Lesson 2. Boolean Algebra
Lesson Objective
- Be familiar with the use of Boolean identities and De Morgan’s laws to manipulate and simplify Boolean expressions.
- Write a Boolean expression for a given logic gate circuit, and vice versa.
- Use the following rules to derive or simplify statements in Boolean algebra:
- De Morgan’s Laws
- Distribution
- Association
- Commutation
- Absorption
- Double negation
Lesson Notes
Boolean Algebra?
Boolean algebra is a mathematical system for working with logical values (true and false) and the operations that combine them. It's a formal method used to manipulate and simplify logical statements, which is very important in computer science and digital circuit design. Rules for simplifying Boolean expressions, like absorption (X ⋀ (X ⋁ Y) = X) and general (X ⋁ ¬X = 1), help us reduce complex expressions to simpler forms that are easier to understand and use.
De Morgan's laws are a key tool for handling negations of combined terms. Specifically, they state that the opposite of "A or B" is the same as "not A and not B," and the opposite of "A and B" is the same as "not A or not B." These laws are crucial for simplifying and changing Boolean expressions, which often results in more efficient ways of implementing them.
Rules
General Rules
- X ⋀ 0 = 0
- X ⋀ 1 = X
- X ⋀ X = X
- X ⋀ ¬X = 0
- X ⋁ 0 = X
- X ⋁ 1 = 1
- X ⋁ X = X
- X ⋁ ¬X = 1
- ¬¬X = X
Commutative Rules
- X ⋀ Y = Y ⋀ X
- X ⋁ Y = Y ⋁ X
Associative Rules
- X ⋀ (Y ⋀ Z) = (X ⋀ Y) ⋀ Z
- X ⋁ (Y ⋁ Z) = (X ⋁ Y) ⋁ Z
Distributive Rules
- X ⋀ (Y ⋁ Z) = X ⋀ Y ⋁ X ⋀ Z
- (X ⋁ Y) ⋀ (W ⋁ Z) = X ⋀ W ⋁ X ⋀ Z ⋁ Y ⋀ W ⋁ Y ⋀ Z
Absorption Rules
- X ⋀ (X ⋁ Y) = X
- X ⋁ (X ⋀ Y) = X