Spn year 7 notes

Pages

1. Introduction to computers 1

2. Computer Lab Personal safety rules 4

3. Basic principles of computers 6

4. Parts of computer 8

5. Computer System Electrical Connections 14

6. Care for computer systems, storage media and simple health issues
15

7. Input Devices (Manual) 18

8. Input Devices (Automatic) 25

9. Output Devices 30

10. Storage devices 36

11. Troubleshooting Computers 43

12. Bits and Bytes 45

13. Types of computers 47

14. Types of Software 52

15. E-mail 57

16. Basic of Windows 61

17. Internet 65

18. Graphics 72

19. Word Processing 78

Computer Studies SPN 21 Form 1

1. Introduction to computers
1. What is a computer ?

A computer is a piece of equipment that can be programmed (instructed) to perform certain
functions. It processes data quickly and accurately.

• What does a computer look like?

Typical desktop computer Early days computer

Personal Computer A COMPUTER is basically a processor of information.

2. Characteristics of a computer :

A computer is able to:

• process
• store
• input
• output

data or information

The characteristics of a computer :
• It is an automatic machine.
• It processes data quickly and accurately.
• It has no feelings or emotions like human beings.
• It can recall any stored information when needed.
• It cannot think on its own, but follows instructions.
• It has a storage capacity for storing data and instruction.

Prepared By : Juliet Hoh Page 1


3. Special-purpose and General-purpose computers

Special-purpose computers

– designed to do a specific job
– usually expensive
– E.g. ATM, computers in aircrafts, MRT trains, traffic light system….

General-purpose computers

– designed to do many kinds of jobs.

*Entertainment * Word processing * Surfing the Web etc.

- Usually cheaper

- E.g. Personal computers, notebooks..

4. The tasks of a general-purpose computer

Performs calculations
Send e-mail messages
Write documents
Draw graphics
Surf the net

5. What is a program ?

A program is a set of instructions for the processor to complete a job.

• It is created by programmers.
• All programs are software.

6. Types of software



Operating systems

The Operating system is needed to control everything happening in your computer. It controls
the memory, the disks, the peripherals and the application software.

E.g. of OS : Windows, Dos

Application software

Application software are programs such as browsers that carry out a specific task or set of
tasks.

Other examples include : - word processors, spreadsheets, accounting packages, games



2. Computer Lab Personal safety rules
Take good care of your computer and it will serve you longer. In school, students must be
responsible when using the computer system.

1. Report any faulty computer and peripheral to your teacher immediately.

2. Do not bring food and drinks into the computer laboratory. Food spillage onto the
computer will damage the equipment.

3. Do not push or knock computers especially when they are running

4. Keep your computer clean. If your computer is dirty or dusty, wipe with a dry cloth
before turning it on. Do not use harsh chemical. Wash and dry your hands before
handling a computer.

5. Follow proper steps in switching on and off your computer.
Switching on peripherals first then the computer
Switching off computer first, then the peripherals

6. Care of the computer mouse
Do not remove the ball.
Do not pull mouse away from the computer.
Do place mouse on a mouse pad.



7. Inform your teacher when the printer is
Not working
Jammed
Out of ink

To avoid false alarm, first make sure that the printer is not
Switched off
Out of paper
Disconnected from the computer

8. Do not remove a disk when the disk drive indicator is blinking.

9. Do not place strong magnets near the computer system
hard disk can be damaged
data will be lost

OR

1. Obtain teacher's permission before performing any activity in the laboratory.
2. Report fire or accidents to your teacher immediately.
3. Report to your teacher if you notice any broken plug or cables.
4. Sit in front of your computer in the right posture.
5. Avoid stepping on any wires or cables.
6. Do not run in the laboratory.
7. Do not play in the laboratory.
8. Do not eat in the laboratory.
9. Do not drink in the laboratory.
10. Do not open the system unit casing or monitor casing especially when the power is ON.
11. Do not insert any metal objects into the computer casings. It may cause fire.
12. Do not touch, connect or disconnect any cable without teacher's permission.



3. Basic principles of computers
1. The basic operations of a computer

A computer cannot work on its own without programs. A program consists of step-by-step
instructions telling the computer what and how to do it. Without instructions, computers
cannot do anything.

People need instructions to do something too.

• Do people and computers carry out a task in similar ways?
• Compare how people and computers divide 2,760 by 4

2. Input & Output

What comes out of a computer system is largely dependent on what you put in the system.

GIGO can be interpreted in 2 ways :

1. Good Input, Good Output

Computer systems work by taking inputs (instructions and data), processing them and
producing outputs that are stored or communicated in some way. The higher the quality and
better thought-out the input, the more useful will be the outputs.

2. Garbage In, Garbage Out

ICT systems cannot function properly if the inputs are inaccurate or faulty; they will either not
be able to process the data at all, or will output data which is erroneous or useless.



3. A simple block diagram Both people and computers do the following:

Input Process Output

↓ ↑
Storage


Storage

Take in data / info Work on data / Produce the result



4. Parts of computer

1. Introduction
Computer Systems are made up of many different parts, for example hardware, software,
processors, memory etc.

