Lecture 10: System Fundamentals Intro to IT COSC1078 Introduction to Information Technology Lecture 10 System Fundamentals James Harland [email protected]
Lecture 10: System Fundamentals Intro to IT COSC1078 Introduction to Information Technology Lecture 10 System Fundamentals James Harland [email protected].
Dec 20, 2015
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Lecture 10: System Fundamentals Intro to IT
COSC1078 Introduction to Information Technology
Lecture 10
System FundamentalsJames Harland
Lecture 10: Computer Fundamentals
Intro to IT
Introduction to IT
1-4 Introduction, Images, Audio, Video
5 Computer Fundamentals Assignment 1, WebLearn Test 1
Tuesday March 30th, Wednesday March 31st
(no classes Thursday 1st April, Tuesday 6th April, Wednesday 7th April)
6 Computer Fundamentals
Tuesday April 13th, 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 IT Assignment 3, Peer and Self Assessment
Lecture 10: Computer Fundamentals
Intro to IT
Overview
Questions?
WebLearn Test 1
Computer Fundamentals
Questions?
Lecture 10: Computer Fundamentals
Intro 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
Lecture 10: Computer Fundamentals
Intro to IT
Assignment 1
Due date is 9.00am on Monday 12th April (1st day of Week 6)
Can submit now if you wish …
Do submit something soon
Only PDFs for report
SUBMIT IT!NOW!!
Lecture 10: Computer Fundamentals
Intro to IT
Introduction
Lecture 10: Computer Fundamentals
Intro to IT
Overview
01010100001010101010100110100010101001101001010010100011100010101010100101111001001010…
Lecture 10: Computer Fundamentals
Intro to IT
What do computers do? Compute!
Input/Output
Processing
Memory
Lecture 10: Computer Fundamentals
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: Computer Fundamentals
Intro to IT
Computer Memory
Cells of 8 bits each (one byte)
Most significant bit
Least significant bit
……
address
Lecture 10: Computer Fundamentals
Intro to IT
Binary Codes
“Meet me at Fred’s”23412.43434343-620
0
0
111 001
Lecture 10: Computer Fundamentals
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: Computer Fundamentals
Intro to IT
ASCII
01001000 H01100101 e01101100 l01101100 l01101111 o00101110 .
Hello!
Unicode: uses 16 bits, can do Chinese, Japanese & Hebrew characters
Lecture 10: Computer Fundamentals
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: Computer Fundamentals
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: Computer Fundamentals
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: Computer Fundamentals
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: Computer Fundamentals
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: Computer Fundamentals
Intro to IT
Floating Point
sign bitMantissa
exponent
1 bit for sign
3 bits for exponent
4 bits for mantissa
100.101
Lecture 10: Computer Fundamentals
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: Computer Fundamentals
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: Computer Fundamentals
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: Computer Fundamentals
Intro to IT
Conclusion
Web Test this week (week 5)
Do online quizzes later this week
Keep reading! (book particularly)
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