lecture 14: review intro to it cosc1078 introduction to information technology lecture 14 revision...
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Lecture 14: Review Intro to IT
COSC1078 Introduction to Information Technology
Lecture 14
Revision and ReviewJames Harland
Lecture 14: Review Intro 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 Future of IT Assignment 3, Peer and Self Assessment
Lecture 14: Review Intro to IT
Overview
Questions?
Floating point numbers
“Week 6 lectures”
Questions?
Lecture 14: Review 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 0101 (looks like 5) encodes 1110 (looks like 6) encodes 2….
Lecture 14: Review Intro to IT
Floating Point
sign bitMantissa
exponent
1 bit for sign3 bits for exponent4 bits for mantissa100.101
Lecture 14: Review 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 14: Review Intro to IT
Memory
Memory differs in performance and cost
Processor is typically much faster than memory
Lecture 14: Review Intro to IT
Memory
Arranged as a hierarchy of cache
Level 1Level 2
Level 3
Main Memory
Lecture 14: Review Intro to IT
Machine Instructions
1. Move first value from memory into register 12. Move second value from memory into
register 23. If register 2 is zero, go to Step 64. Divide register 1 by register 2 & store result
in register 35. Store register 3 value in memory6. Stop
“Divide two numbers”
Lecture 14: Review Intro to IT
Instructions in Binary?01010100001010101010100110100010101001101001010010100011100010101010100101111001001010…
LOAD register 1LOAD register 2JUMP ….STORE ….
1010110010110011000100100011001100111111
MEMORY
Lecture 14: Review Intro to IT
One Scheme
16-bit operation codes (simple example)
Operation Code(4 bits)
Operand (12 bits)
Represent as 4 Hexadecimal numbers (0-9,A-F)Each instruction is two bytes long
Lecture 14: Review Intro to IT
One Scheme
156C LOAD register 5 from memory 6C166D LOAD register 6 from memory 6D5056 ADD register 5 & 6 & store in register 0306E STORE register 0 to memory 6EC000 HALT....(up to 216 = 65,536 different instructions)
Lecture 14: Review Intro to IT
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
Lecture 14: Review Intro to IT
Processing
A0 15A1 6CA2 16A3 6DA4 50A5 56A6 30A7 C0A8 C0A9 00
Program Counter
InstructionRegister
A0Address Contents
Lecture 14: Review Intro to IT
Processing
A0 15A1 6CA2 16A3 6DA4 50A5 56A6 30A7 C0A8 C0A9 00
Program Counter
InstructionRegister
A0FETCH
156C
Lecture 14: Review Intro to IT
Processing
A0 15A1 6CA2 16A3 6DA4 50A5 56A6 30A7 C0A8 C0A9 00
Program Counter
InstructionRegister
A2FETCH
156C
Lecture 14: Review Intro to IT
Processing
A0 15A1 6CA2 16A3 6DA4 50A5 56A6 30A7 C0A8 C0A9 00
Program Counter
InstructionRegister
A2DECODE
156C
6C 2B
Lecture 14: Review Intro to IT
Processing
A0 15A1 6CA2 16A3 6DA4 50A5 56A6 30A7 C0A8 C0A9 00
Program Counter
InstructionRegister
A2
EXEC
156C
6C 2B
2B5
Lecture 14: Review Intro to IT
Processing
A0 15A1 6CA2 16A3 6DA4 50A5 56A6 30A7 C0A8 C0A9 00
Program Counter
InstructionRegister
A2 FETCH
166D
Lecture 14: Review Intro to IT
Processing
A0 15A1 6CA2 16A3 6DA4 50A5 56A6 30A7 C0A8 C0A9 00
Program Counter
InstructionRegister
A4 FETCH
166D
Lecture 14: Review Intro to IT
Processing
A0 15A1 6CA2 16A3 6DA4 50A5 56A6 30A7 C0A8 C0A9 00
Program Counter
InstructionRegister
A4 DECODE
166D
Lecture 14: Review Intro to IT
Processing
A0 15A1 6CA2 16A3 6DA4 50A5 56A6 30A7 C0A8 C0A9 00
Program Counter
InstructionRegister
A4 EXEC
166D
6D FF
FF6
Lecture 14: Review Intro to IT
Processing
A0 15A1 6CA2 16A3 6DA4 50A5 56A6 30A7 C0A8 C0A9 00
Program Counter
InstructionRegister
A6 FETCH
5056
Lecture 14: Review Intro to IT
Processing
A0 15A1 6CA2 16A3 6DA4 50A5 56A6 30A7 C0A8 C0A9 00
Program Counter
InstructionRegister
…
Lecture 14: Review Intro to IT
Memory-mapped I/O
Program Counter
InstructionRegister
C4 EXEC
3634
34 FF
FF6
Just like writing to a memory address
Lecture 14: Review Intro to IT
Direct Memory Access
Direct Memory Access means that
doesn’t have to wait for the