It is important that you have a basic understanding of some of the main parts of a computer.



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

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

3. Software
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

HARDWARE SOFTWARE
Definition computer equipment computer program
Example monitor, keyboard, Microsoft Word, Microsoft
mouse Excel
Cost Cheap Expensive
See Yes Yes, once it is printed
Touch Yes No (Cannot touch)

4. Peripherals
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



5. 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.

6. CPU Components
You need to have a basic understanding of the three main parts of a CPU.

These are the: 1) Control Unit

2) Immediate Access Store

3) Arithmetic and Logic Unit

The Control Unit

This has three main jobs:

1. It controls and monitors the hardware attached to the system to make sure that the
commands given to it by the application software are used. For example, if you send
something to print, the control unit will keep a check that the instructions are sent to
the printer correctly.
2. It controls the input and output of data so that the signals go to the right place at the
right time
3. It controls the flow of data within the CPU

The Immediate Access Store

This holds the data and programs needed at that instant by the Control Unit.

The CPU reads data and programs kept on the backing storage and stores them temporarily
in the IAS's memory. The CPU needs to do this because Backing Storage (e.g. the hard disk)
is much to slow to be able to run the applications from it directly.

For example, lets pretend that a modern CPU was slowed down to carry out one instruction
per second. In this scenario, the hard disk slowed down to an equivalent rate would take
three months to supply the data needed by the CPU!


Arithmetic and Logic Unit

This is where the computer processes data either by manipulating it or acting upon it. It
consists of two parts:

1. Arithmetic part - which does exactly what you think it should - it performs the
calculations on the data e.g. 3 + 2 = 5
2. Logic part - this deals with logic and comparisons. For example, it works out if one
value is greater, less than or equal to another.

7. Motherboard
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 peripherals.

8. 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.



9. Memory
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)

In contrast to ROM, 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.

2 Main Memory are :

RAM ROM
Random Access Memory
Read Only Memory
stores information temporarily
stores information permanently
Data can be changed
Information inside cannot be changed
Data is lost when PC switched off.
Data is safe when PC switched off.



10. Cache Memory

Most data is stored on the hard disk. When we use that data, it is loaded into RAM because it
is much faster to access the data from RAM than from the hard disk. When we looked at the
'immediate access store' earlier, we found out that the CPU needs to access data very
quickly. Although RAM is faster than the hard disk, it still isn't fast enough to cope with the
speed that the CPU needs to deal with data.

The cache is a special type of computer memory which can be accessed much faster than
RAM. The CPU looks in the cache for the data it needs. If the data is there, it will retrieve it
and process it. If the data is not there, then the CPU accesses the system memory and then
puts a copy of the new data in the cache before processing it.

Cache memory is volatile i.e. when the computer is shut down, the data stored there is lost.



5. Computer System Electrical Connections
•
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• A computer is made up of different parts
• Each part performs different function or operation

The casing of the system unit

• Casing is aluminium coated
• Extremely durable
• Commonly called Central Processing Unit (“CPU”)
• Contains a processor

Wired and wireless computer parts Computer parts classified into wired and wireless ones :

1. Wired computer parts

• Physically connected by wires or cables
• Connected to attachments called ports

2. Wireless computer parts

• No physical connection
• Example: wireless router, cordless mouse



6. Care for computer systems, storage
media and simple health issues
4.1 Things that Storage Media are Made of

• To understand how storage media is to be taken care of, we must first understand
what they are made of

Diskettes

• Data is stored in a thin plastic disk
• Can be easily bent
• Can be easily scratched
• Cannot withstand heat

Recordable Compact Disc (CD-R)

• Stores up to 700 MB of data
• Data is stored on a thin foil stuck to the surface of the CD
• CD-R cannot withstand scratches

Hard disk

• Store information on a platter
• Platter spins at head speed
• Vibration or shock can cause surface of the disk to be scratched
• Important not to drop a hard disk

Thumb drive

• Store information in memory chips
• Vulnerable to static electricity and humidity
• Keep away from static electricity and humid places (e.g. pockets)
• Care of storage media
• Take care of storage media to prevent data loss

Diskettes

• Diskettes are sensitive equipment
• Handle correctly so that they will last as long as intended
• Most diskettes have warning against improper handling
• Keep the following away from your diskettes …

Your fingers

• Do not touch the media inside. This may damage the media.



Magnets

• Data is stored in the diskette’s magnetic media. Magnets can corrupt the
data.

Dusty places

• Dust can cause scratches on the surface of a diskette.
• Liquids (e.g. coffee, water)
• Liquids will leave behind a thin film of dirt on the surface of a diskette.
They may react with the magnetic material, thereby damaging the
diskette.
•
• Heat
• When exposed to heat, the piece of plastic media can warp (lose its
shape). Most diskettes are safe if stored at between 10–60°C.

• CD-ROM
• How do we take care of CD-ROM?

