Computer basics by huanghengdong


									Introduction(Parts of a computer)
Computer Systems are made up of many different parts, for example hardware,
software, processors, memory etc.

Hardware is any physical part of the computer that you can touch, see and

Examples of hardware include the monitor, keyboard, mouse, disk drives, printer,
scanner and speakers.

Software are the applications and programming instructions needed to make the
computer hardware do useful work.

Some examples of systems software which tells the computer what to do:

      Operating System
      Utilities
      User Interface

Some examples of application software which allow you to do your work:

      Word processors such as Microsoft Word
      Spreadsheets such as Microsoft Excel
      Databases such as Microsoft Access

A peripheral is any device which connects to the computer and exchanges data
with the CPU.

Peripherals include all of the computer's input and output devices.

Examples are:

      monitor
      keyboard
      mouse
      printer
      scanner
      speakers
      external hard drives

Central Processing Unit (CPU)
The CPU is the 'brain' of the computer. It is where all the searching, sorting,
calculating and decision making takes place.

The CPU contains a tiny quartz clock. Each time this clock 'ticks', one instruction can be
dealt with by the CPU. So the more times this clock ticks per second, the more
instructions the CPU can carry out and the faster things get done.

The speed of the CPU is measured in either Megaherts (MHz) or more commonly now
in Gigahertz (GHz). A 1 MHz CPU can carry out one million instructions per second. A 1
GHz CPU can carry out 1 billion instructions per second!

A typical CPU installed in a computer today would run at around 3 GHz.

CPU Components
You need to have a basic understanding of the three main parts of a CPU. These
are the:

      Control Unit
      Immediate Access Store
      Arithmetic and Logic Unit (ALU)

The Motherboard is the central circuit board of your computer. All of the
components and peripherals plug into it.

The motherboard houses the ROM chips which store the BIOS instructions (see the
'storage devices' miniwebsite). RAM chips, the CPU, the graphics card, sound card,
network interface card, hard disk and various other external ports and peripherals all
attach directly to it.

The job of the motherboard is to relay information between the components and

Disk Drives
The purpose of a disk drive is to read data from a storage device. Common disk drives
that you will come across in your studies are:

      hard disk drive
      removable hard disk drive
      floppy disk drive
      zip disk drive
      CD drive
      DVD drive

The hard disk drive is installed inside your computer and it reads data stored on the
hard disk.

The floppy, CD and DVD disk drives are installed inside the front of your computer case
so that you can load the disks directly into them.

A zip disk drive and a removable hard disk drive are external to the computer and need
to be plugged in via a USB port.

The two main types of memory that you need to clearly understand are Random Access
Memory (RAM) and Read Only Memory (ROM)

Read Only Memory (ROM)

Data stored on ROM is not erased when the power is switched off - it is
permanent. This is called 'non volatile memory'.

The ROM chip is used to hold data that cannot be changed by the user.
Instructions related to the operating system are stored on ROM chips when the
computer is manufactured.

This data will usually be the software that tells the computer how to load the operating
system when it is switched on or re-booted.

Random Access Memory (RAM)

RAM is volatile memory. The data is held on a chip, but only temporarily. The data
disappears if the power is switched off.

Have you ever forgotten to save your work before the computer crashed? When you log
back on, your work has disappeared. This is because it was stored in RAM and was
erased when the PC was switched off.

However, if you had saved your work, it would have been transferred from RAM to the
hard disk where it would have been stored safely.

Introduction (Input devices)
An input device is a piece of hardware that is used to enter data into a computer.

The keyboard is the most common and widely used input device. It is used to

enter text.

It is made up of buttons called 'keys'. The keys are arranged into sections:

      alphabet keys
      Function or F keys (F1, F2, F3)
      Numeric keys (one set above the alphabet keys and a numeric keypad on the
      Arrow keys
      Command keys (insert, delete, home, end, page up/down)

Most keyboards are called 'QWERTY' keyboards. This name comes from the first six
letters on the top row of the alphabet keys.

                                      Using a keyboard for too long can lead to
health problems such as repetitive strain injury (RSI). To try to overcome this,

different styles of keyboard have been developed, for example, the ergonomic
keyboard. They are supposed to put your hands into a much more natural position than
a traditional keyboard.


      Most computers come with a keyboard supplied
      People are used to using keyboards to enter data, they need very little training
      A skilled typist can enter data very quickly
      Specialist keyboards are available e.g. ergonomic, gaming keyboards


      It is easy to make mistakes when typing in data
      If you can't touch type, it can be time consuming to enter data
      Keyboards are not suitable for creating diagrams
      Disabled people often find keyboards difficult to use
      Excessive use can lead to R.S.I.

Everyone is familiar with a computer mouse; along with the keyboard, it is one of
the most common input devices you will use.

A mouse is also called a 'pointing device' because it enables you to control what
happens on the screen by moving the mouse on your desk and pointing, clicking
and selecting items on the screen.

      Ideal for use with desktop computers
      Usually supplied as part of a new computer system
      Most computer users are familiar with them and require little training
      Works well in conjunction with a keyboard for data entry


      They need a flat space close to the computer

      The rollers in mice that use balls can become clogged with grease and grime and lose
       their accuracy until cleaned.
      Overuse can lead to RSI

Joysticks were originally used by pilots as part of an aeroplane's controls and the
technology was developed to let computer gamers experience a more realistic
game environment.

You can move joysticks in many directions and the joystick tells the computer which
direction it has been moved into. They also have one or more buttons whose position
when pushed can be read by the computer.

Joysticks can also be used for controlling machines such as cranes, trucks and
powered wheelchairs.

      They give a better gaming experience for racing or flying styles of computer


      Some people find joysticks more difficult to control than a traditional mouse.
      Joysticks are not particularly robust and can break easily if too much force is used on


A microphone can be used to input sound.

