29.
31. The truth table provides a simple means for testing the
a. 23=8
logical equivalence of two or more Boolean expressions. To
test the logical equivalence of two expressions, construct a
b. 2 =4
2
truth table for both expressions. If both expressions have the
c. 23 = 8
same truth value for each case (row) in the truth table, the
expressions are equivalent and can be substituted for each
d. 22 = 4
other. For example: Prove that A+AB=A.
e. 24 =16
A
B
AB
A+AB
A+AB=A
0
0
0
0
1
0
1
0
0
1
1
0
0
1
1
1
1
1
1
1
The third column in the truth table above represents the
30
logical product (AB) for two variables. The fourth column
INPUTS
OUTPUTS
represents the logical product and sum (A+AB) of two
C
D SUM CARRY
0
0
0
0
variables. A "1" is placed in this column when either the A
0
1
1
0
1
0
1
0
column or the AB column or both have a truth value of 1.
1
1
0
1
The fifth column is a comparison of the first column (A) and
the fourth column (A+AB). A 1 is placed in this column
whenever the truth value of the two columns is the same;
i.e., both 0 or both 1.
IT 0346
1-20
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