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August 2004                                Slide 1
                Standard Grade Computing

 All the physical parts of a computer like a mouse, printer,
 keyboard and monitor are called hardware. A single
 item of hardware is called a device.

                     Eg. Keyboard, mouse
                                            Input Devices

              Backing Storage
                                             Processor                 Main Memory

Eg. Hard Disk, Floppy Disk

                                           Output Devices
                                                               Eg. Monitor, Printer

   August 2004                                                                        Slide 2
                                    Standard Grade Computing
          Types of Computers

Mainframe - The biggest type of
computer. Fills a whole room, costs
hundreds of thousands of pounds and
is used by banks, large universities and
large businesses.

                               Desktop - A ‘normal’
                               computer system that
                               fits on or under a desk.

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                       Standard Grade Computing
Types of computers (continued)

Laptop/Notebook - A portable
computer designed to be moved about
easily. It is lightweight, powered by
batteries, uses a flat screen, has a
standard keyboard with a touch pad
and may have wireless networking built

                 Palmtop - A portable computer designed to
                 fit in the palm of your hand. Has a
                 handwriting input system and on-screen
                 keyboard. Used as a diary, organiser, word
                 processor, calculator and for
   August 2004                                           Slide 4
                            Standard Grade Computing
                  A Computer System

A typical Computer System will have all of the
following devices:
•Base Unit (Including CPU & RAM)
Extras will be:
•CD-ROM (or DVD) Drive
•Speakers (with sound card)

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                      Standard Grade Computing
                       The Base Unit

Can be a Desktop Unit, or a Tower Unit
and will contain the following devices:
         Central Processing Unit (CPU)
Main Memory                    Network Card
               Floppy Disk Drive
         Hard Disk Drive
Graphics Card                  Sound Card

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                        Standard Grade Computing
               The Central Processing Unit

A Central Processing Unit (CPU) is contained on a single
chip. The CPU carries out: sorting, searching, calculating
and decision making. Examples are Intel Pentium and AMD
Athlon. The CPU is a microprocessor.

To find out more about microprocessors, take a look at:

 August 2004                                      Slide 7
                      Standard Grade Computing
                    MAIN MEMORY

Main memory refers to a group of chips inside the
computer. When you run any program, such as a word
processor or a game, the program is loaded into main
memory from the hard disk or CD ROM.

Memory is organised into small ‘compartments’ called
storage locations. Each storage location can hold a small
amount of information and is identified by a unique address.

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                      Standard Grade Computing
Main memory is made up of two types of memory chips:

1. RAM (Random Access Memory)
     • Contents are lost when the computer is switched
       off. (Volatile)
     • Can be changed – The CPU can write to memory.
     • Used to store programs and data temporarily.

2. ROM (Read Only Memory)
     • Contents not lost when the computer is switched
       off. (Non-Volatile)
     • Can not be changed – The CPU can only read from
     • Used to store the Operating System on palmtop

  August 2004                                    Slide 9
                     Standard Grade Computing
Effects Of Changes In Technology

Changes in technology have led to computers which are
faster, cheaper, smaller and more reliable. This is
         1. Price of memory chips has decreased.
         2. Size and speed of memory (RAM & ROM) has
         3. CPUs work faster and can handle more data in a
         single operation.
         4. Powerful computers can now be made very small.

  August 2004                                       Slide 10
                        Standard Grade Computing
    Q Q       uick   uestions
    1. The microprocessor which controls all the computer’s
    activities is part of the CPU. What do the letters CPU stand

    2. Describe one task done by the CPU.

    3. A Computer’s main memory is made up of both ROM and
    RAM. What do the letters ROM and RAM stand for?

    4. In a computer, the CPU is often a microprocessor chip.
            What is a chip?

    5. Clark is a news reporter working for the Daily Globe. He
    has a palmtop computer to help him take notes. Why might
    Clark find this type of computer particularly useful?

August 2004                                                        Slide 11
                          Standard Grade Computing
Backing Storage
Backing storage is where you store and save programs and
Backing Storage   Backing Storage
                                                     Used For     Capacity
    Media             Devices
   Hard disk       Hard disk drive        Storing main programs   20-200Gb
  Floppy disk     Floppy disk drive           Saving data files    1.44Mb
 Magnetic tape       Tape drive               Taking backups      4-200Gb
   CD ROM         CD ROM drive                Games & Music        800Mb
     DVD             DVD drive                 Movies/Music       4.7 - 17Gb

   August 2004                                                    Slide 12
                          Standard Grade Computing
Backing Storage Media

1.    Hard disk
                  A circular metal disk coated
                  with magnetic material.

Advantages:       Fast access to data
                  Stores a lot of data (High Capacity).

Disadvantages:    Can be corrupted (although normally

Type of Access:   Random.

