Standard Grade Computing Studies Computer Systems Frank Frame

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Standard Grade Computing StudiesComputer
SystemsFrank Frame
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Types of Computer System Featured on the DVD

• Mainframe
• A mainframe computer is a computer
• system with
• - very powerful processors
• lots of backing storage
• large internal memory.
• Mainframes are designed to process large volumes
  of data at high speed. They are used by large
  businesses such as banks and mail-order companies
  as well as by large organisations such as
  universities.

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Types of Computer System Featured on the DVD

• Personal computer
• A personal computer (PC) is a computer that is
  small and cheap enough to be owned and/or used by
  a single person.
• Desktop
• A desktop computer is the most common kind of PC.
  It is a collection of a number of different
  hardware devices. This type of computer is sited
  permanently on a desk because its design means it
  cannot be easily moved. The common components of
  a desktop PC are
• the system unit containing the
• processor and main memory
• monitor
• keyboard
• mouse
• hard disk drive
• floppy disk drive
• CD/DVD drive
• speakers.

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• Laptop/notebook
• A laptop computer is a small, light computer that
  you can easily carry about with you. It can be
  powered by battery or mains power. A laptop
  computer has a keyboard, and comes with
  specialised input devices, for example
  trackballs, touchpads or trackpoints. They are
  needed because laptop computers are often
  operated in places where it is impracticable to
  use a mouse.
• For output the laptop has an LCD or TFT screen
  and a set of small speakers.
• Laptops are often as powerful as desktop
  computers and run the same range and type of
  software.
• People use laptops for working when they are on
  the move, going to meetings or attending courses.
• Many businesses are replacing desktop
• PCs with special plug-in workstations
• designed round laptop computers because
• of the flexibility they offer.

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• Palmtop (or PDA) computer
• This type of computer is increasing in
• popularity, and is often called a Personal
• Digital Assistant (PDA).
• A palmtop computer is small enough to fit in your
  pocket.
• It combines a lot of capabilities, including
  organiser features (such as storing contact
  numbers, names and addresses etc.), e-mail and
  wireless internet access.
• Palmtops have small keyboards and most let you
  open menus and select icons by using a special
  pen or stylus. Most let you enter data by writing
  with the stylus. They are powered by batteries
  and store their data on removable memory units
  called flash cards.
• You can run a wide range of software on palmtops,
  for example simple word processing, database and
  spreadsheet software as well as useful
  applications such as electronic diaries. Many
  modern palmtops
• are converging with mobile phones to let you
  access the internet
• have wireless communications to let you access
  your local area network.

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Hardware Devices

• There are three categories of device that can be
  attached to computers we need to know about
• input devices
• output devices
• backing storage devices.
• The use of input devices and output devices are
  quite obvious giving computers instructions and
  displaying results. Backing storage is the
  permanent record of work completed. Files or
  programs saved to these devices can be loaded
  later.

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Input devices

• A large number of different devices are to allow
  users to give information, or input, to the
  computer. Text, numbers, sound, graphics, video,
  movement, heat, touch, etc. can all be entered
  using the correct device.

Output devices

• Output is usually limited to text, sound and
  pictures. Permanent paper copies are produced
  using printers and plotters.
• Printers use different technologies to produce
  paper hard copies (printouts).

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Backing storage

• In recent years backing storage devices have
  increased dramatically in their variety and also
  the amount (capacity) of storage. This has
  dramatically reduced the cost of storage per
  gigabyte1 of information.
• 1 Gigabyte a unit of information equal to one
  billion (1,073,741,824) bytes or 1024 megabytes

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Types of Input Device Featured on DVD
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Trackpad

• Trackpads are found on laptops. The trackpad does
  the job of the mouse and lets you
• control the cursor by dragging your finger across
  the pad
• select items from menus or open up files by
  tapping on the pad.

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Keyboard

• This is the main input device for desktop and
  laptop systems.
• It has keys for
• text entry
• entering numbers
• carrying out special functions such
• as printing the screen display.

