[Unix: from IBM {JCL}] Equivalent to {cat} or {BLT}. Originally the
name of a Unix copy command with special options suitable for
block-oriented devices; it was often used in heavy-handed system
maintenance, as in "Let's dd the root partition onto a tape, then use
the boot PROM to load it back on to a new disk". The Unix dd(1) was
designed with a weird, distinctly non-Unixy keyword option syntax
reminiscent of IBM System/360 JCL (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(1) has been {deprecated} for a long time (though it has no
exact replacement). The term has been displaced by {BLT} or simple
English `copy'.
[glossary]
[Reference(s) to this entry by made by: {blit}{cat}{swab}]