ICT Hardware Revision Notes

These notes look at the hardware topic in ICT.

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ICT - Hardware
Software
These are programs that the computer runs.
Programs are stored instructions that tell the computer what to do.
Input devices
These are peripherals that are used to capture data and send it to a
computer system. Whatever data they capture, they have to convert it to
electrical signals. Examples of input devices include:
o Keyboard
o Touch screen
o Mouse
o Keypad
o Microphone
Automated input devices include:
o Barcode reader
o Optical Mark Recognition
o Scanners
o Sensors
o Optical Character Recognition
o Magnetic Ink Character Recognition
Output devices
These are peripherals that pass data back from a process. The output may
be intended for humans to see or for devices to respond to. The VDU (or
monitor) is the most well known output device. Other output devices
include:
o Laser printers
o Ink Jet printers
o Dot Matrix printers
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Storage devices and media
Backing storage is used to keep data or programs.
Different circumstances require different methods.
Backing storage devices are the hardware peripherals used to store data.
These devices write data onto backing storage media and read it back.
Magnetic Discs
Common magnetic disks are hard disks and floppy disks.
They store data by magnetising a special material that coats the surface of
a disk.
When a disk is formatted, magnetic rings are written to the disk, ready to
hold data. Each ring is called a track, and each track is split into sectors.
Data can be written to or read from and track or sector straight away ­
this is called random access.
Hard discs

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Hard discs are usually built into the computer.
The hard disc medium is made of metal and is inside the hard disk drive.
Hard discs hold a lot of data, which can be retrieved very quickly.
Hard discs normally store the computer's operating system, the applications
and the user's data.
Floppy discs
Floppy disks are removable and easy to carry about.
They hold a relatively small amount of data, usually 1.44 Megabytes.
Data on floppy discs is retrieved quite slowly.…read more

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Switches
All data and instructions are stored in a computer in bit patterns.
Every memory location in RAM in a typical computer is made from 8
switches, which can either be on or off.
The state of these switches can be used to code data. A switch being on
or off is the smallest piece of information that a computer can code. It is
called one bit.
Eight bits stored together as a group makes one byte.…read more

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Networks allow tight control over who has access to what data.
Disadvantages
Networks can be expensive to set up, both the hardware infrastructure and
the expertise to create them.
Networks are vulnerable to security problems. Much effort is spent
preventing unauthorised access to data and software.
If a server causes problems, the whole enterprise can be brought to a
standstill.
Because networks are complex, there is a need to employ a network
manager and probably other staff to keep it working properly.…read more

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Advantages
Very fast ­ all data traffic is in the same direction so there should be no
collisions.
Disadvantages
Total dependence upon the one cable ­ if it fails, the whole network goes
down.
Most networks include one or more servers. The other computers are called
clients. The clients make use of services installed on the server, such as file
access and printing.
A star network
Each workstation has its own direct line to the server.…read more

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Extra hardware required such as hubs, switches and wiring centres.
Servers
Servers have more RAM and disc space than clients. This is to allow them to
handle many requests for services more or less at the same time.
Small networks sometimes do not have a server. The clients can share peripherals
and files. These networks, where all the computers are `equal' are called
peer-to-peer.
Network software
Networks have special operating systems. These provide extra services over
stand-alone operating systems.…read more

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Data transfer
Transfer speed
Data transfer is measured in bits per second.
Networks
Networks are sometimes slow to use:
o Software takes a long time to load
o Saving and retrieving data is slow
o Logging on is slow
Many things can affect the performance of a network:
The topology
The capacity of the hardware
The server
The location of the software and files
Transferring images and sound
Images and sound require large amounts of data. To reduce download time,
the files are usually compressed.…read more

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