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Mouse and trackball

• A mouse is the other standard input device
  supplied with desktop computers. It is a pointing
  device that allows the user to move a pointer or
  cursor across a monitor screen. The mouse is a
  very important input device. It helps you to do
  many things, such as
• controlling the cursor or pointer
• opening up menus
• selecting items from menus by clicking the mouse
  button
• opening up software by clicking the mouse button
• dragging icons to move them into folders, to save
  files.
• Recent changes to improve the functionality of
  mice include cordless mice, optical mice,
  scroll wheels and extra buttons.
• A trackball is like an upside-down mouse. Instead
  of moving the mouse round the desk you move the
  ball you can see in the picture.
• Trackballs were commonly found on laptop or
  notebook computers, but they are sometimes
  replaced with mini-joysticks and trackpads.

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Graphics tablet

• This has a flat surface that can sense the
  slightest touch. Artists and designers use it to
  enter drawings into a computer system. By
  dragging a stylus across the tablet surface you
  can draw freehand and the drawing is entered
  exactly into the computers memory.

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• Digital still camera
• How does it work?
• A digital camera takes a photograph by using
  sensors to capture the light that comes in
  through the lens.
• It then converts the light into binary numbers
  that are recorded on backing storage.
• This digital version of the photograph can then
  be displayed on the small screen that is set into
  the camera.
• A digital camera also has software that lets you
  delete unwanted photos while they are still
  stored in the camera.
• You can connect your camera to your PC and
  transfer your photos across.
• Once they are in the PC you can edit your photos
  further by using a good graphics package.

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• Digital still camera
• What are the key features to look out for in a
  digital camera?
• The number of megapixels the camera has.
• A megapixel is a million pixels. This is a
  measure of how accurately the camera captures
  images. It refers to the number of sensors the
  camera uses to detect the light. The more pixels,
  the better the quality of pictures the camera can
  take.
• The amount of onboard memory the camera has.
• The larger the onboard memory the more photos it
  can store. Camera memory sticks come in various
  sizes.

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Advantages of a digital camera

• It can hold lots of photos without the need to
  buy film.
• You can see what your photo is like straight away
  and you can delete any you do not want.
• The photos are digital so you can transfer them
  to your PC and then do all sorts of things with
  them such as edit, print, store on a writeable
  CD, attach to an e-mail.
• You do not need to have photos developed, saving
  time and money.

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Digital video camera

• How does it work?
• A digital video camera captures moving images
  using technology similar to that used by a still
  digital camera.
• It uses light sensors to capture the images.
• The images are then changed into binary numbers.
• The binary numbers are then stored in files on
  the cameras backing storage.
• What are the key features of a video camera?
• The accuracy of the image sensors used to take
  the film. This is measured by the number of
  pixels that the camera uses to capture the images.

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Backing storage

• This varies in size and type. Some of the latest
  types use DVDs to store their video files. They
  can hold up to two hours of video each or over
  2000 still photos. Once filming is complete the
  DVD can be viewed in a DVD player or transferred
  to a PC for editing.

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The type of display screen available on the camera

• Some have small touch-sensitive screens that
  allow you to make selections and edit your film.
  Others have small eyepieces that you hold up to
  your eye to view what you have just filmed.
• Touch-sensitive screens are display screens that
  are sensitive to the touch of a finger or stylus.
  They are often used with custom-designed
  applications so that the on-screen buttons are
  large enough to be pressed with the finger.
  Applications are typically very specialised and
  greatly simplified so they can be used by anyone.
  However, touch-sensitive screens are also very
  popular on Personal Digital Assistants (PDAs) and
  full-sized computers with standard applications,
  where a stylus is required for precise
  interaction with screen objects.

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The onboard editing features

• The software that comes with the camera can be
  quite powerful offering the user a whole range of
  features such as
• focus
• adjustable lighting
• infrared
• zoom
• special effects.

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Webcam

• This is a digital camera that is used to take
  photos and then send them across the internet.
  Webcams capture and transmit still photographs
  that can be updated at various speeds, from one
  frame every few minutes, to full streaming video,
  depending on the speed of the computer system and
  the software settings.
• The technology for capturing the images is
  similar to that used in the other digital
  cameras.
• The difference is that once an image is captured
  it is transmitted automatically to a computer
  system. Webcam software in the computer system
  then transfers it to a web page.

