CPSC 121
Lecture 2
January 7, 2009
Menu January 7, 2009
Topics:
Propositional Logic
Logic Gates
Reading:
Today:
Epp 1.1, 1.4
January 9: Epp 1.2
Next week:Epp 1.5, 1.3
Handouts:
Lab 0 part 1
(repeated)
Questionnaire
(repeated)
Course Outline
(online only)
Reminders:
Online Quiz 2 deadline 9:00pm January 8
Online/static Quiz 1 (mark has been waived)
Labs and tutorials begin week of January 12
www:
http://www.ugrad.cs.ubc.ca/~cs121/
WebCT Vista:
http://www.vista.ubc.ca
The ﬁrst lecture introduced the switch as the fundamental physical structure upon which digital computation is built.
The bit (0/1) is the corresponding mathematical abstraction. Switches are concrete. Two things about switches to
remember from the ﬁrst lecture: 1) with switches we can compute; and 2) switch technology is an area where it is
reasonable to expect both continuous and revolutionary advancement in the years ahead.
The six examples included at the end of the last lecture are intended to explore what it means to “prove” something
mathematically.
Here’s a summary. Spend a moment or two to think about which of the propositions are true, which of them are false
and (more importantly as motivation for today) how we might know for sure which are true and which are false.
Example Propositions (Summary)
Proposition 1:
2 + 3 = 5
Proposition 2:
5 + 3
×
5 = 20
Proposition 3:
Intel’s original Pentium processor chip performed ﬂoating point division properly
Proposition 4: (Goldbach)
Every positive even integer greater than
2
can be written as the sum of two primes
Proposition 5:
Let
n
be a natural number. Then the natural number
p
(
n
) =
n
2
+
n
+ 41
is prime
Proposition 6: (Euler)
There are no positive integers
a
,
b
,
c
,
d
, such that
a
4
+
b
4
+
c
4
=
d
4
Propositional Logic
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View Full DocumentPropositional Logic
A proposition is a statement that is true or false (but not both)
We combine propositions together to create new propositions, called compound propositions
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 Spring '08
 BELLEVILLE
 Logic, Logical connective, truth values, T. Column

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