The sound is detected by the microphone and an electrical signal is transmitted to the
computer. Special hardware is used to convert this analogue data into digital data so it
can be stored and manipulated.

In the last few years a number of voice recognition systems have been developed.
These packages let the user dictate the text into a computer and then convert the
speech to text.

Dictating like this can be much quicker than typing but the software isn't perfect and it
can interpret a word incorrectly.

Scanners can be used to convert images or text on paper into a digital format that
can be used by the computer.

There are two types of scanner:

      Flatbed scanners
      Handheld scanners

                                 The most popular type is the flatbed scanner. This is
probably the one that you use at school. They can scan larger images and are more
accurate than handheld scanners.

Handheld scanners are usually only a few inches wide and are held in the hand whilst
they are rolled across the document to be scanned. The images produced are generally
not as large or as high quality as those captured with a flatbed scanner.


      Flatbed scanners are very accurate and can produce reasonably high quality images
      Any image which is digitised by the scanner can then be included on electronic
      Images once digitised can be enhanced with a graphics application


      Images can take up a lot of memory space
      Images lose some quality in the scanning and digitising process
      The quality of the final image is dependent on the quality of the original image

A bar code is a set of parallel printed lines of differing thicknesses which are used to store
coded information about an item.

Bar codes are read using a Bar Code Reader, which can be in the form of a hand-held ‘wand’
or a stationary laser scanner over which the bar code is passed.

This method of data entry is used in big shops and supermarkets and in libraries.


      a fast method of data entry

      eliminates possible human error


      scratched or crumpled barcodes may cause problems

Introduction(output devices)

2. Monitors
A monitor (or screen) is the most commonly used output device.

They come in many different shapes, sizes and forms. In an exam question, you will
need to be able to choose the best type of monitor and then explain your reasons.

The picture on a monitor is made up of thousands of tiny coloured dots called
pixels. The quality and detail of the picture depends on the number of pixels that
the monitor can display. The higher the number of pixels, the better quality the

Larger monitors make working at the computer much easier on the eyes, but the larger
the monitor, the more money it costs! Typical monitor sizes are 19 inches.

The two types of monitor that you need to know about are Cathode Ray Tube monitors
(CRT) and Thin Film Transistor monitors (TFTs).

Cathode Ray Tube

CRT monitors are becoming outdated, although you will probably remember using them
at school not very long ago.

They are large and bulky and have a glass screen which makes them fairly robust and
difficult to damage.

They produce quite a lot of heat so when you have an office with lots of them it could
get quite warm. They are also fairly noisy compared to newer TFT monitors.

Thin Film Transistor

                                     TFT monitors used to be very expensive but now
the price has come down they are beginning to replace all of the old CRT monitors. Not
only do they look much nicer they take up a lot less space. They are quieter than CRT
monitors and also create less heat.

On the down side they are easier to damage than CRT screens. A few sharp pokes at
the screen with a pencil can cause lasting damage. Another disadvantage is that unless
you have a very high quality TFT monitor, the colours and contrast are not so good as a
CRT monitor and so the picture can look a bit dull.

3. Printers
Printers are another common output device. They are used to create a 'hard' copy
of your work i.e. something that you can hold, hand to someone else or file away.

Most printers produce their output on paper

However, paper isn't the only thing that you can print things onto:

4. Laser Printer
Laser printers are used in many workplaces because they are quiet, they print a large

number of                                                  sheets very quickly and they
produce high quality documents.

They print in the same way as photocopiers. Powdered ink, called 'Toner', is fused onto
paper by heat and pressure.

You can purchase a laser printer which prints black and white copies only or you can
pick a colour laser printer. Black and white versions are relatively cheap to purchase
and you only need to buy one toner (which is also expensive). Colour laser printers are
still a little too expensive for most people to purchase for home use although many
offices now have at least one colour laser printer.

      High quality printouts - better than ink-jet or dot-matrix
      Fast printouts - faster than ink-jet or dot-matrix
      Prints very quietly - quieter than ink-jet or dot-matrix
      Cost per page is low - cheaper than ink-jet or dot-matrix


      Most expensive printer type to buy, especially colour lasers
      Toner is more expensive than ink-jet cartridges
      Expensive to repair - lots of complex equipment inside
      Fairly bulky - larger than ink-jet printers
      Can't use continuous or multi-part stationary to create carbon copies like you can with a
       dot-matrix printer

5. Ink-Jet Printer
Ink-jet printers have been popular for a long time because they are relatively cheap to
buy and most of them can combine both black and white and colour printing at the same

These printers use cartridges which contain ink. They operate by heating the ink as it
flows through the nozzle. The heating process causes a small droplet of ink to form.
This is then released as a single dot which forms part of a letter or image. This is why
the printouts often come out of an ink-jet printer still slightly wet.

Colour ink-jet printers are ideal for use at home where only a few documents need to be
printed and the quality of the printout doesn't need to be perfect.

      Cheap to buy - cheaper than a laser printer
      More compact than a laser printer
      Cartridges cost less to replace than toners
      Produce good quality printouts better than a dot-matrix but not as good as a laser
      Speed - faster than a dot-matrix but not as fast as a laser


      Noisier than a laser printer (but not as noisy as a dot-matrix)
      Colour printing can be extremely slow
      Cost of printouts per page are more expensive than a laser printer
      Cartridges need to be replaced more often than a laser printer
      Ink will smudge while it is still wet
      Colours can become saturated and often don't look the same as on the screen
      If not used for a while, the cartridges can dry out

. Dot-Matrix Printer
These were the first type of printers to be used in homes and schools but they are not
used much nowadays.