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Webcam

• What are webcams used for?
• They are used for a wide range of purposes some
  examples are to
• set up videoconferencing
• monitor traffic
• advertise tourist sites

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Types of Output Device Featured on DVD
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Printer

• Printer
• Computers were supposed to bring about the dream
  of a paperless office. This now looks very
  unlikely to happen because paper has got some
  advantages over computers when looking at
  information.
• It is very portable. The information on a sheet
  of paper is easily passed around, and many people
  can look at the information at the same time.
• It is cheap. Initial costs of computers means
  there is no comparison with the cost of using
  paper.
• Not everyone has computer equipment to view
  information, or it may be difficult to use
  computers in some situations.
• Paper copies, or hard copies, of information will
  always be needed. Printers (and plotters) are
  used to produce these hard copies. The main
  different types of printer, and how they are
  compared against each other, are explained below.

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Laser printer

• This type of printer is the main one used in
  schools, offices and industry because it produces
  high-quality printouts very quickly, with good
  resolution. It uses a laser to make a negative
  electrical image of the page on a positively
  charged drum, which then picks up positively
  charged toner. The drum rolls over the paper and
  the toner is heated to print on to the page. The
  toner cartridge gives many copies before needing
  replaced keeping running costs down.
• While it is the most expensive to buy, especially
  for colour, the price of this printer has fallen
  dramatically.
• Laser printers are generally more expensive than
  inkjet printers, but their running costs are
  lower.

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Inkjet printer

• Basic models of this type of printer are cheap to
  buy, and let you print in colour. The quality of
  the best inkjets can be very high and can be used
  for photographs.
• Inkjet printers spray special ink on the paper to
  form characters and graphics.
• The cost of replacing ink cartridges can be high
  with this type of printer because they need
  replaced frequently. They print quite quickly,
  but can be quite slow when printing graphics.
• They are slower than laser printers.

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Comparing printers

• When we compare printers we should look at the
  following characteristics.
• Set-up costs
• This is a little tricky because it seems at first
  that inkjet printers are really cheap. The
  initial cost or capital cost can be very low with
  a new inkjet printer costing as little as 60.
  This is not the whole story because inkjets can
  have expensive running costs.
• Running costs
• After you buy a printer these other costs become
  important. Consumables (ink refills, toner for
  laser printers, special paper) need to be bought
  regularly and the cost of these varies from
  printer to printer. Colour inkjet cartridges can
  be very expensive at around 20 each. Depending
  on how much printing you do you can soon end up
  paying more for the ink than the printer itself!
• The cost of repairs may also need to be
  considered for expensive printers.

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Comparing printers

• Resolution
• Resolution is measured in dots per inch
  (shortened to dpi). This is used to measure the
  quality of the printout. Let us take the example
  of a resolution of 300 dots per inch. That means
  that for each square inch there are 300 x 300
  dots 90,000 dots. The higher the number of dots
  per inch the sharper and clearer the image will
  be.
• Speed
• We should look at how long they take to print a
  page. Different printers have different printing
  speeds. Measured in pages per minute (ppm),
  faster printers are normally more expensive and
  are often networked to allow many users to take
  advantage of the speed.

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Comparison table
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LCD (liquid-crystal display)

• These screens are flat, need only a small amount
  of power to run and can be powered by batteries.
  They do not weigh as much as ordinary monitors.
  This means they are ideal for use on laptops and
  palmtops. Liquid crystals work by blocking light
  reflected from behind, so the screens cannot be
  read in the dark unless they are backlit.

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TFT (thin-film transistor)

• TFT is a type of LCD screen that has more complex
  electronics than an ordinary passive LCD. It uses
  arrays of transistors to control backlighting of
  the screen actively. These enable it to display
  graphics and animations much more clearly and
  quickly than an ordinary LCD and can display
  moving graphics without shadowing.

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SOUND CARD

• A sound card captures sounds and changes them
  into digital form patterns of binary numbers
  that are stored as files in your computer.
• When outputting sounds the sound card reverses
  the process and changes the binary data held in
  the sound files into analogue signals that are
  used to control the speakers attached to the
  computer. Speakers convert analogue audio signals
  into the equivalent air vibrations in order to
  make audible sound. A pair of speakers plugs into
  the computers sound card.

