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

digital electronics

    The implementation of two-valued logic using
   electronic logic gates such as and gates, or gates and
   flip-flops.  In such circuits the logical values true and
   false are represented by two different voltages, e.g. 0V for
   false and +5V for true.  Similarly, numbers are normally
   represented in binary using two different voltages to
   represented zero and one.

   Digital electronics contrasts with analogue electronics
   which represents continuously varying quantities like sound
   pressure using continuously varying voltages.

   Digital electronics is the foundation of modern computers and
   digital communications.  Massively complex digital logic
   circuits with millions of gates can now be built onto a single
   integrated circuit such as a microprocessor and these
   circuits can perform millions of operations per second.

   (2006-01-14)