ELEC1601
Introduction to Computer Systems
Outline:
Introduction to course
Course admin
Computers at a high‐level (course overview)
Lab intro
Encoding numbers
Introduction to Computer
Systems
Why are you here
Why are you here
You have no choice…
It is a core unit
Why are you here
You want to understand how computers work
Not how to use MS Word/send email…
Why are you here
You want to understand how computers work
Not how to use MS Word/send email…
What is inside a computer
How could you design your own computer
Make the best better
How does a computer ‘talk’ to other devices
Hardware vs software
How do you use a computer efficiently
What is involved in understanding computers
You may already have your favourite programming language
You are talking to them
But circuit only understands 0’s and 1’s
We will learn how to bridge the gap
Why do people like this course
Why do people like this course
You want to understand how computers work
Why do people like this course
You want to understand how computers work
Fun
Practical
Fun/Practical
Learn how to control a real‐chip…ish
We use an Arduino
You should build skills and methodologies to talk to any computer
Fun/Practical (e.g. lab1)
Let’s talk about computer
systems
What is a computer system
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What is a computer system
Something you communicate through keyboard/mouse/touchscreen
Supporter of apps
Something that does mass arithmetic instructions
Something that integrates inputs and computation
A collection of digital logic that can execute machine instructions
What is a computer system
Something you communicate through keyboard/mouse/touchscreen
Supporter of apps
Something that does mass arithmetic instructions
Something that integrates inputs and computation
A collection of digital logic that can execute machine instructions
An electronic brain
Typical structure of a computer system
What is a program
Written in a programming language
Meaning defined by language
Program to execution
Sequence of steps
Assembly language
Human readable machine language
Map directly to binary digits
Can you program in assembly language
Yes…
You can write extremely efficient code
But…You need to understand the processor in detail
You may not be smarter than a compiler…
Program execution
Yes…
You can write extremely efficient code
But…You need to understand the processor in detail
You may not be smarter than a compiler…
Abstraction
Are all computers the same
Course Details
Course scenario
Lectures
Under the hood ‐ Understand circuit/architecture
Lab
Designing a system ‐ Program it bottom up
Learning Objectives
Content should always be linked to these objectives
We are here to help you achieve
Additional Learning Objectives
We want to help you to learn how to learn
What are your learning strategies
How did you study for your HSC/VCE/IBAC/A‐levels
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Strategies for sophisticated learners
You are going to run a marathon
Strategies for sophisticated learners
Example learning strategy
Lectures
Attend
Tutorials
Attend
Do exercises as instructed by tutor
Labs
Attend
Complete as much as possible during lab session
Write lab report afterwards
Exam
Study during STUVAC
Make sure you complete all past lecture quizzes
Extra last minute study before relevant exam
Go to any ‘exam consultation sessions’ organised by lecturer
Strategies for sophisticated learners
We want you to experience new options that can potentially help you
to learn better.
Dual‐process theories of reasoning
Brain processes in two ways
System 1:
Intuitive/instantaneous
Walk down street
What is 2+2
Effortless
System 2:
Invoked when system 1 fails to solve problem
Tries to create a rational answer
You are not learning when you are using system 1
A better learning strategy
Lectures
Prepare for lectures
Not at the last moment
Distributed practice better
Attend
Participate diligently/actively
Be willing to make mistakes
Tutorials
Prepare for lectures
Attend
Do exercises as instructed by tutor
Participate diligently/actively
Be willing to make mistakes
Be willing to get ahead/go beyond/ask tutor more questions
A better learning strategy
Labs
Prepare for lab in advance
Attend
Complete as much as possible during lab session
Build your team
Use the demonstrators
Write lab report afterwards
SPEAK UP EARLY ABOUT ANY ISSUES
A better learning strategy
Exam
Study throughout semester
Have a study plan for exam period starting during STUVAC
Make sure you complete all past lecture quizzes
DO NOT DEPEND ON THIS
Extra last minute study before relevant exam
Go to any ‘exam consultation sessions’ organised by lecturer
Only if they can help you
Use your friends
Use the discussion forum
Learning strategies
Learning strategies
We want you to prepare before a lecture.
Really Why
Learning strategies
We want you to prepare before a lecture.
Really Why
So you can work in lecture
Active participation
Talk to partners.
Lectures only contain a subset of the information in Canvas.
Learning strategies
Tutorials should follow lectures
You are introduced to ideas, but build on it in tutorials.
Harder questions
More help
Learning strategies
Labs arguably separate
More practical
But it should all come together at the end
Bureaucratic stuff
Your life for this course
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How do I pass
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How do I pass
Lab Completion
Marked as a group.
