The Free On-line Dictionary of Computing (18 March 2015):

logical complementIn 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)