1. Always hold a CD by its edge or centre hole

2. Do not

• scratch
• Write
• Paste a sticker
• on a CD

3. Do not

• Put the CD
• In a very hot place
• Under the sun (The plastic may melt)
• Leave it in the open

4. Do not put heavy items on the CD

5. Do

• Keep it in the shade
• Enclose it
• Keep CD clean
• Wipe gently with soft cotton cloth



(a) Floppy Disks

DO DON'T
Use the envelope provided to cover your disk. Do not touch the inside black plastic disk.
Use the soft tip pen to write on the diskette
Do not bend or fold the diskette.
surface.
Keep disks out of direct sun heat which will Do not apply any force/pressure on the
bundle the diskettes. diskette surface.
Keep disks away from magnets/static
electronically.

(b) CD-ROMs

'CD-ROM' stands for Compact Disk Read Only Memory.
Information stored in a CD-ROM cannot be changed.
They are made of special plastics with a metallic coating.
The storage capacity is as high as 650MB.
They are commonly used to store text, audio and video information.
They can last for more than 100 years.
They are usually 10 to 15 times slower than hard disk drives.
CD-Recordable drives allow you to store your own information on CDs. The Writeable
CDs are generally used to backup hard disks or distribute information.

DON'Ts
DO's

When handling a CD-ROM, hold the disk Do not write on a CD-ROM with a
around the edge. pen/pencil/marker pen.
Place the CD-ROM in its casing after use. Do not expose CD-ROMs to dust or dirt.
Do not expose CD-ROMs to direct
Store CD-ROMs at normal temperature.
sunlight.
Insert a CD-ROM gently into the CD-ROM
Do not peel off the label on a CD-ROM.
drive by holding the edge.



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

2. Keyboard
The keyboard is the most common and widely used input device.

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 right)
• 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.

Advantages

• 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

Disadvantages

• 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.



3. Mouse
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.

A mouse usually has two buttons, a right and left one and also a central wheel which allows
you to scroll up and down the page (some mice have three or four buttons). The left and right
button have different functions. Left clicking usually lets you put your cursor at a certain point
on the page or lets you choose a menu item. Right clicking brings you up a list of relevant
menu items from which you can select a task.

Many of the older styles of mice used a ball which moved against two internal rollers to
record the direction that the mouse was being moved in. Recent versions of mice use 'optical'
or 'wireless' technology to track mouse movement.

Advantages

• 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

Disadvantages

• 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

4. Touchpad
A touchpad is an input device which is usually found on a laptop computer.

Because a laptop is meant to be portable, people aren't always able to attach a traditional
mouse, it might be too much hassle or there might not be enough room to use one. A
touchpad can be used in place of a mouse.

By dragging your finger over the surface of the touchpad, sensors underneath detect the
movement direction and speed. The sensors only react to a fingertip and not a pencil or other
object. There are usually two buttons next to the touchpad which are used to replace the left
and right mouse button.



Advantages

• Useful for laptops when using a mouse isn't practical
• The pad's position is fixed compared to the keyboard, unlike with a traditional mouse
• Very short finger movements are required to move the cursor

Disadvantages

• Takes practice and skill to control the position of the cursor using the touchpad
• Gloves cannot be worn i.e. in a clean room environment
• Moist, sweaty or calloused fingers can disrupt the signals picked up by the sensors.

5. Joystick
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.

Advantages

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

Disadvantage

• 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
them.

6. Concept Keyboard
A concept keyboard is a flat board that contains a grid of buttons. Each button can be
programmed to do whatever you want. An overlay sheet with pictures or symbols is placed on
the grid so that the user can tell what pressing on different areas will do.

Concept keyboards are used when fast input is needed and are ideally suited to selecting
from a limited range of choices such as fast food restaurants. Checkout tills such as
McDonalds use symbols to make ordering faster and easier. Primary schools often use them
with young children. The overlay image could be a picture of a farmyard. Pressing on an
animal would cause the computer to make the right animal noise.



Concept keyboards are particularly useful for people who would find using an ordinary
keyboard difficult. It is also very handy in locations where an ordinary keyboard might be
damaged e.g. by spillage or dust.

Advantages

• Much faster for making non-text selections such as menu choices on the till of a fast-
food outlet.
• The keyboard is waterproof which can be useful where there is dirt or the risk of
splashes

Disadvantages

• Poor for text or numeric input - although some keyboards do include a numeric keypad
so the operator can enter the amount sold.
• Limited to the options shown on the keyboard.

7. Touch Screen
A touch screen is the only device which works as both an input and an output device. You
view the options available to you on the screen (output) and you then use your finger to touch
the option that you have chosen (input).

Touch screens work particularly well with a menu driven interface. For example, a cashpoint
(ATM) at a bank would first of all ask which service you want. You touch the option 'withdraw
cash' on the screen. You are then presented with another choice, 'how much cash do you
want to withdraw?'. Once you have chosen how much, you then get other options such as 'do
you want a receipt?'.

Touch screens are easy to use and are often found in public places such as cashpoints at
banks, ticket collection terminals at theatres or airports, information centres at museums.
Touch screens are not commonly used to input large amounts of data because they are not
very accurate and they would be tiring on the hands to use for long periods of time.