We will test anyone at random. You have the responsibility to teach your
peers
Lab reports (weeks 3‐6)
Submit before start of next lab
Each group member will take a turn
How do I pass
Midterm
Give you an idea how things work/how you are tracking
Project
Changing focus to quality
Exam
Hurdle task. Can’t ride on your peers
How this course is structured/What you need
to do each week
Know what week you are in
Do not get behind
Do not do the wrong tasks
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Plagiarism
Taken very seriously at university
Edstem
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Ask questions
Answer other questions
Does not matter
if your answers are incorrect
Discussion will improve them
Labs
Groups of 5. CC/RE same
If you want to create a team in advance OK
When you join a lab, change your name to be group1_<>
Simulation based
Zoom breakout rooms
Discord chat encouraged
Screen sharing encouraged
Remote control encouraged
Codeshare encouraged
Mini‐demo
Encoding Information
Why do computers need to encode
information
Why do computers need to encode
information
Because they can only deal with 0’s and 1’s
What do we mean by encoding information
for computers
What do we mean by encoding information
for computers
Numbers
(binary)
What do we mean by encoding information
for computers
Numbers
(binary)
Colours
Red/green/blue
Machine Code
What do we mean by encoding information
for computers
Anything that you possibly want to do with a computer
What do we mean by encoding information
for computers
Literally everything…
Start with numbers…
Why
Computers very good at arithmetic
Computers do a lot of arithmetic
Start with natural numbers
What are they
How do we count numbers in base 10
How do we count numbers in binary
Same way, but max of 2
What do numbers in base 10 mean
Consider the number 1429
How do we break it down
What does a binary number mean
Consider the number 111010 mean
How do we break it down
How do we convert numbers between bases
Convert 382710 to binary
Why Octal/Hexadecimal
How do you think this monitor is encoded
Why Octal/Hexadecimal
Make binary more human readable
Conversion (from binary) is easy
First exercise from worksheet
Useful properties of base 10
Is 1345 a multiple of 10 Is it a multiple of 100
Is 13450 a multiple of 10 Is it a multiple of 100
Is 10400 a multiple of 10 Is it a multiple of 100
Is this hard
Useful properties of base 10
How do you multiply 1274 by 10
How do you multiply 1830 by 100
Is this hard
Useful properties of base 10
How do you divide 10400 by 10
How do you divide 10400 by 100
Is this hard
Useful properties of base 10
Is 1345 a multiple of 7 Is it a multiple of 77
Is 13450 a multiple of 70 Is it a multiple of 777
Is 10400 a multiple of 70 Is it a multiple of 777
How do you multiply 1274 by 7
How do you multiply 1830 by 77
How do you divide 10400 by 77
How do you divide 10400 by 777
Is this hard
Useful properties of base 2
Is 101100 a multiple of 2 Is it a multiple of 4
How do you multiply 1010010 by 2
How do you multiply 1011110 by 4
How do you divide 10101010 by 2
How do you divide 10111100 by 4
Is this hard
Useful properties of base 8, base 16
Worksheet exercise 2
Couple of bonus questions
What is 10016 ‐1
How many different numbers can you
represent
10 digits
10 octal values
10 hex values
10 bits
Encoding integers
What is the difference between the set of integers and set of natural
numbers
Encoding integers
What is the difference between the set of integers and set of natural
numbers
Sign‐magnitude: the easiest way to represent negative numbers
Add a sign bit
Encoding integers
What is the difference between the set of integers and set of natural
numbers
Sign‐magnitude: the easiest way to represent negative numbers
Add a sign bit
Is this a good representation
How do we add sign‐magnitude numbers
How do we add positive numbers
How do we add 1503+1729
How do we add positive binary numbers
How do we add 1001+1011
How do we add sign‐magnitude numbers
Suppose we have two binary numbers in sign‐magnitude
representation:
A+B (A+ve, B+ve)
A+B (A+ve, B‐ve)
A+B (A‐ve, B‐ve)
One’s complement
Invert all bits
Simpler addition
Two’s complement
Easy to compute
Invert all bits and add 1
Has a direct understanding
Simpler addition still
Worksheet Q2
Why Floating‐point
Encoding Real Numbers
Do we need floating‐point to encode real numbers
Why Floating‐point
Can we represent natural numbers with fixed point
Can we represent integer numbers with fixed point
Why Floating‐point
You have 8 bits. How do you represent numbers between 0 and 63
Why Floating‐point
You have 8 bits. How do you represent numbers between 0 and 63
You have 8 bits. How do you numbers between 0 and 126
Why Floating‐point
You have 8 bits. How do you represent numbers between 0 and 63
You have 8 bits. How do you numbers between 0 and 126
Is 8‐bits sufficient to represent numbers between 0 and 63
How many different values can you
represent
10 digits
10 octal values
10 hex values
10 bits
Why Floating‐point
You want to represent a wide range with a fixed number of bits
Why Floating‐point
You want to represent a wide range with a fixed number of bits
Reason for floating‐point: You want to represent a variable range with
a fixed number of bits
Fixed vs Float
Overflow
5 bit fixed point, 2 bits integer, 3 bits fractional
Roundoff
Number system must not overflow (error unbounded)
Accumulation of round‐off errors must lie below tolerable region
5 bit floating point, 2 bits exponent, 3 bits mantissa
m
e bbbx ….02 21 }1,0{, ib
Fixed vs floating point
Fixed point:
Number system must not overflow (error unbounded)
Accumulation of round‐off errors must lie below tolerable region
Floating‐point similarities:
Number system must not overflow
Accumulation of round‐off errors must lie below tolerable region
Differences:
Bigger dynamic range
Underflow
Size of roundoff errors vary relative to the representable value
Floating point is not associative
Is floating‐point good
Notes vs IEEE 754 Standard Floating Point
Single precision:
Double precision
Notes vs IEEE 754 Standard Floating Point
Single precision:
Half precision
Notes vs IEEE 754 Standard Floating Point
IEEE standard
Implicit leading 1
Special codes:
NaN (0/0, sqrt(‐10))
Infinity (100/0, ‐100/0)
Exponent subtract a bias (127 for single gives range ‐126 to +127)
Important to remember
Floating point needs its representation defined
Floating‐point practice
Worksheet Q3
Floating‐point
range/precision/underflow/overflow
How do you increase range
How do you increase precision
What is overflow
What is underflow
Worksheet Q4
Floating‐point games
Floating point is not associative
Which answer is correct