Boolean AlgebraElectrical Engineering

LAWS OF BOOLEAN ALGEBRA

The Boolean algebra is governed by certain well developed rules and laws.

Commutative Laws

  • The commutative law allows change in position of AND or OR variables. There are two commutative laws.
    (i) A + B = B + A
    Thus, the order in which the variables are ORed is immaterial.
    (ii) A ⋅ B = B ⋅ A
    Thus, the order in which the variables are ANDed is immaterial.
  • This law can be extended to any number of variables.

Associative Laws

  • The associative law allows grouping of variables. There are two associative laws
    (i) (A + B) + C = A + (B + C)
    Thus, the way the variables are grouped and ORed is immaterial.
    (ii) (A ⋅ B) ⋅ C = A ⋅ (B ⋅ C)
    Thus, the way the variables are grouped and ANDed is immaterial.
  • This law can be extended to any number of variables.

Distributive Laws

  • The distributive law allows factoring or multiplying out of expressions. There are two distributive
    laws.
    (i) A(B + C) = AB + AC
    (ii) A + BC = (A + B) (A + C)
  • This law is applicable for single variable as well as a combination of variables.

Idempotent Laws

  • Idempotent means the same value. There are two Idempotent laws
    (i) A ⋅ A = A
    i.e., ANDing of a variable with itself is equal to that variable only.
    (ii) A + A = A
    i.e., ORing of a variable with itself is equal to that variable only.

Absorption Laws

  • There are two absorption laws
    (i) A + AB = A(1 + B) = A (ii)A (A + B) = A

Involutory Law

  • This law states that, for any variable ‘A’
    A = (A′)′ = A

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