrow left "device" "in" move down boxht/2 line left boxwid/2 then up boxht move down boxht/2 arrow left move up boxht/2 line down boxht then left boxwid/2 move up boxht/2 arrow left "user" "read" .PE .sp .5 .ce Figure 1. Configuration after device open. .sp .KE