In the truth table case by case the function behaviour is specified. The truth table has two parts: input and output. The truth table from the previous logic function S= A·B will be affirmative in the case that the two logic variables that compose it are also affirmative.

Let's check the values of the two variables in each case: 

Logic Variable	Logic Variable
A	B
0	0
1	1

 

Combined logic variables
A	B
0	0
0	1
1	0
1	1

 

Logic function Truth table S = A·B
A	B	S
0	0	0
0	1	0
1	0	0
1	1	1

 

The number of rows that we can obtain in a truth table depends on the number of independent input variables to take into account. In the case of being tree independent variables, 8 would be the results. The number of rows in the truth table can be calculated through the equation 2ⁿ, where n is the number of logic input variables.