The Free On-line Dictionary of Computing (30 December 2018):

D-type

   1.  A type of computer peripheral connector so named
   because one side is shorter (with one less pin) than the other
   giving a (squarish) "D" shape.  The connectors have two rows
   of pins (or holes).  Common types are 25-way (13+12 pins) and
   9-way (5+4 pins).  They are often used for serial lines,
   especially EIA-232.

   (1995-01-05)

   2. D-type flip-flop.