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

Atanasoff-Berry Computer

    (ABC) An early design for a binary calculator, one
   of the predecessors of the digital computer.  The ABC was
   partially constructed between 1937 and 1942 by Dr. John
   Vincent Atanasoff and Clifford Berry at Iowa State College.
   As well as binary arithmetic, it incorporated regenerative
   memory, parallel processing, and separation of memory and
   computing functions.

   The electronic parts were mounted on a rotating drum, making
   it hybrid electronic/electromechanical.  It was designed to
   handle only a single type of mathematical problem and was not
   automated.  The results of a single calculation cycle had to
   be retrieved by a human operator, and fed back into the
   machine with all new instructions, to perform complex
   operations.  It lacked any serious form of logical control or
   conditional statements.

   Atanasoff's patent application was denied because he never
   have a completed, working product.  Ideas from the ABC were
   used in the design of ENIAC (1943-1946).

   (http://cs.iastate.edu/jva/jva-archive.shtml).

   (2003-09-28)