Page 83 - Computer Science V2.0 Class 11

A B A ● B
0 0 0
0 1 0
1 0 0
1 1 1

Table 3.1: AND operator using operand values 0 and 1
If we use true and false in place of 1 and 0, the above table would appear as shown in Table 3.2.

A B A ● B
false false false
false true false
true false false
true true true

Table 3.2: AND operator using operands true and false
A table that describes the result of applying an operator (such as AND) on each combination of values of the variables
is called truth table (see Table 3.1 and Table 3.2). The electric circuit shown in Fig 3.1 may be used to implement the
AND operator.

Voltage ∼

A AND B

A B
Fig 3.1: Electric circuit for AND operator

Fig 3.1 shows two switches in series connected to a voltage source and a bulb. The two switches denote variables A
and B, and the bulb's output denotes A ● B. The OFF position of the switch denotes 0, and the ON position denotes
1. Similarly, the OFF position of the bulb denotes 0, and the ON position denotes 1. The bulb will be ON if and only if
both switches are in the ON position.

3.2.2 OR Operator

The OR operator (often called OR gate) is denoted by writing OR or +. For a pair of variables, A and B, A OR B yields 1
if either A = 1 or B = 1 and yields 0 if A = 0 and B = 0 (see Table 3.3). The electric circuit shown in Fig 3.2 implements
the OR operator.

A B A OR B

0 0 0
0 1 1
1 0 1
1 1 1

Table 3.3: OR operator using operand values 0 and 1

Boolean Logic 69