They are also called 'impact printers'. The print head contains a grid of pins and
different combinations of pins are pushed out to form different characters. The print
head then hits a carbon ribbon leaving an imprint on the paper. This makes them fairly
noisy as you can hear the pins striking the paper.

Dot-matrix printers are ideal when you need carbon copies. This is because the print
head hits the paper with enough force that when carbonised paper is used, the impact
makes a copy on the second sheet.

They are also useful when continuous paper needs to be used for example printing
large quantities of invoices or bills. They can be printed onto paper with perforations and
then separated by tearing once the printing is complete.

      Relatively cheap to buy
      Low operating costs
      Can print on continuous stationary
      Create carbon copies using carbonated paper
      Robust and will work perfectly well in harsh or dirty conditions such as garages or


      Print quality is poor and important documents are not suitable to give to managers or
      Very slow - slowest out of all three printers
      Noisy - you wouldn't want one of these printing all day in the office
      Cannot produce colour copies

7. Plotter
Plotters are a specialist type of printer which is able to draw high quality images
on very large pieces of paper, for example 3 foot wide by 10 foot long.

They are used by engineers, architects and map-makers to draw plans of
buildings, diagrams of machines or large scale maps. They can also be used for
many other similar tasks.

A plotter differs from a printer in that it draws images using a pen that can be lowered,
raised and moved across the paper to form continuous lines. The electronically
controlled pen is moved around the paper by computer controlled motors.

There are plotters now which are 'pen-less'. these are used for creating high density

drawings such as the one shown in the image above.

There are three different types of plotter:

Flatbed plotters - These hold the paper still while the pens move

Drum plotters - These roll the paper over a cylinder

Pinch-roller plotters - These are a mixture of the two types above


      Drawings are of the same quality as if an expert drew them
      Larger sizes of paper can be used than most printers can manage


      Plotters are slower than printers because each line is drawn separately
      They are often more expensive than printers
      They do not produce very high quality text printouts

Most computers are fitted with a small internal speaker which can produce beeping
sounds to alert you if you make an error.

Computers can also be fitted with a sound card (or chip) which will enable sound to be
output through external speakers. These usually produce a much higher quality sound
than the internal speaker.

      Everyone in the room can hear the output from the computer.
      They can help create an atmosphere or ambiance to accompany a presentation

      They help blind people to use the computer because text can be converted into sound


      The output from speakers can disturb others who are trying to work
      High quality external speakers can be expensive

Introduction(storage devices)
Unless you want to lose all of the work you have done on your computer, you need to
have a way to store it safely.

There are various types of storage devices, different devices are suitable for different

We will be looking at the main ones which you need to know about. Just work your way
through the pages by clicking on the left hand menu.

2. Storage Capacity
Data can be stored either in the 'internal memory' or on a 'storage device'.

The amount of data and instructions that can be stored is measured in 'bytes'.

One byte contains 8 bits (short for Binary Digit). This is the smallest unit of data that can
be stored. Each 'bit' is represented as a binary number, either 1 or 0.

A single keyboard character such as the letter A or T takes one byte of storage.

We normally refer to the capacity of a storage device in terms of Kilobytes (KB),
Megabytes (MB), Gigabytes (GB) - or even Terabytes!

 Storage sizes
Quantity               Information

Bit                    Smallest unit of data, either a 0 or 1

Byte                   8 bits

Kilobyte (Kb)          Assumed to be 1,000 bytes. In reality, it is really 1,024 bytes.

Megabyte (Mb)          1,000 kilobytes (1,024 Kb)

Gigabyte (Gb)          1,000 megabytes (1,024 Mb)

3. Read Only Memory (ROM)

ROM is a special kind of memory which stores the instructions which the computer uses

when it                             'boots up' - the BIOS (basic input output system). It
allows it to check the type of hard disk installed, the amount of RAM installed (see next
page), the type of CPU being used etc.

Because the data is 'read only', it can be read but not changed by the user.

                           The ROM chip (although there may be more than one) is
attached to the Motherboard.

The key thing to remember about ROM is that the data is not erased when the computer
is switched off - the data is stored permanently. This type of memory is called 'non
volatile memory'

4. Random Access Memory (RAM)
How many times have you worked for a whole lesson on something which you were just

about to                                     save but then the computer crashed or your
mate 'accidentally' switched it off. When you rebooted and logged back in, your work
was gone forever.

This was because your work was stored in RAM, or 'temporary memory'. It was fairly
safe there while the computer was working, but as soon as it was switched off,
everything disappeared. This type of memory known as 'volatile memory'.

As well as storing the data you are working on, RAM also stores the modules that are
needed to make your applications work. For example, when you open up Microsoft
Word, you may notice a short delay while the modules are loaded into RAM.

RAM is also needed so that you can have multiple windows open and so that you can
switch between them.

However, if you have a lot of windows, documents and different applications running,
you might find that your system starts to slow down. This is because your RAM is full up
and it is having to decide what it needs to keep stored in memory at any given time and
what it can release. If this happens to you a lot, you can improve the performance of
your computer by installing extra RAM.

Most computers are typically sold with 1-2 Gb of RAM installed.

5. Hard Disk

The hard disk is the main storage device in your computer. It is a bit like a filing
cabinet: all of your data files and applications software are stored on it.

The hard disk contains a number of metal platters which have been coated with a
special magnetic material. The data is stored in this magnetic material. Thus, the hard
disk is known as a magnetic storage device.

      necessary to support the way your computer works
      large storage capacity
      stores and retrieves data much faster than a floppy disk or CD/DVD
      Stored items are not lost when you switch off the computer

      Cheap on a cost per megabyte compared to other storage devices


      Far slower to access data than ROM or RAM chips
      Hard disks can crash which stop the computer from working
      Regular crashes can damage the surface of the disk, leading to loss of data in that
      The disk is fixed inside the computer and cannot easily be transferred to another

6. Floppy Disk
Floppy disks are one of the oldest types of portable storage devices still in use,
having been around since the 1980s. However, they are gradually becoming obsolete
and some manufacturers are now starting to build their PCs without floppy disk drives.

