revision lecture intro to it cosc1078 introduction to information technology extra lecture review...

Revision Lecture Intro to IT

COSC1078 Introduction to Information Technology

Extra Lecture

ReviewJames Harland

[email protected]


Introduction to IT

1 Introduction

2 Images

3 Audio

4 Video

5 Binary Representation WebTest 1, Assignment 1

6 Data Storage

7 Review/Machine Processing

8 Operating Systems WebLearn Test 1

9 Processes Assignment 2

10 Internet & Survey

11 Internet Security WebLearn Test 3

12 Future of IT Assignment 3, Peer and Self Assessment


Overview

Questions?

Mock Exam

Requested topics

Questions?


Intro to IT Schedule

Week Lecture 1 Lecture 2

12 Future of IT Future of IT

13 Tuesday 19th October

10.30-11.30

12.10.02

Review

Thursday 21st October

1.00-3.30

10.08.03

Mock Exam


Mock Exam

1.00-3.30 on Thursday 21st October in 10.08.03 Bring your own paper, pens, etc. Calculators and translation dictionaries allowed Answers will be available from me when you leave

Schedule:

1.00 Access to room 1.15 Reading time commences 1.30 Writing time commences 3.30 Exam concludes


Review Topics

Logic gates Hexadecimal to/from binary conversions Process vs. program Floating point Network layers Encryption Internet architecture Machine cycle


Hexadecimal

01010100001010101010100110100010101001101001010010100011100010101010100101111001001010…

AF136DF738CA23895389BCFE5C36A63B…


Hexadecimal

Notation for binary numbers More compact than 1001010001010101001010... NOT decimal (0-9) Base 16: 9 + 9 = 1 x 16 + 2 x120 0000 4 0100 8 1000 C 11001 0001 5 0101 9 1001 D 11012 0010 6 0110 A 1010 E 11103 0011 7 0111 B 1011 F 1111


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 0101 (looks like 5) encodes 1110 (looks like 6) encodes 2


Floating Point

sign bitMantissa

exponent

1 bit for sign3 bits for exponent4 bits for mantissa100.101


Floating Point

01111001: +ve 0.1001 shifted 111 (+3) places = 100.110011110: –ve 0.1110 shifted 001 (-3) places = -0.0001110

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


Gates and circuits

or

and

not1

0

00

0

0

0

0

0

1

11

1

11

1


Gates and circuits

No storage here

Results instantaneously available

Disappear when inputs change

How can a bit be `stored’?


Memory via `Flip flops’

or

and

not1

00

0 0 0

0

0

1



or

and

not0

11

1 1 1

1

0



Can design other versions of flip-flops

Shows how circuits can be designed using AND, OR, NOT (NAND, NOR, XOR, …) in combinations (gates)

Hierarchy and abstraction

Shows how electric circuits can store values


Fetch Decode Execute

FETCH

EXECUTE DECODE

Machinecycle


Two special registers

Instruction register: holds current instructionProgram counter: address of next instruction

Fetch: Put instruction specified by program counter into instruction registerIncrement program counter by two

Decode: Work out what to do

Execute: Perform the instruction


Processing

A0 15A1 6CA2 16A3 6DA4 50A5 56A6 30A7 C0A8 C0A9 00

Program Counter

InstructionRegister

A0Address Contents


Processing

A0 15A1 6CA2 16A3 6DA4 50A5 56A6 30A7 C0A8 C0A9 00

Program Counter

InstructionRegister

A0FETCH

156C


Processing

A0 15A1 6CA2 16A3 6DA4 50A5 56A6 30A7 C0A8 C0A9 00

Program Counter

InstructionRegister

A2FETCH

156C


Processing

A0 15A1 6CA2 16A3 6DA4 50A5 56A6 30A7 C0A8 C0A9 00

Program Counter

InstructionRegister

A2DECODE

156C

6C 2B


Processing

A0 15A1 6CA2 16A3 6DA4 50A5 56A6 30A7 C0A8 C0A9 00

Program Counter

InstructionRegister

A2

EXEC

156C

6C 2B

2B5


Processing

A0 15A1 6CA2 16A3 6DA4 50A5 56A6 30A7 C0A8 C0A9 00

Program Counter

InstructionRegister

A2 FETCH

166D


Processing

A0 15A1 6CA2 16A3 6DA4 50A5 56A6 30A7 C0A8 C0A9 00

Program Counter

InstructionRegister

A4 FETCH

166D


Processing

A0 15A1 6CA2 16A3 6DA4 50A5 56A6 30A7 C0A8 C0A9 00

Program Counter

InstructionRegister

A4 DECODE

166D


Processing

A0 15A1 6CA2 16A3 6DA4 50A5 56A6 30A7 C0A8 C0A9 00

Program Counter

InstructionRegister

A4 EXEC

166D

6D FF

FF6


Processing

A0 15A1 6CA2 16A3 6DA4 50A5 56A6 30A7 C0A8 C0A9 00

Program Counter

InstructionRegister

A6 FETCH

5056


Processing

A0 15A1 6CA2 16A3 6DA4 50A5 56A6 30A7 C0A8 C0A9 00

Program Counter

InstructionRegister

…


Processing

Program Counter

InstructionRegister

EXEC

B258

B4


Processing

Program Counter

InstructionRegister

EXEC

B258

58


Processing

Jump instructions change program counter

Can load any memory address into program counter (!!!)

Often use pipelining for efficiency Fetch next instruction while executing Processor doesn’t wait for fetch to complete

Can do more than one instruction …

Lecture 24: Review Intro to IT

Processes


Processes

A program is a static set of instructions

A processes is the execution of a program, which changes state over time.


Processes Executing in Context

Program Counter

InstructionRegister

CC ROM

RAM

Processor Memory Disk

00

CC


Processes Executing in Context

Program Counter

InstructionRegister

DD ROM

RAM

Processor Memory Disk

00

CC

DD

Lecture 19: Internet: Images Intro to IT

InternetLisa?Hi Dad!

Listen!Lisa?Hi Dad! Listen!


Internet Structure

Application Application

Transport Transport

Network

Link

Network

Link

Mordor sucks!

2 dor1 Mor3 suc 4 ks!

1 2 3 49 5 6 2

14

3

22

1

3

4

2 3 1 49 5 6 2

2 dor1 Mor3 suc 4 ks!

Mordor sucks!


Internet Structure

1 Mor

1

6

6


Network Layer (Internet Protocol) Real intelligence is in the network layer

Adds next destination to packet

Not complete list of addresses

Sends to next destination

Retrieves final destination packets for this node

Passes them to the transport layer

Routing tables can be updated when disconnections occur

Hop counts used to stop endless looping


Transport layer

Transmission Control Protocol (TCP) often used

User Datagram Protocol (UDP) becoming more common

TCP

Establishes connection first

Send and wait for acknowledgement

Reliable

Can adjust flow control to avoid congestion

Often best for email (which is not real-time)

Older


Transport layer

UDP

Doesn’t establish connection

Just sends and forget

Efficient

No congestion adjustment

Works well for DNS lookup

Often used for Voice over Internet Protocol (VoIP) applications such as Skype


Transmitting secrets

Question: How do you share a secret with someone you have never met?


Encryption

“new password is bumblebee”

“new password is bumblebee”

Send

Decrypt

Encrypt


Public Key Systems

Alice needs to know Bob's encryption key

Alice needs to know Charlie's encryption key

Alice needs to know David's encryption key ...

Alice needs to know everyone's encryption key

All encryption keys are made public

All decryption keys are kept private

Conclusion

Come to the mock exam

revision lecture intro to it cosc1078 introduction to information technology extra lecture review...

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