Hardware

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Hardware
by Hannah Rice
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• Computer hardware is the physical parts of a
  computer- such as the peripherals, motherboard
  and removable media devices ect...

• The processor is the heart of the computer and is
  responsible for all the calculations done on the
  computer.

• The speed of the processor determines how many
  calculations can be done in a second.

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Memory
There are two types of memory, Read Only Memory
(ROM) and Random Access Memory (RAM).
Read Only Memory (ROM)

• ROM memory has instructions which are fixed into
  the computer chip. These could be permanently
  wired into the chip or could be Flash ROM which
  can be written to under certain conditions.

• ROM chips are found on hardware components so
  when they turn on they have the instructions they
  need to work properly.

• One important ROM chip contains the computer
  BIOS. This is a set of instructions which checks
  the computer when it is first switched on, checks
  the memory and communications to the disc drives
  and then loads the operating system. Without the
  BIOS the computer could not even switch on
  properly. It is important then that these
  instructions are not erased when the computer
  switches off.

Random Access Memory (RAM)

• RAM is used to store computer programs and data
  they need and create.

• RAM is said to be volatile, as it needs
  electricity to work. When the computer is
  switched off the contents of RAM are erased.

• RAM can be home to a number of programs and their
  associated data when the computer is running and
  it is up to the operating system to allocate
  enough RAM to each program, so they do not try
  and use the same space.

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Storage 1
Storage devices are used to store programs and
data while the computer is switched off and to
transfer data between machines.
Hard Disk Drive

• These are a series of metal discs onto which data
  is stored magnetically. The discs rotate
  continuously while the computer is on and the
  read/write heads move to transfer data.

• The hard disc is the standard means of storing
  data in the computer.

• They are generally not very moveable as they are
  an integral part of the computer.

• Hard discs need to be formatted before they can
  be used. This divides the disc up into
  addressable tracks and sectors which makes it
  easier for data to be found by the operating
  system.

Floppy Disk

• A flexible plastic disc with a magnetic film is
  encased in a rigid protective cover.

• The advantage of the floppy disc is that it is
  portable and is used to carry data between
  machines.

• The drawback of floppy discs is that they are
  quite an old technology and both the capacity
  (1.4Mb) and the speed of data transfer is now
  making them more suitable for small non-critical
  storage.

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Storage 2
Zip Drive

• Zip drives were designed to over come the
  capacity issues around floppy discs.

• The discs are similar to a floppy disc in that a
  protective casing surrounds a magnetic disc.

• Their capacity ranges from 100Mb to 250Mb

• These discs need a special drive (often
  externally connected to the computer) to allow
  transfer to and from the PC. This is a draw back
  and are usually used just to back-up files.

Compact Disk

• CD's are plastic discs with a fine coating of
  aluminium.

• The data is encoded into the discs using a
  pattern of pits which are read by a laser.

• There are a number of different types of CD's

• CD-ROM - These are read only discs. They are
  commonly used to distribute software.

• CD-R - These are recordable CD's which use a
  laser to create the pits in a blank disc (thus
  writing the data) and can then use another laser
  to read the data just as a normal CD-ROM.

• CD-RW - These discs are similar to CD-R's in that
  a laser can be used to write data to the disc,
  but this can be erased and written again. CD-RW's
  can be used in a similar way to floppy discs but
  need to be formatted before they can be used.
  This means that the discs are not readable in all
  CD drives. This is a drawback.

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Storage 3
Digital Tape

• Digital Audio Tape (DAT) stores data on magnetic
  tape.

• These tapes can have a high capacity and are used
  to back up large volumes of data (such as a whole
  hard disc).

• They are slow to access the stored data as the
  tape needs to be played up to the point at which
  the data is stored.

• Digital Linear Tape is a more advanced (and more
  expensive) than DAT as it has a higher capacity
  and faster access times.

Flash Drives

• Cheap flash memory which needs no power to
  maintain once the data has been written, combined
  with the ease of installation using USB means
  that they are fast becoming the way we store and
  transport data.