A floppy disk can store up to 1.44 Mb of data which is equivalent to around 300
pages of A4 text. They used to be the ideal storage device for transferring small files
from home to work/school or from one office computer to another. But nowdays, many
files contain graphics or WordArt and are larger than the size of the floppy disk.

Floppy disks are a magnetic storage device.

All disks must be formatted before data can be written to the disk. Formatting divides
the disk up into sections or sectors onto which data files are stored. In the past, the user
would have to format their own disks, but now they are sold pre-formatted.


      Portable - small and lightweight

      Inexpensive
      Useful for transferring small files between home and school
      Security tab to stop data from being written over
      Can be used many times


      Not very strong - easy to damage
      Data can be erased if the disk comes into contact with a magnetic field
      Quite slow to access and retrieve data when compared to a hard disk
      Can transport viruses from one machine to another
      Small storage capacity
      Many new computers don't have floppy disk drives

Compact Disks (CD)
Compact Disks come in three main forms:

CD-ROM - CD Read Only Memory. This means that when you buy the disk, it already
has the data or program stored on it. You can read it, but can't save to it. An example
would be a music CD that you buy from a shop.

CD-WORM - CD Write Once Read Many. This means that you are able to save to this
disk one time, so you can store your data or an application on it of your choice.
However, once you have saved onto the disk once, you can access the data many
times but can't save onto it again.

CD-RW - CD Read Write. This means that you can save data to your disk over and over
again, just like you can with a floppy disk.

Compact disks are known as optical storage devices. Data is burned onto the
surface of the disk using a laser beam in the CD drive. A laser beam is also used to
read the data stored on the disk.

A typical CD can store around 700 Mb of data - equivalent to 450 floppy disks. The
entire contents of four text based encyclopedias (no images) could be stored on a single

      Small and portable
      Very cheap to produce
      Most computers can read CDs. If there is no CD drive, a DVD drive can usually read
      Fairly fast to access the data - quicker than a floppy disk or magnetic tape


      Fairly fragile, easy to snap or scratch
      Smaller storage capacity than a hard drive or DVD
      Slower to access than the hard disk.

10. Digital Versatile Disk (DVD)
DVDs are amongst the most common methods of copying and backing up data at

A DVD is similar to a CD in that it is an optical device and that a laser is used to
store the data and read the data.

A single sided DVD can store about 4.7Gb of data. DVDs which store data on both
sides can hold over 9Gb of data.

You will see various kinds of DVD disks for sale: DVD-R, DVD+R, DVD-RW and


      Very large storage capacity
      Sound and picture quality is excellent, making them ideal for storing films with video and
      DVDs are now mass produced so they are relatively cheap
      DVD players can read CDs


      DVDs do not work in CD drives
      There is no single standard of DVD
      They can be easily damaged by breaking or scratching

11. Flash Memory
Flash memory storage devices are typically small, lightweight, removable and
rewritable. They consist of a small printed circuit board which is encased in plastic or
metal casing. They usually have a removable cap which covers and protects the part of
the stick which is inserted into a USB port.

Memory sticks are available from 1 Gb up to 16 Gb.

      They are more compact and portable than floppy disks or CDs/DVDs.
      They hold more data than a floppy disk and nowadays often more than a CD.
      They are more reliable than a floppy disk because they have no moving parts

      They are being developed with fashionable looking outer casings and are almost
       becoming a 'fashion accessory' much in the way of a mobile phone.


      At the moment, the cost per megabyte of storage is more expensive than floppy disks,
       CDs or DVDs.
      They can be easily lost
      The metal part which is inserted into the USB port can be snapped off if they are
       handled roughly

Introduction (Types of computers)
There are many different types of computer available today. They range from giant
super computers right down to small hand-held personal organisers.

Supercomputers are the fastest and most expensive computers in the World.

They can cost over a hundred million pounds to build and very few organisations
can afford to purchase one.

They are mainly used by large universities who do a lot of research projects such
as scientific research, weather modelling etc and by large organisations such as
pharmaceutical companies for drug research or by the military for weapons

Whilst supercomputers are working, they generate so much heat that they need to be
housed in specifically designed rooms with environmental controls and air conditioning
systems. It is vital that the atmosphere is kept free of dust particles and special filters
are used to keep the air clean.

There may be many miles of cables which connect the computer to various peripherals.
In order to hide the cables, false floors and ceilings are often needed.

Supercomputers usually need their own back up electricity generator to ensure that they
can continue to work even when there is a power failure.

3. Mainframe Computers
Mainframes are large, powerful computers that can carry out many different tasks
for many different people at the same time.

They are slower than a supercomputer but they are far less expensive. They may
cost around 4 million pounds to purchase.

Mainframes can execute billions of instructions per second and can process
large amounts of data simultaneously.

They are usually connected to a large number of peripherals e.g. printers,
terminals, disk drives etc.

They are used by large companies such as:

      Utility companies e.g. gas and electricity suppliers to calculate customer
      Banks - for managing thousands of customers accounts each day
      Insurance companies - for keeping track of policies and claims
      Airlines - for dealing with bookings, tickets, cancellations etc
      Police - for storing and processing all of the data collected each day about

Mainframe computers need to be operated by specialist, trained staff. They are
usually kept in air-conditioned rooms away from the office or factory floor.

