Lecture 10: Binary Representation Intro to IT

COSC1078 Introduction to Information Technology

Lecture 10

Binary RepresentationJames 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 SE Fundamentals

Questions?

How did you spend 6-8 hours on this course last week?

This week?

Lecture 910: Binary Representation Intro to IT

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 10: 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 910: 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 10: Binary Representation Intro to IT

Overview

01010100001010101010100110100010101001101001010010100011100010101010100101111001001010…

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

Least significant bit

……

address

Lecture 10: Binary Representation 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 9: Data Storage Devices 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 anotherLatency time: half time for complete disk rotationAccess time: seek time + latency timeTransfer rate: rate data can be read from disk

`Typical’ Hard disk

Seek time: 2ms to 15msLatency time: 8ms to 20msTransfer 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’

(405 vs 650 nm)

2004 100GB

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 10: Binary Representation Intro to IT

Binary Codes

“Meet me at Fred’s”23412.43434343-620

0

0

111 001

Lecture 10: Binary Representation Intro to IT

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 H01100101 e01101100 l01101100 l01101111 o00101110 .

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

How do you store negative numbers?

Bit pattern Value

011 3

010 2

001 1

000 0

111 -1

110 -2

101 -3

100 -4

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

0 first means +ve (sign bit)

1 first means –ve

+ve: Count from 0 up to 01n-1

-ve: Start from 1n down to 10n-1

3 is 011, -3 is 101

2 is 010, -2 is 110

1 is 001, -1 is 111

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

1 + 2: add in obvious way

3 – 1: calculate as 3 + (-1)

011 + 111 = 1010

Answer is 010, ie 2.

Can add and subtract with

the same circuits

Lecture 10: Binary Representation Intro to IT

Excess Notation

Bit pattern Value

111 3

110 2

101 1

100 0

011 -1

010 -2

001 -3

000 -4

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 Intro to IT

Floating Point

sign bitMantissa

exponent

1 bit for sign

3 bits for exponent

4 bits for mantissa

100.101

Lecture 10: Binary Representation Intro to IT

Floating Point

01011001 means +ve 0.1001 shifted 101 place

= 1.001

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

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)