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                   Standard Grade Computing
2. Floppy disks
       A thin plastic disk coated with magnetic material
       and enclosed in a hard plastic cover.
       Before you can use a floppy disk it must be
       formatted. Formatting produces invisible circles
       (tracks) and lines (sectors) of magnetism on the
       surface of the disk.
                Unformatted                              Formatted

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                              Standard Grade Computing
2. Floppy disks (Continued)

Advantages:       Cheap
                  Fast access to data (slower than hard
                  disc or CD).

Disadvantages:    Can be corrupted easily
                  Doesn’t store much data (Low

Type of Access:   Random.

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                    Standard Grade Computing
3.         Magnetic tape

           Similar to cassette tape.

           Advantages:           Can store lots of data (High

           Disadvantages:        Slow to access.

           Type of Access:       Sequential (Serial).

     August 2004                                          Slide 16
                            Standard Grade Computing
4. CD ROM - Compact Disk Read Only Memory.
            This looks just like a music CD.

Advantages:       Can store huge amounts of information
                  compared to a floppy disk (but not as
                  much as a hard disk).
                  Fast access to data.

Disadvantages:    Data cannot be changed.

Examples:         Encyclopaedias, databases, historical

Type of Access:   Random.

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                     Standard Grade Computing
5. DVD ROM – Digital Versatile Disc Read Only Memory.

   Similar to Compact Disc (CD), a DVD holds a minimum
   of 4.7Gb of data, enough for a full-length movie. New
   technology allows up to 17Gb of data to be store on
   one DVD disc.

Advantages:       Can store more than CD.

Disadvantages:    Data cannot be changed.

Examples:         Film rental.

Type of Access:   Random.

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                     Standard Grade Computing
  6. Recordable Media

  •      CD-R are blank CDs which can be
         recorded on once only, then the data is
         stored permanently.
  •      CD-RW are blank CDs which can be
         written and erased as many times as you
  •      DVD-R are blank DVD which can be
         written once.
  •      DVD-RW are blank DVDs which can be
         erased and recorded over many times.

August 2004                                    Slide 19
                    Standard Grade Computing
7. USB Flash Drives

These are small, portable
devices which plug into a
computer’s USB port and work
like a portable disc drive with
up to 2GB of storage capacity.
USB flash drives have less
storage capacity than a hard
drive, but they are smaller,
portable and more durable
because they do not contain any
internal moving parts. They
store much more than a floppy
disc and do not corrupt as

August 2004                                       Slide 20
                       Standard Grade Computing
 Summary of Backing Storage Devices

Backing Storage    Speed                 Cost      Capacity

   Hard disk      Very Fast          £50 - £200    20-200Gb
  Floppy disk       Slow                  20p       1.44Mb
 Magnetic tape    Slowest              £5 - £50    4-200Gb
   CD ROM           Fast                  30p       800Mb
     DVD            Fast                  50p      4.7 - 17Gb
  USB Drive       Very Fast           £20-£150    128Mb – 2Gb

 August 2004                                             Slide 21
                       Standard Grade Computing
Sequential Access (Serial Access)
Accessing data in the same sequence as it was
originally stored. This type of access is very slow.
Example: Tape.

                Random Access (Direct Access)
                You can access any data from a disk
                directly because the read/write head on
                the disk drive can jump straight to the
                track where the data is stored, without
                having to read all the data in between. This
                type of access is very fast.
                Examples: Floppy Disk, Hard Disk, CD, DVD.
  August 2004                                          Slide 22
                       Standard Grade Computing
This is the use of sound, animated images, video and
graphics. Used in interactive learning systems and games.

Multimedia systems requires the following
 1. Sound input: using a sound card, from a microphone,
 or CD player.
 2. Graphical input: using a graphics card, from a video
 or still digital camera.
 3. A range of high quality output devices: high
 resolution monitor, stereo speakers.
 4. Large amount of RAM.
 5. High speed and high capacity backing storage.
 6. A fast processor.

  August 2004                                     Slide 23
                     Standard Grade Computing
H       omework   Questions

1. What is multimedia?

2. Why is sequential access slower than direct access?

   August 2004                                           Slide 24
                          Standard Grade Computing
                         Input Devices                Not This

1.           Mouse

2.          Keyboard
            The input device used most often with a computer

3.          Track ball
            An upside down mouse. Used in
            portable computers. Why?

     August 2004                                            Slide 25
                           Standard Grade Computing
4.        Joystick
          Used for game play.

5.        Graphics tablet
          A flat pressure-sensitive board with a pen or
          pointer connected to it. Used in Computer
          Aided Design.

 August 2004                                         Slide 26
                        Standard Grade Computing
6.     Touch-sensitive screen

       Uses include information guides,
       tourism and museums.