Advantages

• Easy to use - intuitive, don't need much training
• No extra peripherals such as a mouse are needed
• Software can alter the screen while it is being used, making it more flexible than a
concept keyboard which has a permanent overlay.

Disadvantages

• Not suitable for inputting large amounts of data
• Not very accurate - selecting detailed objects can be difficult with fingers
• Tiring to use for long periods
• More expensive than alternatives such as a mouse
• Not robust - can soon become faulty if misused.


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

A scanner works by shining a beam of light onto the surface of the object that you are
scanning. This light is then reflected back onto a sensor that detects the colour of the light.
This is then used to build up the digital image.

Items that are scanned are usually stored in an image format. However, special software -
Optical Character Recognition - can be used to convert text on the paper into text which can
be edited with a word processor. However, the text doesn't always get converted very well
and you could end up with a lot of mistakes.

There are two types of scanner:

1) Flatbed scanners

2) 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.

Advantages

• 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
documents
• Images once digitised can be enhanced with a graphics application

Disadvantages

• 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



9. Digital Camera
A digital camera records images electronically on a memory card rather than on film as did
the older models of camera. The images can be downloaded from the memory card onto a
computer and then printed, stored or manipulated with a photo editing application.

Most digital cameras let you view the image as soon as you have taken the picture; if you
don't like what you see, it can be deleted. The quality of the image is dependent on the
resolution or the number of pixels. Most digital cameras range from 4 - 12 Megapixels
(millions of pixels in the image).

The more pixels, the better the quality and clarity of the image.

Many digital cameras are now capable of taking short video clips along with sound.

Advantages

• No film is needed, no developing costs to view the pictures
• Images can be viewed immediately and unwanted images can be deleted
• Images can be edited, enlarged or enhanced
• Images can be incorporated into documents or added to web sites
• Extra memory sticks can be purchased to store images

Disadvantages

• Digital cameras are generally more expensive than ordinary cameras which use film
• Images often have to be compressed to avoid using too much memory
• When the memory is full, the images must be downloaded to a computer or deleted
before any more can be taken.

10. Graphics Tablet
Graphics tablets are often use by graphics designers and illustrators.

Using a graphics tablet, a designer can produce much more accurate drawings on the screen
than they could with a mouse or other pointing device. Drawings created using a graphics
tablet can be accurate to within hundredths of an inch. A graphics tablet consists of a flat pad
(the tablet) on which you draw with a special pen. As you draw on the pad, the image is
created on the screen.

Advantages

• It is much more natural to draw diagrams with a pencil type implement (the stylus)
rather than with a mouse
• A great level of accuracy can be achieved


Disadvantages

• Not really suitable for general selection work such as pointing and clicking on menu
items
• Graphics tablets are much more expensive than a mouse

11. Microphone
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.



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

2. Magnetic Ink Character Recognition

Each day, banks process millions of cheques. It would take them far too long to manually
enter the data from each cheque. They use a technique called 'Magnetic Ink Character
Recognition' (MICR) which enables them to process 300 cheques per minute with 100%
accuracy.

At the bottom of each cheque are a series of numbers which record:

• the cheque number
• the bank or building society sort code
• the customer's account number

These numbers are written in a special ink which contains iron particles. This ink is
magnetised and commonly called 'magnetic ink'. It can be read by a special machine called a
Magnetic Ink Character reader (MICR).

The MICR will only recognise numbers printed in a standard font using the magnetic ink. This
provides a high level of security because any attempt to alter the magnetic ink printout with
normal ink by writing over it will be ignored.

Both the Reader and the magnetic ink are expensive and so are generally only used by
banks.



3. Optical Mark Reader (OMR)

Have you ever looked closely at the National Lottery ticket selection form? Or have you ever
had to do a multiple choice test at school where you had to use a pencil to show your answer
(like our picture on the right)?

These forms are scanned by a special piece of equipment called an 'Optical Mark Reader'
(OMR). they detect the presence of your pencil mark by reflecting light onto it. Less light is
reflected where a mark has been made.

The OMR then interprets the pattern of marks and sends the results to the computer for
storage, analysis and reporting.

Advantages

• A fast method of inputting large amounts of data - up to 10,000 forms can be read per
hour depending on the quality of the machine used.
• Only one computer needed to collect and process the data
• OMR is much more accurate than data being keyed in by a person

Disadvantages

• If the marks don't fill the space completely, or aren't in a dark enough pencil, they may
not be read correctly
• Only suitable for recording one out of a selection of answers, not suitable for text input
• The OMR reader needs the answers to be on the prepared forms which will all be
identical to one another. You can't just pick up a blank sheet of paper and mark your
answers on it.



4. Optical Character Recognition (OCR)
An OCR system consists of a normal scanner and some special software. The scanner is
used to scan text on a document or piece of paper into the computer. The OCR software then
examines the page and changes the letters into a form that can be edited or processed by a
normal word processing package.

The ability to scan the characters accurately depends on how clear the writing is.

