CPSC 121
Lecture 6
January 16, 2009
Menu January 16, 2009
Topics:
Example: 7 Segment LED Display (cont’d)
Canonical Forms
— Disjunctive Normal Form (DNF)
— Conjunctive Normal Form (CNF)
Reading:
Today:
Epp 1.3
Next week: Epp 2.1, 2.3
Reminders:
Assignment 1 due Friday, January 30, 17:00
READ
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WebCT Vista:
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www:
http://www.ugrad.cs.ubc.ca/~cs121/
Disjunctive Normal Form (DNF)
A canonical representation for a logical formula,
P
, as a disjunction of
clauses,
Q
i
,
i
= 1
,
2
,...,m
, each of which is
itself a conjunction. That is,
P
=
Q
1
∨
Q
2
∨
...
∨
Q
m
where each clause,
Q
i
, is of the form
q
1
∧
q
2
∧
...
∧
q
n
and where each
q
i
is a
literal
(i.e., a propositional variable or the negation of a propositional variable)
Disjunctive Normal Form (DNF)
is useful to determine a logical formula corresponding to a given truth table (based
on rows in the table that are
T
)
Example 1:
Consider the following truth table:
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 Spring '08
 BELLEVILLE
 Logic, Logical connective, Conjunctive normal form, disjunctive normal form

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