4. Personal Computers
In the early days (1980s) these types of machine were called micro-computers, for
example, schools often had a micro-computer. But now we tend to call them
'desktop personal computers' or just 'PC'.

The desktop PC has a central processing unit housed in a metal or plastic case (often
called a tower unit). A keyboard and mouse are usually used to input data and a monitor
to output the data.

Until recently, most PCs all looked the same, a very boring beige or grey box. Now
manufacturers are coming up with some really interesting designs such as the 'alien'
design on the right.

Modern PCs are quite powerful. They can carry out millions of calculations per second.

They are useful for lots of different types of tasks:

      Running office applications such as word processors, spreadsheets and
      For CAD design such as designing kitchens
      Editing videos
      Creating and playing music
      Accessing the Internet for research, work and entertainment

Laptops were traditionally expensive when compared to a similar specification for a
desktop PC. However, with the growing demand for laptops and cheaper production
methods, they are now a similar price.

The trend towards the use of laptops has been brought about due to many different
Changes in working/living patterns

Many workers are no longer 'chained' to their desk. Many people need to be able to
move about during their working day. This could be going to different offices or buildings
for a meeting or driving to another town for a meeting or conference. It could be that
people want to be able to carry on working whilst travelling to and from work on the

Schools are beginning to provide all staff and students with their own laptops to ensure
that they always have access to a computer no matter where they are in the school.
Think about how many schools there are in the country and how many students there
are in each school - that is an awful lot of laptops needed!
Growth of wireless networking

Over the last few years wireless networking has grown rapidly. This has enabled people
to move around, use their laptops and still be connected to the home or office network
to access files and data.
Improvements in battery life

When the early laptops were developed, the batteries didn't last very long and you
couldn't rely on being able to use your laptop for any length of time.

Batteries now last for long periods of time, making it viable to work for quite a few hours
before the battery needs recharging.
Size and weight

Early laptops were fairly large, bulky and heavy to carry around. This didn't make them
suitable for people who needed to carry them for any length of time.

Laptop design has significantly improved along with smaller, lighter batteries.

Modern laptops are now fairly compact and reasonably light to carry. They can be
stored inside a briefcase, doing away with the need for bulky carrying bags.

6. Personal Digital Assistant (PDA)
A PDA was originally developed as an electronic organiser. They aimed to replace
diaries, 'to do' lists and address books. However, rapid development has resulted in
palm tops and PDAs becoming almost cut down computers in their own right.

PDAs are now available with cut down versions of the main Office software, e.g.
Microsoft Word, Excel and Access. The reason they are so successful is that they
usually have the ability to synchronize with a desktop PC. So, any work you have been
doing on your PDA can be uploaded to your PC and the files updated.

Many PDAs can now also access the Internet and can be used to research web pages,
send emails or even play games. Some even double up as phones.

Palmtops are very similar to PDAs in their use. The main difference is that Palmtops
have a built in keyboard.

7. Embedded Computers
An embedded computer is a single chip that contains all of the elements that are

essential for                                                 any computer i.e.

      RAM
      ROM
      CPU
      Input
      Output
      Clock

Another term often used for an embedded computer is a 'micro controller'. This is
because the main purpose of an embedded computer is to control something.

All of the following contain an embedded computer:

      telephones
      televisions
      cameras
      washing machines
      microwave cookers
      dishwashers
      cars

   1. Introduction(health and safety)

There are various health problems associated with the regular use of computers, such
as stress, eyestrain and injuries to the wrists, neck and back.

Employers must take steps to protect employees whose work involves the regular use
of computers.

This website will introduce you to some of the most common problems and look at what
can be done to reduce the risks.

Work your way through the pages by using the menu on the left-hand side.

   2. Eye Strain
Eyes can become strained after staring at a computer screen for a long time,
particularly if working in bad light, in glare or with a flickering screen.

Fortunately, eyestrain is usually a temporary problem.

Symptoms include:

      Burning or itching eyes
      Blurring or double vision
      Headache
      Nausea
      Fatigue


      Use monitors which don't flicker
      Have blinds at the windows so that the sun doesn't shine directly on the screen
      Use suitable lights that disperse light evenly and don't shine on the screen
      Use a screen filter
      Keep your eyes at least 18 inches from the screen
      Regularly look away from the screen and focus on something in the distance
      Take regularly breaks - at least 5 minutes break every hour
      Have regular eye tests and wear glasses if prescribed

3. Back Pain

Many computer users suffer serious back problems. This is probably due to a poor
posture or an awkward position while sitting at a computer.

Some of the things that people can do to help avoid back pain are:

- Use a fully adjustable chair. The height of the chair and the seat position should be
easy to change.

- Use footrests so that the legs are kept at a more natural angle

- Use a monitor which is adjustable. Position it so that the neck doesn't have to bend

- Take regular breaks and walk about.

- Sit with the back straight and the head up, don't slouch

4. Repetitive Strain Injury (RSI)
Repetitive Strain Injury (RSI) is damage to the fingers, wrists and other parts of the body due to repeated
movements over a long period of time.


In the arms and hands:

       aching
       pain in arms/wrists even after rest
       weakness
       swelling
       tenderness
       numbness
       pins and needles or burning sensation

In the shoulders and neck:

       stiffness
       aching


                                                      Typing or using the mouse for long
        periods of time
       Using too much force on your fingers when typing
       Using a poorly designed keyboard
       Workstation or chair is the wrong height so arms are in an unnatural position


       Ensure workstation and chair are the correct height
       Support wrists by using wrist rests
       Keep elbows close to your sides
       Five minute break from typing at least every hour

5. Stress

Stress brought on through the use of computers is one of the major causes of work
related illness.

There are many different reasons why people become stressed at work. However, here
is a list of some of the major causes brought about by the use of computers:

- Many people are afraid of computers, they don't understand them and feel they will
look stupid if they admit that they don't know how to operate one.

