Principles of Computing and Information Technology Lecture 2 - Hardware

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Principles of Computing and Information
TechnologyLecture 2 - Hardware

• Andy Dawson
• School of Library, Archive Information Studies,
  UCL

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What we will cover today

• History and development of computers
• Computer architecture
• Processors
• Memory
• I/O devices/peripherals
• input devices
• output devices
• storage devices

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How computers developed
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But also...

• 1945 John Von Neumann - critical paper on
  computing principles
• The Von Neumann Concept - The computer as a
• Sequentially-executed
• Stored Program
• Machine

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Von Neumann principles

• The architecture of a computer consists of three
  main parts CPU, memory, and a connecting device
  (data bus) which can transmit a single data word
  at a time between the two.
• The memory is a linear vector of data words which
  are referenced by sequential addressing.

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Von Neumann principles

• The program which directs the activities of the
  CPU is stored in the same memory as the data
  which is to be manipulated by the program - the
  computer is a stored program machine.

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Von Neumann principles

• There is no distinction between data and
  instructions, nor indeed between one data type
  and another. There is no inherent meaning to the
  words which are stored in memory. The
  interpretation of a word is fixed only by the
  context at the time the word is fetched from
  memory.

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Von Neumann principles

• Since the device connecting the memory and CPU
  can only transmit one word at a time,
  instructions must be executed sequentially.

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Von Neumann principles

• Just an idea...
• ...But the basis for the physical manifestation
  of actual computing
• Persistence of the Von Neumann model
• Represented in computer system architecture
• Modern divergence from the model

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Computer system architecture

• How the computer is physically built (at the
  electronic component level)
• Specifies/describes the components and how those
  components interact
• Black box models vs digital logic models

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A black box diagram
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Second-level block diagram
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Third-level block diagram
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Fourth-level block diagram
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The logic gate

• Basis of all computers
• Physical piece of circuitry
• Fixed inputs
• Predictable outputs
• Truth tables
• Linked together to performmeaningful functions

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A half-adder
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A full adder
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The Fetch-execute cycle

• What is it?
• Time taken to fetch an instruction from memory
  and execute it in the processor
• Execute possibilities - determined by
  instruction set
• Speed of execution - determined by internal clock
  (cycle time)
• Why is it so important?

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Relative speeds
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The Von Neumann bottleneck

• Speed is relative!
• Working round the problems
• RISC/CISC
• Caching
• Parallel processing
• Modern solutions

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Memory types

• Primary vs Secondary
• Volatile vs nonvolatile
• Memory types
• RAM, ROM, PROM, EPROM, EEPROM
• Chips, SIMMs, DIMMs, pins, parity
• SRAM, DRAM, VRAM, WRAM, EDO RAM, SDRAM, DDR RAM
  etc etc etc!
• Banking, matching and compatibility

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Input devices

• Data input vs data capture
• Data input is the original creation of data in
  digital form
• Data capture is the conversion of existing data
  into digital form
• Input device types

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Input devices
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Output devices

• Hard vs Soft copy
• Hard copy is permanent and portable
• Soft copy is not!
• Output device types

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Printers

• Character/line vs page
• Impact vs non-impact
• Daisywheel, Dot matrix, Line printer
• Inkjet, Bubblejet
• Laser
• Thermal transfer
• Plotters

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Output devices

• VDU
• Cathode ray (CRT)
• LCD
• TFT
• Plasma
• Voice
• COM
• Others?

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Storage devices

• Basic storage formats
• Sequential
• Cyclic
• Blocked (array)
• Serial and random access

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Storage devices

• Media
• Magnetic
• Optical
• Phase change
• Magneto-optical
• Solid state

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Storage formats

• The need for formatting
• Magnetic tape
• Cassette/cartridge, reel, DAT
• Magnetic disk
• Floppy, Hard,
• Superfloppies, portables/removeables
• Optical
• CD-R (WORM), CD-RW, DVD, DVD-RW
• Solid-state devices

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Storage devices

• The future and development trends
• Sticks, cards, and who knows what galore?
• The demise of the disk?
• Recentralisation?
• Fundamental considerations
• Usage
• Speed of access
• Cost
• Volume

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This weeks practicals

• Excel basics
• Simple handout, backup materials on the web see
  http//www.ucl.ac.uk/isd/common/resources/excelMor
  e detail (and more complex operations) later in
  the term
• And/or do part of the ECDL course at
  http//www.ucl.ac.uk/isd/common/resources/online-l
  earning/skills-suite

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Thats it for this week!

• History of Computing site - http//ei.cs.vt.edu/h
  istory/
• Or a bit gaudier http//www.thocp.net/
• How Stuff Works (tech stuff explained!)http//com
  puter.howstuffworks.com/
• Next week Software.