Scanners have been improved to be able to read different styles and sizes of text as well as
neat handwriting.

Although they are often up to 95% accurate, any text scanned with OCR needs careful
checking because some letters can be misread.

OCR is used to automatically recognise postcodes on letters at sorting offices.

Advantages

• Cheaper than paying someone to manually enter large amounts of text
• Much faster than someone manually entering large amounts of text
• The latest software can recreate tables and the original layout

Disadvantages

• Not 100% accurate, there are likely to be some mistakes made during the process
• All documents need to be checked over carefully and then manually corrected
• If the original document is of poor quality or the handwriting difficult to read, more
mistakes will occur
• Not worth doing for small amounts of text



5. Barcode Reader
Most items that are for sale in shops have a barcode printed somewhere on the packaging.

The barcode is a series of vertical bars of varying widths that give information about:

• the country of manufacture
• the name of the manufacturer
• a product code

The barcode does NOT contain the price of the item - this is held on the company database.

A barcode reader is an automatic input device which is used to scan or 'read' the barcode by
using a visible red light. The reflected light is translated into digital data that is interpreted by
the computer to identify the product and price from the database.

The main advantage of using a barcode system is that any price change only needs to be
made to the database and not every single product package.

Barcodes are also used on books to show the book's ISBN number - have a look at any
textbook that you have in your bag. They are also used on library tickets so that when your
ticket is scanned, the database brings up your account and any books which you still have
out on loan are displayed.

6. Magnetic Stripe Reader
Magnetic strips are usually found of the back of most credit cards, cheque guarantee cards,
loyalty cards, membership cards etc.

The magnetic strip can hold personal details about the card number such as account number,
name and Personal Identification Number (PIN). The strip can contain up to 60 characters,
stored magnetically.

To read the data on the card, it is 'swiped' through a Magnetic Stripe Reader machine and
the data is read and fed back to the computer.

Advantages

• Simple to use, Cheap to produce, Data can be altered if necessary
• Security has been improved by the use of PIN numbers which must be entered into a
machine to confirm that you are the rightful card owner

Disadvantages

• Very limited storage capacity for data
• Data can be easily destroyed by strong magnetic fields
• Not always secure as thieves can obtain the readers and read the data on the card.


7. Biometric Devices

There is an increasing trend towards using biometric data from people in order to identify
them. Finger print and retinal identification are being used in many places now and even
facial recognition systems are starting to be introduced.

Special devices are needed to capture the biometric data which is then passed onto the
computer for processing and identification.

Biometric authentification methods can be used to identify you at ATMs to withdraw cash, in
computer networks to allow you to log on and many schools are now introducing 'fingerprint
registration'!

8. Sensors
Sensors are used to detect physical quantities outside a computer such as light, temperature
and pressure.

They collect data automatically and usually at regular intervals. This data is can either be
transmitted immediately to the computer or can be stored for a period of time and a batch of
readings sent in one go.

In order to process input from sensors, a device called an 'Analogue to Digital Converter'
(ADC) must be connected between the computer and the sensor. This device converts the
analogue signals from the sensors to digital data that the computer can process.

Finger print and retinal identification are being used in many places now and even facial
recognition systems are starting to be introduced.

Special devices are needed to capture the biometric data which is then passed onto the
computer for processing and identification.

Biometric authentification methods can be used to identify you at ATMs to withdraw cash, in
computer networks to allow you to log on and many schools are now introducing 'fingerprint
registration'!



9. Output Devices
1. Introduction

This section will introduce you to the most common output devices, ranging from computer
monitors to lights.

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

They come in many different shapes, sizes and forms. 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 output.

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:

• Print created by pushing heated pins against heat sensitive paper
• Cheap and fast
• Used widely in supermarket checkouts and ATM

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.

Advantages

• 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

Disadvantages

• 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 time.

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.

Advantages

• 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

Disadvantages

• 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

6. 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.

Advantages

• 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
factories.


Disadvantages

• Print quality is poor and important documents are not suitable to give to managers or
customers
• 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

Printer Type Dot Matrix Printer Ink Jet Printer Laser Printer
Cheaper depends on
1. Cost Cheap Expensive
quality and speed
2. Size Bulky Lighter Heavy
3. Resolution Low/draft quality Near letter quality Letter quality
4. Speed 100-400cps (Slow) 2-10ppm (Faster) 4-17ppm (Fastest)

5. Noise
Noisy Quiet Silence
Level
6. Used Ribbon Ink Cartridge Toner
Very popular because of
Less demand on it Slightly popular apart
7. Popularity the colourful hardcopies
nowadays from its expensive price
that it can print
It has a print head A print head with a no. of
Images are transferred
with a number of tiny nozzles. It uses
onto a piece of paper with
8. Mechanism pins. These pins melted wax in cartridge
'ink powder' using a laser
move and form dots packing to form tiny dots.
beam.
on paper.



