A
Unix copy command with special options suitable for
block-oriented devices; it was often used in heavy-handed
onto a tape, then use the
boot PROM to load it back on to a
new disk".
The Unix "dd" was designed with a weird, distinctly non-Unixy
(which had an elaborate DD "Dataset Definition" specification
for I/O devices); though the command filled a need, the
interface design was clearly a prank.
The jargon usage is now very rare outside Unix sites and now
nearly obsolete even there, as "dd" has been
deprecated for
a long time (though it has no exact replacement). The term
has been displaced by
BLT or simple English "copy".
(1995-02-03)