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

logical complement

    In Boolean algebra, the logical complement or
   negation of a Boolean value is the opposite value, given by
   the following truth table:

   	A | -A
   	--+---
   	T | F
   	F | T

   -A is also written as A with a bar over it or with a small
   vertical line hanging from the right-hand end of the "-"
   (LaTeX \neg) or as A'.  In the C programming language, it
   is !A and in digital circuit design, /A.

   (1995-01-24)