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More about capturing sound files

• A microphone can be used to input sound. It
  converts sound waves into analogue electrical
  waves. Usually called a mike, it contains a
  flexible diaphragm composed of film or foil that
  vibrates as it makes contact with sound.
• When capturing music, for example, a sound card
  takes thousands of samples of the sound waves
  each second, turns the samples into patterns of
  binary numbers and then stores them in files.
• The process of taking thousands of samples and
  turning them into binary numbers is very
  demanding on the main processor.
• For example, if a system is sampling at the
  standard rate of 44.1 Khz and each sample is
  stored as a 16-bit binary number then the
  processor has to convert and store 441,000 16-bit
  binary numbers each second.
• To make it easier for the system, a sound card
  has its own processor that relieves the
  computers main processor of all of this extra
  work, which would slow it down.

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Graphics card

• Todays applications use a lot of graphics. Even
  standard applications such as spreadsheets run on
  operating systems with WIMP HCI. This means that
  all applications need graphical items to run,
  such as windows, icons and drop-down menus.
• We also use multimedia and presentation software
  that incorporate graphics, animations and even
  video.
• Gaming software makes the heaviest demands on the
  graphics facilities of our computers with its use
  of three-dimensional graphics and realistic
  animations.
• Graphics cards are designed to support the need
  for increasingly complex. graphics. Like sound
  cards, graphics cards have their own processor
  dedicated to producing the graphics and relieving
  the main system processor of the job.
• Graphics cards also have their own memory
  dedicated to handling the graphic data, relieving
  the pressure on the systems main memory. The
  processor loads in the graphic file, which is
  made up of binary numbers, and then outputs the
  graphic as a stream of signals to control the
  output on the monitor.

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Types of Backing Storage Featured on DVD
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• Backing storage devices are hardware that is used
  to store the programs and data that the computer
  can access. Unlike RAM (or working) memory the
  contents of backing storage will not be lost when
  power to the computer system is turned off.
• The three types of backing storage hardware we
  need to know are
• magnetic drive
• hard disk drive
• floppy disk drive
• magnetic tape drive
• optical drive
• CD drive (ROM and RW)
• DVD drive (ROM and RW)
• flash drive.

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Hard disk drive

• This is a type of magnetic backing storage. This
  means, as with a floppy disk drive, it uses
  magnetism to encode and store data. Hard drives
  consist of stacks of non-removable platters
  coated with magnetic materials each with its
  own read/write head. Hard disk drives are built
  into desktops and laptops.

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Hard disk drive

• The key features of hard disk drives are
• They read and write data very quickly.
• They can hold large quantities of data.
• The capacity of a hard disk is measured in
  gigabytes. It holds much more data than a CD-ROM.
  The capacity of a CD-ROM is measured in
  megabytes. To find the capacity of the latest
  hard drive you should look in the latest computer
  magazines or search the internet.
• Hard disk drives use random/direct access to
  locate data stored on the disk.

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Magnetic tape drive

• This storage device is mostly used for backups
  because, although tape can store a lot of data,
  it is slower to access. Having to wind through
  the tape when finding files, would make it
  impracticable to use as the main storage device.

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CD-ROM

• CD-ROM stands for Compact Disk Read-Only Memory.
• CD-ROM drives use a combination of lasers and
  sensors to read the data stored on the surface of
  the disks. Like hard disk drives they use
  direct/random access to read data.
• CD-ROMs are read-only devices. They can hold in
  the region of 700 megabytes of data.

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DVD-ROM

• DVD-ROM stands for Digital Versatile Disk Read
  Only Memory.
• A DVD-ROM drive is similar to a CD-ROM drive in
  that it uses a combination of lasers and sensors
  to read the data. DVD-ROMs are also read only.

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DVD-ROM

• How are they different?
• A DVD-ROM can store much more data than a CD-ROM.
  A single-sided single-layer DVD-ROM can hold 4.7
  gigabytes. There are double-sided DVD-ROMs with
  several layers that can store up to 17 gigabytes.
• What are they used for?
• DVDs are mainly used for storing movies because
  the files needed to encode a movie are very large
  indeed and are measured in gigabytes.

