1. Lecture 24: Review Intro to IT COSC1078 Introduction to Information Technology Lecture 24 Review James Harland james.harland@rmit.edu.au

2. 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

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

4. 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

5. 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

6. Lecture 24: ReviewIntro to IT Mock Exam  10.30-1.00 on Wednesday 2 rd June in 12.08.02  Bring your own paper, pens, etc.  Calculators and translation dictionaries allowed  Answers will be available from me when you leave Schedule:  10.30 Access to room  10.45 Reading time commences  11.00 Writing time commences  1.00 Exam concludes

7. Lecture 24: ReviewIntro to IT Hexadecimal 01010100001010101010100110100010101001101001010010 100011100010101010100101111001001010… AF136DF738CA23895389BCFE5C36A63B…

8. Lecture24: ReviewIntro to IT Hexadecimal  Notation for binary numbers  More compact than 1001010001010101001010...  NOT decimal (0-9)  Base 16: 9 + 9 = 1 x 16 + 2 x12 0 0000 4 0100 8 1000 C 1100 1 0001 5 0101 9 1001 D 1101 2 0010 6 0110 A 1010 E 1110 3 0011 7 0111 B 1011 F 1111

9. Lecture 24: ReviewIntro to IT Excess Notation Bit patternValue 1113 1102 1011 1000 011 010-2 001-3 000-4  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

10. Lecture 24: ReviewIntro to IT Floating Point sign bit Mantissa exponent 1 bit for sign 3 bits for exponent 4 bits for mantissa 100.101

11. Lecture 24: ReviewIntro to IT Floating Point 01111001: +ve 0.1001 shifted 111 (+3) places = 100.1 10011110: –ve 0.1110 shifted 001 (-3) places = -0.0001110  Mantissa: digit sequence (1 st digit always 1)  Exponent: where to put the.  This is generally given in ‘excess’ notation  Binary form of -2.423 x 10 4

12. Lecture 24: ReviewIntro to IT Gates and circuits or and not 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1

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

14. Lecture 24: ReviewIntro to IT Memory via `Flip flops’ or and not 1 0 0 0 0 0 0 0 1

15. Lecture 24: ReviewIntro to IT Memory via `Flip flops’ or and not 0 1 1 1 1 1 1 0

16. 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

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

18. 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

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

26. 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

27. 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

28. 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

29. 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 …

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

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

32. 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 …

33. Lecture 24: ReviewIntro to IT Processes

34. 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.

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

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

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

38. Lecture 24: ReviewIntro to IT Internet Structure Application Transport Network Link Network Link Mordor sucks! 2 dor1 Mor 3 suc4 ks! 1 2 3 4 956 2 1 4 3 2 2 1 3 4 2 3 1 4 956 2 2 dor1 Mor 3 suc4 ks! Mordor sucks!

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

40. 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

42. 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 email (which is not real-time) Older

43. 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

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

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

46. 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

47. Conclusion  Come to the mock exam  Finish Assignment 3