Hardware

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Hardware

• www.ICT-Teacher.com

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• Describe the broad characteristics, capabilities
  and limitations of current devices, and
  identifying appropriate contexts for use by each
  device.
• Input,
• Storage,
• Communications,
• Processing,
• Output.

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Hardware

• The physical components of a computer system.
• Input to enter data
• Memory to read the data before processing
• Processor for doing something with the data
• Memory to read the processed data before output
• Output do display the processed data as
  information for us to use
• Storage for storing data for later use when
  requested.

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Processor

• Is the part of the computer that processes of
  data, the arithmetic and logical operations.
• They are measured by their speed of single
  operations in a second, (typically 2 GigaHertz)
  or 2 thousand million a second.
• It controls the transmission of data from input
  to memory, the data forms a queue and is
  processed in order, the data is then transmitted
  back to memory, and then to an output.
• The processor is an integrated circuit and
  contains its own memory, billions of electronic
  components are built onto a small circuit board
  area.

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Main Memory

• The input data and instructions are held in
  memory awaiting processing.
• Memory is measured in bytes (typically 128
  Megabytes), theoretically 128 million characters.
• Memory will contain
• Part of the operation system needed to run the
  application
• Part of the application the user is working on
• The users document s/he is working on
• Other applications that are also open.

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Types of Memory

• Random Access Memory (RAM)
• This is the main memory, anything that is to be
  kept when the work on the application has
  finished, or when the computer is switched off
  has to be stored or lost (volatile).
• Read Only Memory (ROM)
• This is memory needed for the running of the
  computer system and is permanently written onto a
  chip (non volatile). This is most often used to
  locate and start up the operating system when the
  computer is first switched on.

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Processor
Main Memory Random Access
Read Only Memory
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Hard Disk

• Computers contain a hard disk where the operating
  system, the applications software, and files of
  work are stored.
• Storage is measured in bytes (typically 40
  Gigabytes), theoretically 40 thousand million
  characters.
• A hard drive contains many circular storage
  disks, each with their own read/write heads that
  operate independently, to access or store the
  requested file or data.
• The disks spin at high speeds of about 500 times
  a second, this makes the operation fast.
• A hard disk may be removable for secure storage.

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A read / write head on an arm will be able to
access anywhere on the disk
Sectors
Tracks
A Hard drive will have several disks
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Floppy Disk

• Popular for storing and transferring small
  amounts of data or files, typically a few
  letters, or a small presentation, but not
  suitable for high quality images.
• A flexible plastic disk, rotating at 360
  revolutions per second but only when in use, the
  capacity is 1.44 Megabytes.
• Compared to hard disks, access is slower, the
  volume of data stored is much less, and they are
  more prone to damage than the hard disk.
• Advantage portable.

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The floppy disk has two surfaces of 80 circles,
called tracks, each track is divided into sectors.
Formatting means the sectors are ready for use.
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Optical Drives

• CD ROMs, CD-R, CD-RW, DVDs, DVD-RW, are all
  optical devices where data is stored by using a
  beam of light to read from or write to.
• CD ROMs are high capacity of approx 700
  Megabytes, with a transfer rate of 50, (meaning
  50 x 150 kilobytes per second), the writable CDs
  have a much slower write rate.
• DVDs are phasing out the CDs as they are
  capable of storing much greater amounts (24
  times) of data. This capacity is ideal for
  storing a film, or other video / audio /
  multimedia data.

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Hard Disk Drive
Floppy Disk Drive
Optical Disk Drive
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Zip / Jazz Drive / USB Stick

• Zip
• External additional storage, about the same size
  as a floppy drive, but contains much more data,
  approx 100 Megabytes upwards.
• Jazz
• Similar to the zip but has a much larger storage
  capacity, typically 2 Gigabytes.
• The read / write is faster than the hard disk.
• USB Stick
• Small portable stick that plugs into a USB
  socket, typical storage 128Megabytes, very fast.

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Zip Drive
Jazz Drive
USB Memory Stick
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Magnetic Tape

• Magnetic Tape is mainly used as a backup medium.
  It is used for backing up hard discs on both
  microcomputers and mainframes.
• Access times are slow. This is because the data
  is stored in a stream (one bit after the other),
  it takes a while for a
  computer to find
  data if it is in the
  middle or near
  the end
  of a tape.

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Input Devices

• These devices are used to get data into the
  computer.
• There are a variety of input devices, all have
  their own purpose depending on the type of data
  we want to input.
• Many of these devices were discussed on the Data
  Capture slides.
• Examples keyboard, mouse, scanner, digital
  camera, OCR, OMR, MICR, bar code reader.
• Some storage devices are also used for input such
  as data from a floppy disk or a DVD.

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• Keyboard the most popular device, used for
  inputting characters and numbers, good for small
  quantities of input, skilled typists do data
  processing.
• Mouse very popular used for selecting processes
  that include inputting data.

