Lecture 24: Review Intro to IT COSC1078 Introduction to Information Technology Lecture 24 Review James Harland

Lecture 24: ReviewIntro to IT Introduction to IT 1-4 Introduction, Images, Audio, Video 5-6 Computer Fundamentals Assignment 1, WebLearn Test 1 7 Review 8 Operating Systems WebLearn Test 2 9 Operating Systems Assignment 2 10 Internet 11 Internet Security WebLearn Test 3 12 Review Assignment 3 Peer and Self Assessment

Lecture 24: ReviewIntro to IT Overview  Questions?  Mock Exam  Requested topics  Questions?

Lecture 24: ReviewIntro to IT Intro to IT Schedule WeekLecture 1Lecture 2 12Future of IT Review by request Various topics requested 13Mock Exam Wednesday 2 nd June

Lecture 24: ReviewIntro to IT Requests Received  Logic gates  Hexadecimal to/from binary conversions  Process vs. program  Floating point  Network layers  Encryption  Internet architecture  Machine cycle

Lecture 24: ReviewIntro to IT Mock Exam  on Wednesday 2 rd June in  Bring your own paper, pens, etc.  Calculators and translation dictionaries allowed  Answers will be available from me when you leave Schedule:  Access to room  Reading time commences  Writing time commences  1.00 Exam concludes

Lecture 24: ReviewIntro to IT Hexadecimal … AF136DF738CA BCFE5C36A63B…

Lecture24: ReviewIntro to IT Hexadecimal  Notation for binary numbers  More compact than  NOT decimal (0-9)  Base 16: = 1 x x C D A 1010 E B 1011 F 1111

Lecture 24: ReviewIntro to IT Excess Notation Bit patternValue  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 24: ReviewIntro to IT Floating Point sign bit Mantissa exponent 1 bit for sign 3 bits for exponent 4 bits for mantissa

Lecture 24: ReviewIntro to IT Floating Point : +ve shifted 111 (+3) places = : –ve shifted 001 (-3) places =  Mantissa: digit sequence (1 st digit always 1)  Exponent: where to put the.  This is generally given in ‘excess’ notation  Binary form of x 10 4

Lecture 24: ReviewIntro to IT Gates and circuits or and not

Lecture 24: ReviewIntro to IT Gates and circuits  No storage here  Results instantaneously available  Disappear when inputs change  How can a bit be `stored’?

Lecture 24: ReviewIntro to IT Memory via `Flip flops’ or and not

Lecture 24: ReviewIntro to IT Memory via `Flip flops’ or and not

Lecture 24: ReviewIntro to IT Memory via `Flip flops’  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

Lecture 24: ReviewIntro to IT Fetch Decode Execute FETCH EXECUTEDECODE Machine cycle

Lecture 24: ReviewIntro to IT Two special registers Instruction register: holds current instruction Program counter: address of next instruction Fetch: Put instruction specified by program counter into instruction register Increment program counter by two Decode: Work out what to do Execute: Perform the instruction

Lecture 24: ReviewIntro to IT Processing A0 15 A1 6C A2 16 A3 6D A4 50 A5 56 A6 30 A7 C0 A8 C0 A9 00 Program Counter Instruction Register A0 AddressContents

Lecture 24: ReviewIntro to IT Processing A0 15 A1 6C A2 16 A3 6D A4 50 A5 56 A6 30 A7 C0 A8 C0 A9 00 Program Counter Instruction Register A0 FETCH 156C

Lecture 24: ReviewIntro to IT Processing A0 15 A1 6C A2 16 A3 6D A4 50 A5 56 A6 30 A7 C0 A8 C0 A9 00 Program Counter Instruction Register A2 FETCH 156C

Lecture 24: ReviewIntro to IT Processing A0 15 A1 6C A2 16 A3 6D A4 50 A5 56 A6 30 A7 C0 A8 C0 A9 00 Program Counter Instruction Register A2 DECODE 156C 6C 2B

Lecture 24: ReviewIntro to IT Processing A0 15 A1 6C A2 16 A3 6D A4 50 A5 56 A6 30 A7 C0 A8 C0 A9 00 Program Counter Instruction Register A2 EXEC 156C 6C 2B 2B5

Lecture 24: ReviewIntro to IT Processing A0 15 A1 6C A2 16 A3 6D A4 50 A5 56 A6 30 A7 C0 A8 C0 A9 00 Program Counter Instruction Register A2 FETCH 166D

Lecture 24: ReviewIntro to IT Processing A0 15 A1 6C A2 16 A3 6D A4 50 A5 56 A6 30 A7 C0 A8 C0 A9 00 Program Counter Instruction Register A4 FETCH 166D

Lecture 24: ReviewIntro to IT Processing A0 15 A1 6C A2 16 A3 6D A4 50 A5 56 A6 30 A7 C0 A8 C0 A9 00 Program Counter Instruction Register A4 DECODE 166D

Lecture 24: ReviewIntro to IT Processing A0 15 A1 6C A2 16 A3 6D A4 50 A5 56 A6 30 A7 C0 A8 C0 A9 00 Program Counter Instruction Register A4 EXEC 166D 6D FF FF6

Lecture 24: ReviewIntro to IT Processing A0 15 A1 6C A2 16 A3 6D A4 50 A5 56 A6 30 A7 C0 A8 C0 A9 00 Program Counter Instruction Register A6 FETCH 5056

Lecture 24: ReviewIntro to IT Processing A0 15 A1 6C A2 16 A3 6D A4 50 A5 56 A6 30 A7 C0 A8 C0 A9 00 Program Counter Instruction Register …

Lecture 24: ReviewIntro to IT Processing Program Counter Instruction Register EXEC B258 B4

Lecture 24: ReviewIntro to IT Processing Program Counter Instruction Register EXEC B258 58

Lecture 24: ReviewIntro to IT 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: ReviewIntro to IT Processes

Lecture 24: ReviewIntro to IT Processes A program is a static set of instructions A processes is the execution of a program, which changes state over time.

Lecture 24: ReviewIntro to IT Processes Executing in Context Program Counter Instruction Register CC ROM RAM ProcessorMemory Disk 00 CC

Lecture 24: ReviewIntro to IT Processes Executing in Context Program Counter Instruction Register DD ROM RAM ProcessorMemory Disk 00 CC DD

Lecture 19: Internet: ImagesIntro to IT Internet Lisa? Hi Dad! Listen! Lisa? Hi Dad! Listen!

Lecture 24: ReviewIntro to IT Internet Structure Application Transport Network Link Network Link Mordor sucks! 2 dor1 Mor 3 suc4 ks! dor1 Mor 3 suc4 ks! Mordor sucks!

Lecture 24: ReviewIntro to IT Internet Structure 1 Mor 1 6 6

Lecture 24: ReviewIntro to IT 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

Lecture 24: ReviewIntro to IT 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 (which is not real-time) Older

Lecture 24: ReviewIntro to IT 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

Lecture 24: ReviewIntro to IT Transmitting secrets Question: How do you share a secret with someone you have never met?

Lecture 24: ReviewIntro to IT Encryption “new password is bumblebee” “new password is bumblebee” Send Decrypt Encrypt

Lecture 24: ReviewIntro to IT 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  Finish Assignment 3