• Quicker to use than CDs and a larger capacity
  than floppy discs and Zip discs they are also
  small and compact.

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Peripherals
All the external peripherals need to be connected
to the computer. There are a number of different
sockets that allow these peripherals to connect.
Serial Port

• Also known as COM ports, they attach directly to
  the computers motherboard.

• They transmit data one bit at a time.

• Serial connections are relatively slow because of
  this. Serial ports are used for keyboards, mice
  and external modems.

Parallel Port

• Parallel ports transmit data one byte at a time
  (8 bits together each along their own wire). This
  makes them significantly better than serial
  ports.

• There is a disadvantage in that there is a limit
  to how long a parallel cable can be connecting
  the device to the computer. This distance is
  around 2 metres.

• Parallel ports are commonly used for printers and
  scanners in domestic use.

USB

• Universal Serial Bus is an interface which is
  taking over from both serial and parallel.

• USB supports a wide range of devices, ranging
  from printers, modems, scanners, to digital
  cameras, camcorders and external drives such as
  CD-RWs and hard drives.

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Output Devices 1
Printers
Printers are a common way to get output from a
computer. There are different types of printer,
each with their own advantages and disadvantages.
Dot Matrix

• These have a number of pins (commonly 9 or 24)
  which strike the paper through a printer ribbon
  similar to a typewriter ribbon.

• The pattern of striking pins as the printer head
  moves over the paper determines what is printed.

• The quality of print from Dot matrix printers is
  generally quite poor, the letters looking rough
  as they are made of quite visible dots.

• They are also quite noisy and slow, though they
  are cheap and reliable. They are quite old by
  todays standards but they still have a use.

• When output is printed onto carbonated paper so
  that it prints onto both the top copy and the
  copies underneath (common in forms which are
  partly filled in by computer and then added to by
  people), a dot matrix printer is the best option
  as it is an impact printer.

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Output Devices 2
Ink Jet

• These printers have tiny nozzles filled with ink
  from a cartridge.

• The nozzles are tiny and are heated, causing a
  tiny bubble of ink to touch the paper, thus
  printing.

• The quality of print is much better than dot
  matrix and there are inkjet printers which out
  perform laser printers in their quality of print.

• They are slower than laser printers and do not
  cope well with volume printing.

• Inkjet printers are cheap but become expensive
  when the costs of the cartridges are taken into
  account.

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Output Devices 3
Laser

• A laser and mirror is used to "paint" light on a
  rotating drum.

• The drum is covered by a film of zinc oxide which
  becomes electrically charged by the light.

• The laser is turned on and off to paint the
  correct pattern on the drum.

• The charged areas on the drum pick up black
  powder toner from the print cartridge.

• The toner is deposited on the paper and is fixed
  by heat.

• Laser printers are quick and have a high quality.

• They also perform well when deal with volume
  printing.

• Laser printers are expensive and so are the toner
  cartridges. Each cartridge however does have a
  high capacity.

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Output Devices 4
Plotters

• Plotters are specialised printers which produce
  very precise, high definition output and usually
  are used to produce copies which are A1 or
  larger.

• They are used to create technical printouts such
  as those produced by engineers and architects.

• There are different types of plotter. Some use a
  pen which is controlled by two arms, one moving
  along the x-axis and the other moving along the
  y-axis. There are others with print using and
  ink-jet.

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Output Devices 5
Monitors

• Visual display units (VDU's) are a vital part of
  a computer system, being the primary output
  device.

• There are two main technologies
• cathode ray tubes (CRT)
• liquid crystal displays (LCD).

The screen is made up of small dots, red, green
and blue. These dots are combined to produce a
pixel, which is an addressable unit of the
screen. The number of pixels a monitor displays
is known as its resolution. The higher the
resolution the more detail the screen can
display.
CRT monitors are an older technology, basically
the same as a TV, but with higher definition. LCD
screens are newer and have a number of advantages
over CRTs. They use less energy and do not suffer
from flicker. Large screens are possible with LCD
screens than are possible with CRTs.