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04 - Boolean Algebra and Circuits

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Introduction to Computer Systems (Comp 273)

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Boolean Algebra and Circuits

Overview

á Truth Tables

á Boolean Functions

á Logic Gates

á Combinatorial Circuits

á Appendix C

Boolean Operations

á Consider binary variables, A, B

± Possible values are 0 (FALSE) and 1 (TRUE)

á Different possible inputs with n operands = 2n

± 2 binary operands: 2 2 = 4 different possible inputs

± 4 binary operands: 2 4 = 16 different possible inputs

A A B

0

1

A B C

Boolean Operations

á Consider binary variables, A, B

± Possible values are 0 (FALSE) and 1 (TRUE)

á Different possible inputs with n operands = 2n

± 2 binary operands: 2 2 = 4 different possible inputs

± 4 binary operands: 2 4 = 16 different possible inputs

A B

0 0

0 1

1 0

1 1

A

0

1

A B C

Ï 2 Ï 2 Ï 2

Ï 2 Ï 2 Ì 2

Ï 2 Ì 2 Ï 2

Ï 2 Ì 2 Ì 2

Ì 2 Ï 2 2 Ï

Ì 2 Ï 2 Ì 2

Ì 2 Ì 2 Ï 2

Ì 2 Ì 2 Ì 2

Boolean Operations

á A Boolean Function is an algebraic expression consisting of

binary variables and the logic operation symbols

á Any Boolean function can be written in terms

of AND, OR, and NOT

á Truth table defines all possible outcomes A B | A + B

0 0 0 0

0 1 0 1

1 0 0 1

1 1 1 1

Boolean Algebra

á Rules capture logical reasoning

á Allow for manipulation of expressions

Are two boolean functions equivalent?ent?

Prove it, or find values to show that they are not!

||[=||[=||[ [

|~|[=|[

Boolean Algebra

Derive Boolean Expression

á Consider a logic function with three inputs, A , B , and C , and

three outputs, D , E , and F.

± D is true if at least one input is true

± E is true if exactly two inputs are true

± F is true only if all three inputs are true

á Find the Boolean expression for D, E, and F.

Derive Boolean Expression

Find the truth table! D is true if at least one input is true

A B C D

Ï 2 Ï 2 Ï 2

Ï 2 Ï 2 Ì 2

Ï 2 Ì 2 Ï 2

Ï 2 Ì 2 Ì 2

Ì 2 Ï2 2Ï

Ì 2 Ï 2 Ì 2

Ì 2 Ì 2 Ï 2

Ì 2 Ì 2 Ì 2

Derive Boolean Expression

Find the truth table! F is true only if all three inputs are true

A B C D E F

Ï 2 Ï 2 Ï 2 0 0

Ï 2 Ï 2 Ì 2 1 0

Ï 2 Ì 2 Ï 2 1 0

Ï 2 Ì 2 Ì 2 1 1

Ì 2 Ï2 2Ï 1 0

Ì 2 Ï 2 Ì 2 1 1

Ì 2 Ì 2 Ï 2 1 1

Ì 2 Ì 2 Ì 2 1 0

Derive Boolean Expression

What are the Boolean expressions for outputs D, E, and F?

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04 - Boolean Algebra and Circuits

Course: Introduction to Computer Systems (Comp 273)

80 Documents
Students shared 80 documents in this course

University: McGill University

Was this document helpful?
Boolean Algebra and Circuits