- People worry that a computer will be able to replace them and they might lose their

- Things change so fast in the world of computing that it can be very stressful just trying
to keep up to date with new ideas, techniques and equipment, especially for older

- It is getting increasingly hard to separate work and home life. People can be
contacted easily by their bosses or clients. E-mail, the Internet and mobile phones
mean that people continue to work even after they have left the office.

- The amount of information that ICT systems can produce is often far too much for
anyone to take in. This results in 'information overload' and people end up feeling they
can't cope and become stressed.

- Workers can be monitored using ICT systems. Call centre staff are monitored to make
sure that they don't spend too long on any one call. The number of products that a
check-out person scans during a minute are counted. This feeling of being constantly
'watched' can be very stressful.

6. Safety issues

                                            The workplace can be a dangerous
place. Some precautions which can be taken to reduce the risk of accidents are:

      Ensure there are no trailing wires across or around the room which people could
       trip on
      Electrical sockets should not be overloaded
      Electrical equipment should be safety tested at least once a year
      There should be adequate space around desks for people to move
      Bags and obstacles should be stored out of the way so that people can't trip over
      Food and drink should not be placed near a machine
      Heating and ventilation should be suitable for the working environment
      Work desks should be strong enough to support computers and equipment
      Staff should follow the safety regulations
      Fire extinguishers should be available, including specialist ones to deal with
       electrical fires.
      Fire exits should be clearly marked and free from clutter

7. Employer obligations

                                 Laws have been passed to ensure that employers
provide a safe working environment for anyone who works with computers. This is
called the 'Health and Safety at Work Act (1974).

The law states that an employer must:

      provide tiltable screens
      provide anti-glare screen filters
      provide adjustable chairs
      provide foot supports
      make sure lighting is suitable
      make sure there is sufficient space for people to work
      train employees how to use work stations correctly
      ensure employees have sufficient breaks
      pay for regular eye sight tests for anyone who needs prescription glasses in
       order to use the computer.

NOTE: These regulations only apply to offices and not to students in schools.

8. Ergonomics
This is the science concerned with designing safe and comfortable machines for use by

This includes furniture design and the design of peripherals that you need to use, such
as mouse and keyboard.

Have a look at these top tips to ensure that you work safely and comfortably:

1. The right lighting can reduce eyestrain, neck strain and headaches. Sunlight is the
best light, but make sure it doesn't create glare on your computer screen.

2. The proper desk will let you find the perfect working position. It should be deep
enough to support your arms when you work at the computer.

3. Place your computer screen at eye-level or just below. For optimal comfort, set it
about 45 cm (18 in.) from your face.

4. Sit up straight in your chair. Keep your feet flat on the floor and your knees slightly
lower than your thighs.

5. Choose an office task chair that lets you tilt forward to reach objects in front of you
and backward to stretch your arms when you're tired.

6. When you type, hold your fingers, wrists and lower arms in a straight line from your

7. Keep equipment that you use a lot, like your telephone and computer keyboard,
within a distance of about 75 cm (30 in.) when you're sitting at your desk. Keep other
storage and equipment farther away. This encourages you to change working positions
during the day.

As the name implies, multimedia is the integration of multiple forms of media.
This includes text, graphics, audio, video, etc. For example, a presentation
involving audio and video clips would be considered a "multimedia presentation."
Educational software that involves animations, sound, and text is called
"multimedia software." CDs and DVDs are often considered to be "multimedia
formats" since they can store a lot of data and most forms of multimedia require a
lot of disk space.

Major delivery mechanisms of your multimedia presentation include DVD and CD ROM,
kiosks, computers, the internet, games and displays.

The top uses for multimedia are for presentations, sales and marketing,
education and training, and entertainment.

Here’s how they all come together:

Education and training - A great learning tool, the use of multimedia allows for
interactive learning at the users pace. Learning goals can be identified and met before
allowing the user to proceed to the next lesson. Training sessions can be transportable
on DVD or CD ROM to allow for maximum flexibility.

Sales and Marketing - The use of multimedia at kiosks at trade shows are used to
entertain and educate. They can also be programmed with database functions to gather
information from participants for future marketing efforts. Businesses design flexible
and interactive multimedia presentations to describe their products and services for their
sales force as well.

Presentations - Presentations can be designed so that the presenter can go from one
subject to another, based on a client or audience’s interests or feedback. Sometimes a
little multimedia eye candy can go a long way towards keeping your audience alert and
amused, especially when the content of your presentation is technical.

Displays and Kiosks - Multimedia can also be used in stores to entertain, educate,
engage and market to customers. Whether your customers are standing in line waiting
to check out, at a trade show or walking or driving on the street, multimedia can be used
to engage, motivate and inspire your potential client to make a purchasing decision.

Websites - Want to add pizzazz to your website? Multimedia is the way to go. With
varying levels of interactivity, you can engage your audience and increase the
‘stickiness’ of your site by including interactive tests and quizzes, learning sequences,
and engaging mini-movies.

Entertainment - Multimedia has been used to give life to virtual reality and game
development of all sorts for years. Animation, music, sound, graphics and lots of
multimedia programming are used to give life to these two huge industries.

