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Adder
An electronic
circuit that performs an
addition operation on
binary values
Half adder
A circuit
that computes the sum of
two bits and produces
the appropriate carry bit
102
Chapter 4
Gates and Circuits
These
properties
are
consistent
with
our
understanding
of
gate
processing, and with the truth table and logic diagram representations.
For instance, the commutative property, in plain English, says that the
order of the input signals doesn’t matter, which is true. (Verify it using
the truth tables of individual gates.) The complement property says that
if we put a signal and its inverse through an AND gate, we are guaran
teed to get 0, but if we put a signal and its inverse through an OR gate,
we are guaranteed to get 1.
There is one very famous—and useful—theorem in Boolean algebra called
DeMorgan’s law
. This law states that the NOT operator applied to the AND
of two variables is equal to the NOT applied to each of the two variables with
an OR between. That is, inverting the output of an
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 Fall '10
 MARIANAKANT

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