dd

( /dee·dee/, vt.)

   [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}]