Source : Free On-Line Dictionary of Computing

NAND
     
        Not AND.
     
        The {Boolean} function which is true unless both its arguments
        are true, the {logical complement} of {AND}:
     
        A NAND B = NOT (A AND B) = (NOT A) OR (NOT B)
     
        Its {truth table} is:
     
        	A | B | A NAND B
        	--+---+---------
        	F | F |    T
        	F | T |	   T
        	T | F |    T
        	T | T |    F
     
        NAND, like {NOR}, forms a complete set of {Boolean} functions
        on its own since it can be used to make NOT, AND, OR and any
        other Boolean function:
     
        NOT A = A NAND A
     
        A AND B = NOT (A NAND B)
     
        A OR B = (NOT A) NAND (NOT B)
     
        (1995-01-24)