There are many variations on the themes we’ve just outlined, but these should give you
a brief survey of the major uses for multimedia.

eCommerce (electronic commerce) is the buying and selling of goods and services on the
Internet, especially the World Wide Web. I

Video conferencing uses telecommunications of audio and video to bring people at different
sites together for a meeting. This can be as simple as a conversation between two people in
private offices (point-to-point) or involve several sites (multi-point) with more than one person in
large rooms at different sites. Besides the audio and visual transmission of meeting activities,
videoconferencing can be used to share documents, computer-displayed information, and

The other components required for a videoconferencing system include:

   Video input : video camera or webcam
   Video output: computer monitor , television or projector
   Audio input: microphones, CD/DVD player, cassette player, or any other source of PreAmp audio
   Audio output: usually loudspeakers associated with the display device or telephone
   Data transfer: analog or digital telephone network, LAN or Internet

        Use of ATMs

        Cash Withdrawal and Balance Enquiry

        Cash /Cheque Deposit

        Bill Payments

        Sale of Paper Based Products

What is a computer network?

A Computer Network is a system
of connected computers, peripherals and
communication devices that can exchange
information and share resources.

The network includes the computer systems,
the connections and the hardware needed to
allow the communication.

Networks can be limited to a building/area (a
Local Area Network or LAN) or worldwide such as the Internet (a Wide Area Network
or WAN)

The advantages of networking:

      Computers can communicate with each other easily
      Computers can share data and files.
      Storage facilities can be shared.
      Hardware peripherals such as printers can be shared.
      There is control over which programs, data and hardware a user has access to.
      Data can easily be backed up centrally.

The disadvantages of networking:

      A virus can spread more easily. If a virus gets into one computer, it is likely to
       spread quickly across the network because they are linked.
      As data is shared there is a greater need for security. Users of the network
       have to have user ids andpasswords.
      If the server fails, all the workstations are affected. Work stored on shared
       hard disk drives will not be accessible and it will not be possible to use network
       printers either.
      The cost of installing the equipment is greater. Cabling can be expensive to buy
       and to install.
      Damage to cables can isolate computers. Some sections of the network can
       become isolated and will not be able to communicate with the rest of the network.
      Because networks can be complicated to maintain, a network manager may need
      to be employed to manage the system.

Types of networks:

Networks are divided into two types, a LAN (Local Area Network) or a WAN (Wide Area

LANs - Local Area Networks

Definition - A LAN is a network that is limited to an area such as a building or

In a LAN, computers and hardware such as printers can be connected by cable (copper
wiring), fibre optic cabling (glass fibres) or using a wireless (radio waves) connection.

Advantages of LANs:

      Hardware such as printers can
       be shared so individual
       workstations do not need their own
       printer. When they print, the data
       is stored in a queue on a server.
       The data is then passed to the
      All the users work can be stored
       in a central place (the dedicated
       file server) so a user can access
       their work through any computer
       on the network.
      Software can be shared, software packages are stored on the server and
       downloaded to workstations as requested. Note that a licence still has to be bought
       for each copy of the software needed.
      Data can be shared because database files stored in the server are available to
       users around the network; data from CD-ROMs can also be shared across the
      Central back-up can take place automatically at regular intervals. A user will
       usually be able to retrieve work that has been deleted by mistake.
      Messages can be sent to people working at other computers on the network which
       can save time and paper.
      It is possible to set up a local intranet such as that on the KLB school network. The
       web pages of information can be accessed only over the LAN. An intranet is
       free because it does not involve phone links.
      There is control over users’ access rights to programs and data.

Disadvantages of LANs:

      Printing can be slow. Where a lot of workstations are served by only one or two
       printers, long print queues may develop.
      A virus can spread more easily. If a virus gets into one computer, it is likely to
       spread quickly across the network because it will get into the central backing store.
      As data is shared there is a greater need for security. Users of the network
       have to have authentication techniques such as user ids and passwords.
       Unique user ID's control access to the files and settings on the network
       while passwords prevent unauthorised users from logging onto the network. Data
       may also have to beencrypted so that it is meaningless if intercepted.

      If the server fails, all the workstations are affected. Work stored on shared
       hard disk drives will not be accessible and it will not be possible to use network
       printers either.
      The cost of installing the equipment is greater. Cabling can be expensive to buy
       and to install.
      Damage to cables can isolate computers. Some sections of the network can
       become isolated and will not be able to communicate with the rest of the network.
      Because networks can be complicated to maintain, a network manager may be
       need to be employed to run the system.

WANs - Wide Area Networks

Definition - a Wide Area Network is not confined to one building. The computers
and terminals forming part of the network can be spread around the world.

External communication links such as satellites, microwaves, telecommunication
links and optical fibre will be used to connect the parts of a WAN. The connection must
normally be paid for because the links are external.

The Internet is a worldwide WAN and a LAN can be connected to it using a router.

Advantages of WANs:

      These are similar to those of LAN's except the scale of sharing etc. becomes far
       greater and can be world-wide.

Disadvantages of WANs:

      Again these are similar to those of LAN's except that issues such as security become
       even more important as potential hackers could break into a computer system from
       anywhere in the world rather than having to physically be in a building.
      Encryption of secure data such as financial transactions is necessary because it is
       even easier to intercept data.

Revision points - you should be able to do the following:

      Explain what is meant by a network and know the benefits of networking
      Define a LAN (Local Area Network) and a WAN (Wide Area Network) and discuss
       the advantages anddisadvantages of each

Questions: (Check Answers)

   1. What is a network?
   2. Explain what a Wide Area Network is.

   3.   State one advantage and one disadvantage of a WAN.
   4.   When using a LAN, why is it necessary to have a password?
   5.   Describe the software that makes up a network.
   6.   Describe the devices that make up a typical network.

   1. Answer - A Wide Area Network is not confined to one building. The hardware that
      forms part of the network can be spread around the world.
   2. Answer - Advantages and disadvantages of WANs are the same as for LANs, but
      on a larger scale. WANs can share information around the world. The connection
      must normally be paid for because the links are external. Security is of particular
   3. Answer - A password stops unauthorised users from logging onto the network or
      accessing another users files.
   4. Answer - A network is controlled by network software. This may be part of the
      operating system, or it can be designed specifically to manage the network.
   5. Answer - Cables and connectors are required to link hardware devices together, and
      network cards are built into computers used as terminals in a network. Other typical
      hardware devices that may form part of a standard network are: One or more
      computers acting as dedicated file servers or print servers, scanners and printers.

