COSC1078 Introduction to
Information Technology
Lecture 10
Binary Representation
James Harland
james.harland@rmit.edu.au
Lecture 10: Binary Representation
Intro to IT
Introduction
Who is this bloke?
Lecture 10: Binary Representation
Intro to IT
Introduction
Lecture 10: Binary Representation
Intro to IT
Overview
 Questions?
 WebLearn Test 1
 Assignment 1
 Binary Representation
 Questions?
Lecture 10: Binary Representation
Intro to IT
Introduction to IT
1 Introduction
2 Images
3 Audio
4 Video
WebLearnTest 1
5 Binary Representation
Assignment 1
6 Data Storage
7 Machine Processing
8 Operating Systems
WebLearn Test 1
9 Processes
Assignment 2
10 Internet
11 Internet Security
WebLearn Test 3
12 Future of IT
Assignment 3, Peer and Self Assessment
Lecture 10: Binary Representation
Intro to IT
Questions?
How did you spend 6-8 hours on this course
last week?
This week?
Lecture 10: Binary Representation
SE Fundamentals
Assessment Process
 Submit all assignments via Blackboard in the
Learning Hub
 Assignment 1 due 11.59pm Sunday 1st April
 Assignment 2 due 11.59pm Sunday 6th May
 Assignment 3 due 11.59pm Sunday 27th May
 Late assignments attract a penalty of 10% per
day late, up to a maximum of 50%
Lecture 910: Binary Representation
Intro to IT
Assignment
 Assignment will be in three parts
 Overall task is to produce a video
 Groups of up to 3
 Assessed by final video and group blog
 Part 1: images and audio (end of week 5)
 Part2: hardware (end of week 9)
 Part 3: reflection, research (end of week 12)
Lecture 10: Binary Representation
Intro to IT
Assignment 1
 Use GIMP (or a similar tool) to perform some
manipulations on an image
 Use Audacity to perform some manipulations on sound
 Use a movie making tool to produce something like (and
much better than!) ‘Lord of the Controllers 1 & 2’
 Email me your group and its name so that I can set up
a blog on the Learning Hub
Lecture 910: Binary Representation
Intro to IT
Overview
01010100001010101010100110100010101001101001010010
100011100010101010100101111001001010…
Lecture 10: Binary Representation
Intro to IT
History
 …
 Babbage’s Difference Engine (1849)
 Babbage’s Analytical Engine (1837-1871, never built)
 Turing’s Universal Machine (1936, mathematical model)
 Turing digital Boolean-logic multiplier (1937)
 Colossus (1943, destroyed 1945)
 ENIAC (1946)
 Von Neumann architecture (c. 1945)
 EDVAC (1949)
 CSIRAC (1949)
Lecture 10: Binary Representation
Intro to IT
Computer Memory
Cells of 8 bits each (one byte)
…
Most
significant
bit
address
Lecture 10: Binary Representation
…
Least
significant
bit
Intro to IT
Random Access Memory (RAM)
 Random access means any cell can be accessed at any
time (and in any order)
 Volatile – contents cleared when machine is switched off
 Very fast compared to other forms of memory
 DRAM: dynamic RAM (replenishes charges constantly)
 SDRAM: synchronous DRAM – faster still
 Often have small very fast caches and registers
Lecture 10: Binary Representation
Intro to IT
Magnetic Disk
 Thin spinning metal disk with magnetic coating
 Each disk contains a number of circular tracks
 Often several disks stacked on top of each other
 Cylinders made up of tracks made up of sectors
 Can have very large storage this way
 Slow access time!