7.     Scanner

                             A scanner allows you to input
                             drawings, photographs, bar
                             codes or text directly into a

     August 2004                                       Slide 27
                         Standard Grade Computing
8. Trackpad
   Also known as a Touchpad, a trackpad is used with
   a laptop computer in place of a mouse to move the
   cursor around the screen.

9. Web Cam
                  Used to view people or places on
                  the internet.

August 2004                                    Slide 28
                   Standard Grade Computing
10. Digital Still Camera
A camera without film. Images are recorded on sensors
and stored in memory. Images can then be transferred to
a computer for viewing or printed out on a high quality
colour printer, or uploaded to a web site.

                 11. Digital Video Camera
                 Video is stored digitally on tape. It can
                 be transferred to a computer for editing
                 with software such as iMovie or Windows
                 Movie Maker. The finished movie can be
                 transferred back to the tape for viewing
                 or saved as a computer file.
  August 2004                                    Slide 29
                     Standard Grade Computing
12.     Voice Recognition
        You can to give instructions to the
        computer by simply speaking to it. You
        will need a computer fitted with a
        microphone and voice recognition
        software. The microphone must be
        connected through a sound card.

13.     Hand Writing Recognition
                      Used in palmtop computers for
                      input. User ‘writes’ on the screen,
                      often in a special script, and the
                      computer turns it into text. (The
                      computer often makes mistakes, but
                      technology is improving)
  August 2004                                     Slide 30
                       Standard Grade Computing
H        omework   Q uestions
1.      Disks must be formatted before they can be used to
save data.. Draw a diagram to show what a floppy disk
looks like before and after it has been formatted.

2.        Which of these input devices (TRACKBALL
          MOUSE         JOYSTICK)
          would be used with:
          a:     A computer aided design (CAD)package
          b:     A computer game
          c:     A wimp system

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                         Standard Grade Computing
                     Output Devices

1. Monitor / Visual Display Unit (VDU)
     The main output device of a computer,
     used to display text & images. Monitors
     are measured in inches with 15”, 17” and 19” being

2. LCD - Liquid Crystal Display Screens
     Flat screens used in portable computers

3. TFT – Thin Film Transistor Screens.
     Flat screens which are higher resolution
     than LCD but are more expensive.

Both LCD and TFT are used in laptop and palm top
computers, but are also now common on desktop computers.
                                                 Slide 32
   August 2004         Standard Grade Computing
4.        Printers

Laser – A laser beam is used to make an
image of the page on a photosensitive
drum. Toner sticks to the image and is
transferred onto paper. Hot rollers fuse
the toner onto the paper to make the
image permanent. Can be black & white
(mono) or colour.

                     Inkjet – Coloured ink is squirted out
                     of tiny nozzles onto paper to form an
                     image. Inkjets can produce very high
                     resolution images.

 August 2004                                        Slide 33
                       Standard Grade Computing
Summary of Printers

Name             Speed      Resolution          Capital Costs   Running Costs

Laser            10-20ppm   1200 x 1200 dpi Expensive           Low
Inkjet           1-8ppm     4800 x 1200 dpi Cheap £50 -         Very High
Colour           4-20ppm    1200 x 1200 dpi Expensive           High
Laser                                       £500-£4000

   August 2004                                                          Slide 34
                               Standard Grade Computing
5.     Plotters

       A plotter uses a pen to draw the computer output onto
       paper.    There are 2 types:

          (i) Flat bed plotter - the paper is fixed and the pen
               moves in two dimensions.
          (ii) Drum plotter - the pen moves in one direction
               and the paper is moved in the other direction by
               rotation of the drum.

Uses: Computer Aided Design (CAD)

     August 2004                                       Slide 35
                          Standard Grade Computing
6.     Voice output

       A computer can synthesise (make) speech if it has the
              necessary software and loudspeakers.

       Uses: visually impaired & disabled.

                                      The Eclipse system based
                                      on picture/symbol overlays
                                      for input with digitised
                                      speech for output.

     August 2004                                          Slide 36
                         Standard Grade Computing
Virtual Reality

The system creates the illusion that the user is part of the
computer’s world and can move about and manipulate that
  Input devices
      - Gloves fitted with sensors allows wearer to
      manipulate objects.
      - Suits allow people to walk through the virtual world.
      - Headset allows the wearer to look around the
        virtual world.

  Output devices
     - Headset allows a visual output to a pair of small
       screens and sound to a pair of speakers.

  August 2004                                       Slide 37
                      Standard Grade Computing
H         omework   Q  uestions
1.         Name one specialist input device and suggest who might use

2.         Name one specialist output device.

3.         a) Make a list of those input and output devices mentioned
              which you have seen.
           b) Note beside each where you saw it.
           c) How many of them do you think are available in school?

     August 2004                                              Slide 38
                              Standard Grade Computing

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