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:

1. Flatbed plotters

- These hold the paper still while the pens move

2. Drum plotters

- These roll the paper over a cylinder

3. Pinch-roller plotters

- These are a mixture of the two types above

Advantages

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

Disadvantages

• 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



8. Speakers
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.

Advantages

• 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

Disadvantages

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

9. Lights
Lights such as LEDs (Light Emitting Diodes) can be connected to a computer and respond to
electrical signals which tell them to switch on and off.

Control devices such as lights, buzzers and motors are used when the computer is controlling
a situation such as traffic lights.

Advantages

• They can be used in a computer control simulation and help provide evidence that the
simulation is working correctly
• They can provide a warning for users with hearing loss who might not be able to hear
the error beeps produced by the internal speaker.
• They come in a large range of different colours

Disadvantages

• The bulb may break or wear out and need replacing
• There may be a loose connection which means the light doesn't switch on even if the
circuit or control program is correct



10. Storage devices
1. Introduction
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 tasks.



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 reboot 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 512Mb - 1Gb 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.

In order to access the data, the platters spin many thousands of times a second and a
magnetic read and write head floats just above the surface of the platter.

When you hear the term 'hard disk crash', this refers to the read/write head crashing down
onto the surface of the hard disk. There is a risk every time this happens that the data stored
in the section just where the head crashes might be damaged. That is why it is a bad idea
just to switch the computer off at the wall without shutting it down properly.

Hard disks are measured in Gigabytes. A typical hard disk size will be around 120 Gb - 1
Terabyte.

It is possible to also have an external hard disk which can be plugged into the computer and
used to back up your data and then stored in a different place to keep it safe.


Advantages

• 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

Disadvantages

• 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
sector
• The disk is fixed inside the computer and cannot easily be transferred to another
computer.

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 nowadays, 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.

Advantages

• 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

Disadvantages

• 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



7. Zip Disks
Zip disks are pretty much obselete now. However, they were very popular as a backup
medium before CD-RWs were developed and became cheap enough for everyone to use.

Zip disks look similar to a floppy disk but are a little bit thicker. Computers generally didn't
come with a zip drive installed, so you couldn't just use one in the same way as a floppy disk.
You needed a separate plug in drive, which was an extra expense. They can store around
100Mb of data - 70 times more than a floppy disk.

Advantages

• Stores more data than a floppy disk
• Compresses data, reducing the file size, so more data can be stored
• Portable

Disadvantages

• Almost obselete now
• Need a seperate zip drive to read the disk
• More expensive than floppy disks

8. Magnetic Tape
The amount of work that you do on your computer at home can easily be backed up onto a
CD-RW or a memory stick. However, many organisations, such as your school or an office,
need to back up large volumes of data each day. A CD-RW, DVD-RW or flash memory sticks
just would not be large enough for doing this.

Large organisations who need to back up their systems daily tend to use magnetic tapes to
store their data. Magnetic tape uses 'serial access' to find a piece of data. It works in much
the same way as a video tape that you might have at home. To find a specific piece of data,
you have to start at the beginning of the tape and continue fast forwarding until you get to the
piece of data that you need. This makes it fairly slow to find and retrieve data so it would not
be much use to store data that you needed to get hold of quickly.

Advantages

• relatively cheap per megabyte of storage
• can store large amounts of data - over 100 Gb
• can be set up to do the back up overnight or over the weekend

Disadvantages

• serial access so can be quite slow to access data
• need a special piece of equipment to record and read the data on the tape



9. 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 650 Mb of data - equivalent to 450 floppy disks. The
entire contents of four text based encyclopedias (no images) could be stored on a single CD.

Advantages

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

Disadvantages

• 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 home.

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.



One problem with the DVD is that the different companies which make them haven't agreed
on a standard format. Because of this, you will see various kinds of DVD disks for sale: DVD-
R, DVD+R, DVD-RW and DVD+RW. You have to make sure that you buy the right kind of
disk to go with your DVD equipment.

Advantages

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

Disadvantages

• 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 8 Gb.

Advantages

• 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.

Disadvantages

• 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



11. Troubleshooting Computers
1.2 Troubleshooting Computers

• getting a computer to run again after they failed to do so
• When a computer does not start
• Check cable connections
• Check power cable
• Check monitor cables
• Common error messages
• 1) Error messages tell you what the problem is
• Error message when computer is booting up:
• Non-system disk or disk error
• Replace and strike any key when ready
• Solution:
• Remove any floppy disk, CD-ROM and reboot
• May be hard disk problem
•
• 2) Error message while working
• Not enough memory
• Insufficient memory
• Solution:
• Too many programs running, close some
• Clear unwanted/ obsolete files
• Memory leaks, restart computer

• Other problems
• Monitor screen blank
• Solutions
• Monitor turned on?
• Monitor in sleep mode?
• Check power code is connected
• Check brightness level of monitor
• Computer not giving out sound
• Solutions
• Speakers turned on?
• Volume turned up?
• Mute button checked?
• Speakers turned on?
• Volume turned up?
• Mute button checked?
• Computer freezes or “hangs”
• Solution
• Shut down programs that are not responding using Windows Task
Manager
• If all else fail, turn off power and restart computer



Summary

• All computers need software to work. An operating system (OS) is a form of software
to operate the computer.