Lecture 9: Data Storage Devices
Intro to IT
Magnetic Disk (Hard Disk)
Seek time: move heads from one track to another
Latency time: half time for complete disk rotation
Access time: seek time + latency time
Transfer rate: rate data can be read from disk
`Typical’ Hard disk
Seek time: 2ms to 15ms
Latency time: 8ms to 20ms
Transfer rate: 0.5 GB per second
Sounds fast, but is actually quite slow …
Lecture 9: Data Storage Devices
Intro to IT
Optical Disks (CDs, DVDs)
Laser readers rather than magnetic ones
Disks more error-tolerant than magnetic ones
Type
Features
Date
Storage
CD
“compact disk”
1984
800MB
DVD
Multiple layers
1995
15GB
Blu-ray
`blue laser’
2004
100GB
(405 vs 650 nm)
Lecture 9: Data Storage Devices
Intro to IT
Flash Drives
 Disks of all sorts are slow compared to other circuits
 Flash drives ‘write’ small electronic circuits
 Eventually decay after many changes of data
 Suitable for slow-changing data, not main memory
 Portable and much more resilient than disks
Lecture 9: Data Storage Devices
Intro to IT
Older Storage Types
Magnetic tape
`Floppy’ disk
(5.25’’ disk)
3.5’’ disk
Lecture 9: Data Storage Devices
Intro to IT
Binary Codes
“Meet me at Fred’s”
234
12.43434343
-620
0
Lecture 10: Binary Representation
1
1
0
0
Intro to IT
1
1
0
ASCII
American Standard Code for Information
Interchange
7-bit patterns to represent
 letters (upper and lower case)
 numbers
,.,;“$%@*&!?<>…
Total of 128 different characters
Lecture 10: Binary Representation
Intro to IT
ASCII
01001000
01100101
01101100
01101100
01101111
00101110
H
e
l
l
o
.
Hello!
Unicode: uses 16 bits, can do Chinese,
Japanese & Hebrew characters
Lecture 10: Binary Representation
Intro to IT
Numbers
Represented in binary notation
25 in ASCII is 00110010 00110101
8 bits per digit seems too much!
Can represent 256 different numbers in 8 bits …
Don’t want to add, multiply etc. in ASCII …
Remember that 1 + 1 = 10 …
Lecture 10: Binary Representation
Intro to IT
Two’s Complement
Bit pattern
Value
011
3
010
2
001
1
000
0
111
-1
110
-2
101
-3
100
-4
Lecture 10: Binary Representation
How do you store
negative numbers?
Intro to IT
Two’s Complement
0 first means +ve (sign bit)
1 first means –ve
+ve: Count from 0 up to 01n-1
-ve: Start from
1n
down to
3 is 011, -3 is 101
2 is 010, -2 is 110
1 is 001, -1 is 111
Lecture 10: Binary Representation
10n-1
Bit pattern
Value
011
3
010
2
001
1
000
0
111
-1
110
-2
101
-3
100
-4
Intro to IT
Two’s Complement
Bit pattern
Value
011
3
010
2
011 + 111 = 1010
001
1
Answer is 010, ie 2.
000
0
111
-1
110
-2
101
-3
100
-4
1 + 2: add in obvious way
3 – 1: calculate as 3 + (-1)
Can add and subtract with
the same circuits
Lecture 10: Binary Representation
Intro to IT
Excess Notation
A different encoding of the
numbers
“naive” bit pattern encodes 4
more than actual value
100 (looks like 4) encodes 0
101 (looks like 5) encodes 1
110 (looks like 6) encodes 2
Lecture 10: Binary Representation
Bit pattern
Value
111
3
110
2
101
1
100
0
011
-1
010
-2
001
-3
000
-4
Intro to IT
Floating Point
exponent
sign bit
Mantissa
100.101
1 bit for sign
3 bits for exponent
4 bits for mantissa
Lecture 10: Binary Representation
Intro to IT
Floating Point
 Mantissa: digit sequence (1st digit always 1)
 Exponent: where to put the .
 This is generally given in ‘excess’ notation
 Binary form of 2.423 x 104
01011001 means +ve 0.1001 shifted 101 place
= 1.001
Lecture 10: Binary Representation
Intro to IT
Truncation Errors
Beware adding small numbers to large ones!
Finite length of encoding means that
sometimes digits are lost
Not often a problem, but can be …
Lecture 10: Binary Representation
Intro to IT
Parity Bits
 Add a ‘parity bit’ to each byte
 Odd parity: make total of 1s in all 9 bits odd
 Even parity: make total of 1s in all 9 bits even
 If parity is wrong, then an error has occurred
Lecture 10: Binary Representation
Intro to IT
Conclusion
 Get Assignment and WebTest done this week
 Do online quizzes later this week
 Keep reading! (book particularly)
Lecture 10: Binary Representation
Intro to IT