Page 67 - Computer science 868 Class 12
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2.1.2 AND Gate
AND gate requires at least two inputs and are called binary gates. It produces high output (1) only when all inputs are
high (1). In all other cases, low output (0) is produced. It is represented by a dot (.).
The symbol and truth table is shown below.
A B A.B A B C A.B.C
0 0 0 0 0 0 0
0 1 0 0 0 1 0
1 0 0 0 1 0 0
1 1 1 0 1 1 0
Truth table of two variables AND gate 1 0 0 0
1 0 1 0
1 1 0 0
1 1 1 1
Truth table of three variables AND gate
Multiple switches connected in series form an AND +
gate. From the circuit, we see that the lamp will L
glow if both switches A and B are closed. If any one -
is open, electricity will not flow and the lamp will Symbol of AND gate
remain off. Switching circuit diagram
of AND gate
2.1.3 OR Gate
OR gate is a binary gate. It produces high output (1) when any one input is high (1). Only when all inputs are low , 0
is produced as output. OR operation is represented by plus (+).
The symbol and truth table are shown below.
A B A+B A B C A+B+C
0 0 0 0 0 0 0
0 1 1 0 0 1 1
1 0 1 0 1 0 1
1 1 1 0 1 1 1
Truth table of two variables OR gate 1 0 0 1
1 0 1 1
1 1 0 1
1 1 1 1
Truth table of three variables AND gate
A
OR gate can be implemented with two switches B
A and B connected in parallel. If any one of the + L
switches or both are closed then electricity will -
flow through the circuit and the lamp will glow.
The lamp will remain switched off when both Symbol of OR gate
switches are open. Switching circuit of
OR gate
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Computer Hardware 65