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• Scanner used widely for inserting printed
  material into a computer, most popular are images
  for manipulation or to add to a document.
• The most popular is the flatbed scanner normally
  A4 size for copying from paper and books, other
  scanners are detailed in the Data Capture
  slides.
• Scanners are measured
  in resolution by dots per inch,
  (typically 300 600 dpi).

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• Digital Camera capture an image in digital
  format and can transfer it directly onto the
  computer.
• The camera has storage memory so that a number of
  images may be taken before downloading. Cameras
  are measured in resolution by their maximum
  number of pixels, (typical 4 million).
• There is no developing costs so only the best
  images may be stored, deleting the rest.

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Output Devices

• These devices are used to get the results of the
  processing displayed for the user to read.
• There are a variety of output devices, all have
  their own purpose depending on the type of
  information we want to access.
• Output may be viewed on a screen, or printed on
  paper, or listened to, or sent electronically.
• Examples monitor, printer, plotter, loud
  speaker.
• Some storage devices are also used for storing
  the output such as a floppy disk, or a CD-Writer.

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Monitor

• Monitor the most popular of output devices, much
  information can be displayed on a screen,
  including windows on top of windows.
• They are measured diagonally in inches, popular
  sizes are 14 or 15 but larger ones are used as
  well.
• They are also measured by resolution, the amount
  of pixels (dots of colour) that can be displayed
  a typical example is 1024 x 768.

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Speakers

• Much output from a computer is in the form of
  sound.
• The computer has its own internal speaker from
  which the quality is very poor.
• Using the latest sound card circuit boards and
  loud speakers high quality sound may be
  reproduced.
• The spoken word may be useful to read out the
  contents of a document, music may be played from
  the Internet, and sound on video used for
  displaying films, games, multimedia applications.

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Monitor
Speakers
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Printers

• The next most popular output device is a printer,
  used for hard copies, or for sending to other
  people.
• There are various types of printer
• Laser
• Ink-jet
• Dot-matrix or Impact.
• A Graph Plotter will be used in design offices
  where plans, maps, and 3D building / electronic
  designs are drawn to scale. The printing area is
  larger than the normal sized printer.

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Laser Printer

• Laser printers are similar to the photocopier.
• A laser marks out the image and the toner ink is
  heated and fused to the paper in the pattern of a
  character / an image etc.
• Most laser printers use black toner, but there
  are many more colour printers now being used.
• The results are fast and very high quality.
• These printers are expensive to buy and the toner
  replacements are also expensive.

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Ink-Jet Printer

• Ink-jet printers use a very fine directed spray
  of ink onto the paper in the pattern of a
  character / an image etc.
• Ink-jets use tanks of ink, either just black, or
  for a colour printer three primary colours as
  well.
• These printers are relatively cheap and can be of
  very high quality (photo) when printed onto
  glossy paper.
• The cost of replacement tanks of ink can be high
  as they need replacing often, special paper can
  also be expensive.

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Dot-Matrix Printer

• Dot-matrix printers are similar to the old
  typewriter, where a pin with a character outlined
  on it is fired onto an inked ribbon, which is
  then stamped onto the paper.
• These are the older type of printers, but are
  useful if printing on carbon copy paper.
• They are cheap to buy and cheap to run as the
  only replacement is the inked ribbon. They are
  useful for draft results.
• The output is low quality, slow, the graphics are
  very low resolution, and they are noisy.

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Laser Printer
Ink-Jet Printer
Dot-Matrix Printer
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Communication Devices

• In most organisations computers are linked
  together in a network.
• Data and information may be accessed and shared
  between users without changing computers.
• Network devices need a circuit board inside each
  computer workstation and connecting cable.
• We will discuss networks next week.

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Modems

• A modem is used to convert a digital signal from
  the computer into an analogue signal (sound) for
  transmitting along a telephone network line.
• A modem will also convert the analogue signal
  back into a digital signal for processing inside
  the computer.
• The telephone network is only capable of
  transmitting analogue sound signals.
• Newer networks of high quality wire and fibre
  optics can carry digital signals.
• Modern telephone networks contain a mix of both.

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• Modems generally run at a speed of processing
  56,000 bits per second, but this is much faster
  than the telephone network can take.
• Actual speeds are much slower due to the modem at
  the other end and the quality of the line.
• Modems allow users to send and receive e-mails,
  to access the Internet, and to use voicemail.
• The telephone charges are local call rate, or by
  paying a set monthly rate, longer periods of
  access time are available, such as evenings and
  weekends, or anytime.

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ISDN

• Integrated Service Digital Network is what it
  says Digital.
• The telephone network is used along with special
  newer transmission lines that are digital.
• There is no need for a modem but a special device
  known as a terminal adapter.
• The terminal adapter buffers the data that is
  sent by the computer to relay it at a speed
  suitable for the digital line. It also used
  certain protocols (rules) for transmitting and
  receiving to global standards.
• Data transfer is much faster than modems and is
  suitable for video.

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ADSL

• Asymmetric Digital Subscriber Line is very fast
  and using the most up to date equipment on the
  existing telephone network can produce a data
  transfer rate of up to 40 times the speed of the
  fastest modem

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