• An OS comes with a set of very basic programs (e.g. Write). If these basic functions
do not have the functions that you want, you will need to install more elaborate programs.

• In running a program, the OS allocates the computer’s memory and passes partial
control of the CPU to it. The OS will not check what the program is doing.

• A program is a series of instructions. In a commercial program, there are millions of
lines of instructions.

• The work in getting computers to run again after a failure is called troubleshooting.

• When your computer does not start, check all the cables and connections. Push in the
cables gently.

• Error messages are ways by which the computer tells you what the problem is. E.g. if
the error message “Not Enough Memory” appears, try closing some applications.

• If your computer “hangs”, press Ctrl + Alt + Del which will display the Task Manager
dialog box and end the applications that are not responding. If this does not work, restart
your computer by turning the power off and then on.



12. Bits and Bytes
A binary number is either a 0 or a 1 and is known as a 'bit' or binary digit .

However, the CPU cannot deal with just one bit at a time, it is just too small. It usually deals
with 8 bits at a time, which is known as a Byte . ( K is short for kilo ,1Kb is one kilobyte, M is
short for mega, 1 Mb is one megabyte)

11100101 is a byte, 10000111 is also a byte, or any other combination you can think of which
contains 8 zeros and ones.

Why does all this matter?

We often need to process words, so the computer must be able to store letters and other
keyboard characters. This is done by making up a code. Each number represents a charact.

One common code is A=65, B = 66 and so on. This is called ASCII code or American
Standard Code for Information Interchange.

Each ASCII character occupies just one byte. The eight bit binary code or byte which
represents the letter A is

0 1 0 0 0 0 0 1

The word JOHN would take 4 bytes of memory to store.

RAM can store millions of bytes. So of course all that information needs to be accessed by
the CPU. It does this through a method called, 'addressing'. Every location in RAM has a
unique address.

Each storage location (address) contains a byte which represents data in the form of:

- a number

- a character or string of characters

- a computer instruction

- part of a picture

- the address of a location in store



But remember - all this information is stored as strings of 1s and 0s i.e. binary code

Quantity Information

This is the lowest 'data' level and is a series of 0s and 1s,
8 bits = 1 byte.
e.g. 00111010 = 1 byte with each 0 or 1 equal to 1 bit.

Each keyboard character = 1 Each number, letter and keyboard symbol is represented
byte. by a series of 8 bits (each, of course, is different).

1000 keyboard characters = 1000 In reality it is really 1. 024 bytes which make a kilobyte, but
bytes or 1 KB (kilobyte). generally people refer to 1000 bytes as a kilobyte.

1000 kilobytes = 1 MB (1 million Floppy disks have a capacity of 1.44 MB . CD ROM disks
keyboard characters). have a capacity of 650 MB.

1000 megabytes = 1 GB
DVD disks can hold between up to 4.7 GB of data.
(gigabytes or 1 billion characters)



13. Types of computers

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

Microcomputer Minicomputer Mainframe Computer

1.Introduction Referred to PC Mini for short Mainframe for short
Small-sized
2. Size Medium-sized computer Large-sized computer
computer
3. Cost Cheap Expensive Very Expensive
4. Use Easy to use Difficult to use Difficult to use
Single-user Multi-user Multi-user
5. User
(1) (10 - 60) (More than 100)
Medium-sized business
Big business and
6. Used For Personal use or organizations, banks
government departments
and etc
Low computing Very High computing
7. Power High computing power
power power
Normal or air- Special air-conditioned
8. Room Air-conditioned room
conditioned room room
9. Example PC Clones IBM 36, HP 9000 CRAY-2, VAX 9000
Word Processing,
Spreadsheet, E-
mail, Games
Airline reservation, weather
(Home Control ATM at the banks,
forecasting, Space vehicle
10. entertainment), Inventory control for
control, big universities, to
Applications Graphic (designing supermarket, Hospital
detect oil and gas field in
clothes/shoes) registration and ...
the sea (BSP) and …
and ...



2. Supercomputers
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 research.

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 bills.

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 crimes

Mainframe computers need to be operated by specialist, trained staff.

They are usually kept in an 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 BBC 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 databases

- For CAD design such as designing kitchens

- Editing videos

- Creating and playing music

- Accessing the Internet for research, work and entertainment

5. Laptops
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 reasons:

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 train.

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
• TVs
• Cameras
• Washing machines
• Microwave cookers
• Dishwashers
• Cars



14. Types of Software
1. Introduction
Software refers to the programs that we run on our computer systems.

Software allows the hardware to do something useful; without software, the hardware
wouldn’t know what it was supposed to do.

Software is made up of a series of instructions or computer code. It is these instructions
which tell the hardware that it needs to print a document or save a file or display a webpage.

2. Software Categories
There are two main categories of computer software that you

need to know about. They are:

1. System software – the Operating System, utility programs and drivers

2. Application software – the everyday programs that you use such as Microsoft Office,
graphics packages and web browsers.

