h=0.7
w=8.0
.gcolor white
box ht h wid w
.gcolor
move 

w=1.7

FS: arrow at last box .w + (0.4, 0)
DRI: arrow at last arrow .e + (w, 0)
DEV: arrow at last arrow .e + (w, 0)

.ps +4
TXTFS:  "filesystem" at 1/2 between FS.e  and DRI.w
TXTDRI: "driver"     at 1/2 between DRI.e and DEV.w
TXTDEV: "device"     at DEV.e + (w/2,0)
.ps

# subtexts
subtexth = 0.2
"(user interface," at TXTFS + (0, -subtexth)
"permissions,"   at Here + (0, -0.15)
"file to logical block addresses,"   at Here + (0, -0.15)
"some optimizations)" at Here + (0, -0.15)
"(logical to physical" at TXTDRI + (0, -subtexth)
"block addresses,"   at Here + (0, -0.15)
"some optimizations)" at Here + (0, -0.15)
"(actually stores data)" at TXTDEV + (0, -subtexth)

"files and" "directories" at 1/2 between FS.e and FS.w + (0, h)
"logical blocks" "ex: 0x10" at 1/2 between DRI.e and DRI.w + (0, h)
"physical blocks, AHCI commands" "ex: READ 0x2058 (LBA)" at 1/2 between DEV.e and DEV.w + (0, h)