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1
Hardware:
How Computer Programs Run
on Physical Machines
The hardware level of a computer
•
Binary numbers
are
used to encode all forms of
data, such as numbers and letters
•
Electric circuits
process and store binary data
• Simple
gates
can be combined to build circuits
for any computation
•
Boolean logic
is a useful abstraction of electric
circuits
These are the topics we’ll be discussing this week
The binary number system
•
Bi
nary digi
ts
(“bits”) have values 0 and 1
• The position of each digit determines its value
for example, the binary number 101011 equals:
1x2
5
+ 0x2
4
+ 1x2
3
+ 0x2
2
+ 1x2
1
+ 1x2
0
=
32
+
0
+
8
+
0
+
2
+
1
=
43
10
• note the similarity with decimal numbers:
572
10
= 5x10
2
+
7x10
1
+ 2x10
0
Why use binary, not decimal or .
..?
• At the hardware level, data is manipulated
and stored with electrical circuits
• So, data must correspond to electronic
quantities, such as voltage and current
• A “decimal computer” could be built using an
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 Spring '08
 J.Parker

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