( i ) NAND Gate When output of AND gate is applied as input to a NOT gate , then it is called a NAND gate .
Boolean expression Y = A * B ( Y equals negated of A AND B )
( ii ) NOR Gate When output of OR gate is applied as input to a NOT gate , then it is called a NOR gate .
Boolean expression Y = A + B ( Y equals negated of A OR B )
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The Boolean expression obey commutative law associative law as well as distributive law .
1 . A + B = B + A 2 . A · B = B · A 3 . A + ( B + C ) = ( A + B ) + C
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Demorgan ’ s theorems 1 . A + B = A * B
2 . A * B = A + B