Define Internet
Internet. A world-wide network of computers linked by telephone lines,
allowing for the global dissemination of information.

The Internet:

       The Internet is the largest WAN. It is a world-wide network of linked computers
        sharing a vast amount of information.
       Advantages:
           o Millions of people contribute information.
           o Data can be rapidly added and updated to reach a huge audience.
           o It can be used to sell goods to a world-wide market.
       Disadvantages:
           o There is a lot of useless information, much of which is out of data and it can
               be very difficult to find what you want.
           o Much of the information is biased, misleading or has not been checked for
           o It is not regulated and offensive and illegal material exists.
           o Issues such as security become even more important as potential hackers
               could possibly be trying to break into a computer system from anywhere in
               the world.

Define www

The World Wide Web, abbreviated as WWW and commonly known as The Web, is a system of
interlinked hypertext documents contained on the Internet. With a web browser, one can view
web pages that may contain text, images, videos, and other multimedia and navigate between
them by using hyperlinks. ...

Define email
e-mail: communicate electronically on the computer;

Advantages of Email
The benefits of e-mail are huge in number.

       Easy to use: E-mail frees us from the tedious task of managing data of daily use. It helps us to
        manage our contacts, send mails quickly, maintain our mail history, store the required
        information, etc.
       Speed: The e-mail is delivered instantly, anywhere across the globe. No other service matches
        the e-mail in terms of speed.
       Easy to prioritize: Since the mails have subject lines, it is easy to prioritize them and ignore
        unwanted mails.
       Reliable and secure: Constant efforts are being taken to improve the security in electronic
        mails. Thus making it one of the secured ways of communication.
       Informal and conversational: The language used in e-mails is generally simple and thus
        makes the communication informal. Sending and receiving e-mails takes less time, so it can be
        used as a tool for interaction.
       Easier for reference: When one needs to reply to a mail, there is a provision in the mailing
        system to attach the previous mails as references. This refreshes the recipient's knowledge, on
        what he is reading.
       Automated e-mails: It is possible to send automated e-mails using special programs like
        the autoresponders. The autoresponders reply back to the sender with generalized pre-written text
       Environment friendly: Postal mails use paper as a medium to send letters. Electronic mail
        thus, saves a lot of trees from being axed. It also saves fuel needed in transportation.
       Use of graphics: Colorful greeting cards and interesting pictures can be sent through e-mails.
        This adds value to the e-mail service.
       Advertising tool: Many individuals and companies are using e-mails to advertise their products,
        services, etc.

Disadvantages of Email
The e-mails, though beneficial in our day-to-day life, has got its own drawbacks that are off late coming to
the fore.

       Viruses: These are computer programs having the potential to harm a computer system. These
        programs copy themselves and further infect the computer. The recipient needs to scan the
        mails, as viruses are transmitted through them and have the potential to harm computer systems.
       Spam: E-mails when used to send unsolicited messages and unwanted advertisements create
        nuisance and is termed as Spam. Checking and deleting these unwanted mails can
        unnecessarily consume a lot of time, and it has become necessary to block or filter the unwanted
        e-mails by means of spam filters. Spamming includes, sending hoax e-mails. E-mail spoofing is
        another common practice, used for spamming. Spoofing involves deceiving the recipient by
        altering the e-mail headers or the addresses from which the mail is sent.

      Hacking: The act of breaking into computer security is termed as hacking. After the e-mail is
       sent and before it is received by the desired recipient, it "bounces" between servers located in
       different parts of the world. Hence, the e-mail can be hacked by a professional hacker.
      Misinterpretation: One has to be careful while posting any kind of content through an e-mail. If
       typed in a hurry, the matter could be misinterpreted.
      Lengthy mails: If the mail is too long and not properly presented the reader may lose interest in
       reading it.
      Not suitable for business: Since the content posted via e-mails is considered informal, there
       is a chance of business documents going unnoticed. Thus, urgent transactions and especially
       those requiring signatures are not managed through e-mails.
      Crowded inbox: Over a period of time, the e-mail inbox may get crowded with mails. It
       becomes difficult for the user to manage such a huge chunk of mails.
      Need to check the inbox regularly: In order to be updated, one has to check his e-mail
       account regularly.

       Define search engine

       A place, on the Net, where one goes to find sites about specific
       information. When you have a Web site and you want people to be able to
       find it you must go to the search engines and submit your site to them .

Define Computer virus

A computer virus is a program which copies itself.

Often a virus attaches itself to other programs which are
then saved with the virus added to them. Most viruses do
not affect data files.

Some viruses attach themselves to emails and propagate
by sending themselves to all the email addresses stored on
the computer.(In the address book)

The virus usually does more than just copy itself. It may
erase files or corrupt the data on the screen.                      Examples :

                                                                    (a) The Michelangelo Virus. This infects
Protection : Viruses can cost commercial firms a lot of
                                                                    files on March 6th, which was
money. Steps they can take to protect themselves are :              Michelangelo's birthday. On that day, if it is
                                                                    not stopped, it deletes the files on the hard
      use a commercial program which
       can detect andremove viruses.
                                                                    (b) The Cascade Virus. This also has
      avoid the use of programs of doubtful origin eg              particular dates when it becomes active,
       shareware.                                                   causing all characters on the screen to fall
                                                                    in a jumbled mass to the bottom of the
      backup files regularly.
      do not open attached files on emails if you do not

know the sender.


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