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Lecture

jan07ce.docx


Department
Computer Science
Course Code
CSC258H1
Professor
Steve Engels

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INTRODUCTION
Course Goals
o Understand the underlying architecture of computer systems
o Learn how to use thisarchitecture to store data and create
behaviour.
o Use the principles ofhardware design to createdigital logic
solutions to given problems.
Linking hardware an software
o Everything is 1’s and 0’s
o int:
(demical) 1234 (binary) 11000000111001
By default ints are 32 bits long, 231 positive values, 231
negative values
Total 232 integers
Singed Integers: range from 231 to 231-1
Unsinged Integers: range from 0 to 232-1
Different ranges for long, short, and byte
o if statements:
if value:
# what is value “True”?
False usually is 0, True usually is 1
If value is long and is 0.0 then it evaluates to false
Different data type, different requirements for T/F
o Power buttons
On & off are just binary singals
Eletrical signals
o The “ONE” and “ZERO” notations denotes high low voltage applied
between two points
ZERO: little to no voltage across the points
ONE: typically, a voltage difference of 5 volts
o for integers, read 32 signals, determine high/low as 1/0 to produce
a number
o Controlling Signals
typically change the voltage value that’s measured at a
particular point through use of switches and/or gates
o Combining singals
Switches are physical devices for manually closing a circuit to
control singals
Gates are semi-conductor devices that close a circuit
electrically
Assuming that certain signals can be turned on (ONE) or off
(ZERO), we need to have ways to combine these singals
together
every electronic device combines input signals to
create output signals
Ex. Ctrl Alt Del: if the Ctrl, Alt, and Delete buttons are
being pressed, restart the computer
Ex. Train signals: if three train tracks converge onto a
single track, only turn on the green light if a single
track has a train waiting
Logic gates
o Complex circuits aren’t drawn as switches
Diagrams with switches are horrible to read and draw
Only an abstraction for what really happens anyways
o Instead, logic gates are created to embody certain common digital
logic combinations
Represented by their truth tables
Certain gate functions conincide with typical Boolean
operators:
AND, OR, NOT, XOR
o AND gate i.e. A AND B
o OR gate i.e. A OR B
Ctrl
Alt
Del
Restart
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GO
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