3. Operating Systems
The operating system is part of the system software. All computers have an operating
system, they cannot function without one.

The operating system is a program that allows applications software to communicate with the
hardware.

Examples of operating systems are Windows Vista, Windows XP, Unix, Linux and MacOS.

An operating system has many tasks. Here are just a few of them:

• Sorting out where to store data on disk drives
• Dealing with security - user names and passwords
• Organising files and folders
• Managing data transfer from the CPU to the peripherals e.g. printer, monitor
• Deals with saving, deleting, opening, closing files



4. Utility Programs
Utility programs are part of the systems software. They are designed to do one or two
specific but vital tasks very well.

Some utility programs might be supplied as part of the operating system, others are
purchased separately.

Some common tasks carried out by utility programs are:

• File compression
• File sorting
• File renaming
• File conversion (e.g. convert a sound file to MP3)
• File repair
• Disk defragmentation (defragging)

5. Drivers
A driver is another essential piece of system software

As we said earlier, the operating system acts as a link between the hardware and software
enabling both to communicate and do their tasks.



A driver is a specially written program which translates the commands from the operating
system into commands that the hardware will understand.

Each piece of hardware e.g. printer, monitor, scanner, keyboard etc will have its own
driver. Printers from different manufacturers work in different ways, so a printer from
manufacturer A will need a different driver than printer from manufacturer B.

If you try to use a device without the correct driver, then it probably won’t work. If you do
manage to get your new printer working without installing its driver, it will probably just print
you gobbledygook!

This is what comes out of a printer with the correct driver installed: This is a printout

This is what comes out of the printer with the incorrect driver installed: Jajshu fuau&(( 89asd
8fa8s9d

Can you spot the difference?

When a new operating system such as Microsoft Vista is first released, the software
developers will have been working closely with the hardware manufacturers and so the
operating system will contain all of the drivers needed for the hardware currently on the
market. However, operating systems are only released every 3-4 years and so the operating
system will not contain the drivers for any new hardware developed after its release.

When you buy a new piece of hardware, it will usually come with an installation disk which
will load the new drivers into the operating system. Very often, you can also download the
drivers from the internet.

6. Applications Software
Software applications work through the operating system to gain access to the hardware.

A software application carries out tasks that the user is interested in doing such as writing a
letter, creating graphs, sending an email or downloading a webpage.

Application software can be classified under three main categories:

• General purpose software
• Specialist software
• Tailor made or bespoke software



7. General Purpose Software
A general purpose application, sometimes known as ‘off-the-shelf’

is the sort of software that you use at home and school.

Examples include word processors, spreadsheets, databases,

desktop publishing packages, graphics packages etc.

This type of software tries to be a ‘jack-of-all-trades’. It provides many features that the
majority of users will want e.g. formatting text, creating charts, organising tables. But it does
try to be’ all things to all people’ and so there will be a vast number of features that you may
never use e.g. statistical functions, mail merge. This makes the storage size of these
applications fairly large.

There are several good reasons for using general purpose software:

• It is relatively cheap
• It is easily available from most computer shops
• It will have been thoroughly tested so there won’t be any serious problems or bugs
• There will be lots of user support i.e. books, user guides, online help and discussion
forums on the Internet

7. Specialist Software
Specialist application packages are generally not available in shops and they often have to
be purchased directly from the manufacturer or a specialist firm.

These applications are designed to be used for specific tasks such as company payroll, stock
control systems, appointment systems, ecommerce sites etc.

The applications have not been written for a specific company. They have been developed
by a manufacturer to try to provide all of the features that they anticipate a company might
need.

Like general purpose software, there may be many features that the company does not need,
or the features which are available may not work exactly as they would like in their business.

It is possible for developers to adapt this specialist software somewhat and make it more
specific for the company needs. However, they are limited in what can be changed.



8. Bespoke Software
Although specialist software might be the answer for many companies, there will be some
organisations who find that it just doesn’t do exactly what they want or it doesn’t work with
their current systems.

In this case, they might decide to have the software system they need designed and
developed specifically for them. This is called ‘tailor-made’ or ‘bespoke’ software.

The main advantages are:

• the company will get the exact software/system that they need
• the software will work exactly how they want it to work
• the software will only have the features that they specifically need in their business.

The main disadvantages of this approach are:

• it takes a long time to develop such a system, between a few months to years
• it costs a great deal of money to develop such a system.
• the company may need to employ a team of people such as business analysts,
programmers, testers etc
• there will be little in the way of user support and online help

9. Integrated Packages
Customers who purchase a word processor often want a spreadsheet and database package
as well as a presentation package and a desktop publisher and a few others. But, each
package when purchased on its own is fairly expensive and customers may find that to buy
them all individually is more expensive than they can afford.

Some manufacturers decided to put a selection of the most popular general purpose software
together and sell it as one package at a much cheaper price than buying each package
individually.

This is called an ‘integrated package’. An example of an integrated package is ‘Microsoft
Office’ which contains Word, Excel, Access, PowerPoint and Publisher. Another example is
'Lotus SmartSuite'.

Spn year 7 notes

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