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CD-Recordable (CD-R)

• This is a CD similar to a CD-ROM. The difference
  is you can store data on the CD-R. Standard CD-R
  disks hold 700 megabytes.
• Using a laser and special dye in the disk a
  CD-Rewriter drive can store your data on the CD.
  Once the data has been burned on to the disk you
  cannot change it, it is read only.

CD-Rewriteable (CD-RW)

• Like CD-R, these are compact disks on which you
  can store data using a CD-Rewriter drive. The
  main difference is that you can change the data
  later on if you want to, just as you can on a
  hard disk.

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DVD-Recordable (DVD-R/DVDR)2

• These are DVD disks that you can write to by
  using a DVD-Rewriter drive.
• 2 DVD-RW and DVDRW are slightly different
  formats, but most new DVD-Rewriter drives can
  handle both types.

DVD-Rewriteable (DVD-RW/ DVDRW)

• These are DVD disks that you can store data on
  over and over again, with a DVD-Rewriter drive.
  They use similar laser technology to CD-RW
  whereby the reflective properties of the disk are
  altered to represent binary numbers.

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DVD capacity
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USB backing storage devices

• There is now a wide range of new storage devices
  that plug straight into the USB port on
  computers. They can store from 8 MB up to
  (currently) 2 GB of data, and are a simple and
  convenient way of backing up or transferring data.

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Comparison of backing storage
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Sequential access to data

• Sequential access means starting at the beginning
  of a sequence of data and going through it one
  part after another until the computer finds the
  data it is looking for.
• A magnetic tape drive, often used for backing
  storage, is the best example of sequential
  access. It starts at the beginning of the tape
  and has to wind forward through the tape until it
  reaches the part it needs.
• This takes time and is not suitable for many
  computer applications that demand fast access to
  data.

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Random or direct access

• Hard disk drives, floppy drives, CD-ROM and DVD
  drives use direct or random access. This means
  they go straight to the data they need. Unlike
  sequential access tape drives, they do not have
  to go through all of the disk surface one part
  after another to find the data.
• Because it gives instant access to the data,
  direct or random access is used by computer
  systems that need to process data straight away,
  unlike sequential access, which takes time to go
  through all the data in the sequence.
• Examples of use updating bank accounts as money
  is taken out of a cash point machine, booking
  seats on a plane.

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Questions and Tasks

• Why do large businesses such as banks use
  mainframe computers?
• Describe the components of the desktop computer
  you use in school or at home.
• Complete this table comparing a desktop with a
  laptop.

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Questions and Tasks

• Name three types of software that run on
  palmtops.
• Why are palmtops useful?
• What is the typical capacity of a CD-ROM?
• What are CD-ROMs used for?
• What is the typical capacity of a DVD-ROM?
• Why are DVD-ROMs used to store videos?
• (a) What do CD-R and DVD-/R have in common?
• (b) In what way are they different?
• 11. (a) What do DVD-/RW and CD-RW have in
  common?
• (b) In what way are they different?
• 12. Complete this table comparing laser printers
  to inkjet printers. You may have to search the
  internet to find out the relevant information.

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• Complete this table comparing laser printers to
  inkjet printers. You may have to search the
  internet to find out the relevant information.

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Questions and Tasks

• What is the difference between an LCD screen and
  a TFT screen?
• What features of LCD/TFT screens make them
  suitable for use on laptops?
• Why is a trackpad suitable for controlling the
  pointer on a laptop?
• Why do you think the combination of a keyboard
  and mouse is used as a means of inputting data
  into a desktop?
• Describe a graphics tablet.
• Who uses a graphics tablet?
• How does a digital still camera work?
• List four advantages of digital cameras.

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Use the internet or the latest magazines to get
information on four of the best digital cameras
and then complete the following table.
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Use a search engine to find a list of webcam
sites and check some out for yourself, then
complete the following table.
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Questions and Tasks

• What is the difference between sequential and
  random/direct access to data?
• Which types of backing storage uses random/direct
  access to data?
• How does a sound card capture sounds?
• Search for two sound cards on the internet or in
  a computing magazine and write up a short report
  on each one.
• Why do computers need graphics cards?
• Why do graphics cards have their own processor
  and memory?
• Use the internet to search for graphics cards.
  Pick two and write a short report on their main
  features.