2. Lecture 10: System Fundamentals Intro to IT COSC1078 Introduction to Information Technology Lecture 10 System Fundamentals James Harland james.harland@rmit.edu.au

3. Lecture 10: Computer FundamentalsIntro to IT Introduction to IT 1-4 Introduction, Images, Audio, Video 5 Computer Fundamentals Assignment 1, WebLearn Test 1 Tuesday March 30 th, Wednesday March 31 st (no classes Thursday 1 st April, Tuesday 6 th April, Wednesday 7 th April) 6 Computer Fundamentals Tuesday April 13 th, Wednesday April 14th 7 Computer Fundamentals /Review/Catch Up 8 Operating Systems WebLearn Test 1 9 Operating Systems Assignment 2 10 Internet 11 Internet Security WebLearn Test 3 12 Future of ITAssignment 3, Peer and Self Assessment

4. Lecture 10: Computer FundamentalsIntro to IT Overview  Questions?  WebLearn Test 1  Computer Fundamentals  Questions?

5. Lecture 10: Computer FundamentalsIntro to IT Web Test 1  Now Week 5 (this week)  All quizzes (practice tests) available now  Test available now  Content will be on weeks 2-4 Images Audio Video

6. Lecture 10: Computer FundamentalsIntro to IT Assignment 1  Due date is 9.00am on Monday 12 th April (1 st day of Week 6)  Can submit now if you wish …  Do submit something soon  Only PDFs for report SUBMIT IT! NOW!!

7. Lecture 10: Computer FundamentalsIntro to IT Introduction

8. Lecture 10: Computer FundamentalsIntro to IT Overview 01010100001010101010100110100010101001101001010010 100011100010101010100101111001001010…

9. Lecture 10: Computer FundamentalsIntro to IT What do computers do?  Compute!  Input/Output  Processing  Memory

10. Lecture 10: Computer FundamentalsIntro 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)

11. Lecture 10: Computer FundamentalsIntro to IT Computer Memory Cells of 8 bits each (one byte) Most significant bit Least significant bit … … address

12. Lecture 10: Computer FundamentalsIntro to IT Binary Codes “Meet me at Fred’s” 234 12.43434343 -620 0 0 111001

13. Lecture 10: Computer FundamentalsIntro 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

14. Lecture 10: Computer FundamentalsIntro to IT ASCII 01001000 H 01100101 e 01101100 l 01101111 o 00101110. Hello! Unicode: uses 16 bits, can do Chinese, Japanese & Hebrew characters

15. Lecture 10: Computer FundamentalsIntro 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 …

16. Lecture 10: Computer FundamentalsIntro to IT Two’s Complement How do you store negative numbers? Bit patternValue 0113 0102 0011 0000 111 110-2 101-3 100-4

17. Lecture 10: Computer FundamentalsIntro to IT Two’s Complement Bit patternValue 0113 0102 0011 0000 111 110-2 101-3 100-4 0 first means +ve (sign bit) 1 first means –ve +ve: Count from 0 up to 01 n-1 -ve: Start from 1 n down to 10 n-1 3 is 011, -3 is 101 2 is 010, -2 is 110 1 is 001, -1 is 111

18. Lecture 10: Computer FundamentalsIntro to IT Two’s Complement Bit patternValue 0113 0102 0011 0000 111 110-2 101-3 100-4 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

19. Lecture 10: Computer FundamentalsIntro 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

20. Lecture 10: Computer FundamentalsIntro to IT Floating Point sign bit Mantissa exponent 1 bit for sign 3 bits for exponent 4 bits for mantissa 100.101

21. Lecture 10: Computer FundamentalsIntro to IT Floating Point 01011001 means +ve 0.1001 shifted 101 place = 1.001  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

22. Lecture 10: Computer FundamentalsIntro 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 …

23. Lecture 10: Computer FundamentalsIntro 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

24. Lecture 10: Computer FundamentalsIntro to IT Conclusion  Web Test this week (week 5)  Do online quizzes later this week  Keep reading! (book particularly)