CS 211: Computer Organization › Lesson 2 of 10

Boolean Algebra & Logic Minimization

Lesson 2 · OKSTEM College · AS Computer Science

Boolean Algebra & Logic Minimization

Study Boolean Algebra & Logic Minimization — complete the practice problems in your notebook.

Interactive Lab

Knowledge Check

Which Boolean identity is De Morgan's first theorem?

Correct — De Morgan's first law.
That is De Morgan's second law, not the first.
That is the distributive law.
That is the complement law (tautology).
📖 Quick Recap

De Morgan's laws come in a pair: NOT(A∧B) = ¬A∨¬B, and NOT(A∨B) = ¬A∧¬B. The first is about negating AND.

📖 Quick Recap

The distributive law expands AND over OR. De Morgan's laws relate negation of AND/OR to OR/AND of negations.

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A ∨ ¬A = 1 is the complement/tautology law. De Morgan's laws involve negating compound expressions.

A Karnaugh map is used to:

K-maps are for logic minimization, not memory design.
Correct — adjacent 1-cells can be grouped to eliminate variables.
BCD encoding is a separate technique.
Floating-point uses IEEE 754 format, not K-maps.
📖 Quick Recap

K-maps minimize Boolean expressions. RAM design involves addressing, decoders, and latches — different topic.

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BCD (Binary-Coded Decimal) represents each decimal digit in 4 bits. K-maps minimize logic functions.

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IEEE 754 defines sign/exponent/mantissa fields. K-maps are for combinational logic optimization.

The Boolean expression A·(A+B) simplifies to:

Partial simplification — apply absorption: A·(A+B) = A.
Incorrect. Try A=1,B=0: A·(A+B)=1·1=1, but A·B=0. They differ.
Correct — absorption law: A·(A+B) = A.
Not always. When A=0 the expression is 0, not 1.
📖 Quick Recap

Absorption law: A·(A+B) = A. Think: if A is 0 the whole expression is 0; if A is 1 the whole expression is 1. Result = A.

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Test with A=1,B=0: original = 1·(1+0)=1·1=1. A·B=1·0=0. Not equal. Use the absorption law: A·(A+B)=A.

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If A=0: 0·(0+B)=0. So the result is not always 1. Correct simplification is A.

In sum-of-products (SOP) form, each term is:

SOP terms are products (ANDs) of literals; they are then OR'd together.
Correct — each term ANDs literals; the SOP expression ORs those terms.
XOR is a separate operation, not the structure of SOP.
NAND is a universal gate, but not the definition of an SOP term.
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SOP = Σ(products). Each minterm is an AND of literals. The minterms are then summed (OR'd).

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SOP uses AND within terms and OR between terms. XOR (⊕) is its own operation.

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NAND = NOT AND. SOP terms are standard AND of literals without additional inversion.

Which law allows replacing A + A·B with A?

Idempotent: A+A=A. Different from what's needed here.
Correct — A + A·B = A by absorption.
Commutativity just swaps operand order: A+B=B+A.
Associativity regroups terms: (A+B)+C = A+(B+C).
📖 Quick Recap

Idempotent: A+A=A or A·A=A. The expression A+A·B uses the absorption law: A+A·B=A.

📖 Quick Recap

Commutativity reorders operands. Absorption removes a redundant term: A+AB=A.

📖 Quick Recap

Associativity changes grouping, not simplification. Absorption: A+AB=A.

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