[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}]