Gcse Ict Theory

8/4/2019 Gcse Ict Theory

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GCSEInformation Communication Technology(ICT)

2010/2012

Floppy Disk Drive

Visual Display Unit

Processor

DVD Drive

Speaker

KeyboardMouse

Student Name

Teacher Name

Class Set Class Code


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Knowledge of ICT Components

Definitions

ComputerAn electronic machine that receives or stores orprocesses data very quickly using a stored program.

HardwarePhysical parts of the computer system that you can

see and touch eg. Screen, printer, keyboardSoftware

Programs that make the hardware work eg.WindowsXP, Microsoft Word, Powerpoint

Peripheral DeviceAny piece of hardware which is external to theprocessor.

Input Devices Devices used to get data into the computer.Central Processing Unit

(CPU)The brain of the computer that carries out allprocesses. eg calculations

Output DevicesDevices that provide information output in a formatthat humans understand e.g. screen display andprintouts.

Backing Store Devices used to permanently store data when thecomputer is switched off. eg Hard disk, CD

ASCII American Standard Code for Information Interchange

The Structure of a Computer System

InputCentral Processing Unit

(CPU) Output

Storage


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Input Devices

An input device is a piece of hardware that is used to enter data into a computer.There are many different kinds of input devices which are either manual input orautomatic(direct data entry) input

1 Keyboard

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

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

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 sixletters on the top row of the alphabet keys.

Using a keyboard for too long can lead to healthproblems such as repetitive strain injury (RSI).To try to overcome this, different styles ofkeyboard have been developed, for example,the ergonomic keyboard. They are supposed to

put your hands into a much more naturalposition 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.


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Special Keys on a Keyboard

Function

Key

Numbered function keys at top of

keyboard are used for special pre-

programmed functions within anapplication eg F4 in Excel sets an

absolute cell address

Control

Key

Holding the Ctrl key down andpressing other keycombinations initiates differentactions. Eg Ctrl + C meansCopy

Shift Key

Holding Shift with another key

gives the second character on the

key or a capital letter for an

alphabetic character.

Cursor

Key

Cursor keys are used to move the

cursor around a document eg in

Excel these arrows are used to move

between cells.

Hot Key

Example

Pressing Shift + F10 lists the shortcut menu(NB same menu comes up with a right click)

Any shortcut key or a combination

of keys. When these are pressed a

task will be carried out. Faster forexperienced users rather than a

mouse and menus.

Questions1. What word is ctrl an abbreviation for? _____________________________2. What is the keyboard shortcut for paste? _____________________________2 Mouse

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

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

A mouse usually has two buttons, a right and left one and also a central wheel whichallows you to scroll up and down the page. The left and right buttons have differentfunctions. 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 fromwhich you can select a task. Recent versions of mice use 'optical' or 'wireless' technologyto track mouse movement.


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5 Touch Screen

A touch screen is the only device which works as both an input andan output device. You view the options available to you on the screen(output) and you then use your finger to touch the option that youhave 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 whichservice you want. You touch the option 'withdraw cash' on thescreen. You are then presented with another choice, 'how much cashdo you want to withdraw?'. Once you have chosen how much, youthen 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 atbanks, 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

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

6 Scanner

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

A scanner works by shining a beam of light onto the surface of the object that you arescanning. 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 whichcan be edited with a word processor. However, the text doesn't always get converted verywell and you could end up with a lot of mistakes.

The most popular type is the flatbed scanner. This isprobably the one that you use at school. They can scan

larger images and are more accurate than handheldscanners.


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Advantages

Flatbed scanners are very accurate and can produce reasonably high qualityimages

Any image which is digitised by the scanner can then be included in electronicdocuments

Images once digitised can be enhance 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

8 Digital Camera

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

Most digital cameras let you view the image as soon as youhave taken the picture; if you don't like what you see, it canbe deleted.

The quality of the image is dependent on the resolution orthe number of pixels. Most digital cameras range from 4 -

12 Megapixels (millions of pixels in the image). The more pixels, the better the quality andclarity of the image. Many digital cameras are now capable of taking short video clipsalong 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.

8 Graphics digitiser

Graphics digitisers are often use by graphicsdesigners and illustrators.

Using a graphics digitiser, a designer can produce


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much more accurate drawings on the screen than they could with a mouse or otherpointing device. Drawings created using a graphics tablet can be accurate to withinhundredths of an inch.

a graphics digitiser 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 menuitems

Graphics tablets are much more expensive than a mouse

9 Microphone

A microphone can be used to input sound.

The sound is detected by the microphone and an electrical signal istransmitted to the computer. Special hardware is used to convert thisanalogue 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 acomputer and then convert the speech to text.

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

10 Musical Instrument Digital Interface (MIDI)

MIDI keyboards are keyboards which are connected to a computer using a special MIDIinterface. When a person plays the keyboard the frequency, pitch and other musicalinformation is converted to digital information which can be read by the computer. Musicplayed on the keyboard can be stored on the computer. As the computer is able toproduce digital signals it can send signals back to the keyboard. Tracks made usingdifferent MIDI devices and the computer can be mixed together using computer software.This means one person can make a piece of music which includes several instruments.Special sound effects can also be added.

Advantages of MIDI1. Music can be produced by people who are not experts.2. Music can be edited easily without having to re-record the whole piece again.3. Voice tracks can be integrated with the music.


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Output DevicesOutput devices are used to provide results in a suitable format after data has beenprocessed by a computer. A softcopy is a temporary copy such as a screen display. Ahardcopy is a permanent copy such as a printout.

1 Visual Display Unit (VDU)

A typical screen measures 17 inches (43 cm) diagonally across its display area. Largermonitors make working at a computer easier on the eyes. Of course the larger the screen,the higher its cost! Typical larger sizes are 19 inch or more.

The picture on a monitor is made up of thousands of tiny coloured dots called pixels(picture elements). The quality and detail of the picture on a monitor depends on thenumber of pixels that it can display. This is called the resolution of the screen. The moredense the pixels, the better the resolution and the greater the clarity of the screen image.

Monitors come in all shapes and sizes and the type of monitor you choose will depend onseveral factors such as:

resolution

contrast

viewing angle

screen refresh rate. eg a good computer game needs a fast screen refresh

An SVGA monitor is good quality with a high resolution of 1024x768 pixels.

Cathode Ray Tube (CRT)

The CRT works in the same way as a television - it contains an electron gun atthe back of the glass tube. This fires electrons at groups of phosphor dots whichcoat the inside of the screen. When the electrons strike the phosphor dots theyglow to give the colours.

Liquid Crystal Display (LCD)

Smaller and lighter than CRTs and are used with laptops and PDAs. Desktop computersare now using LCD screens as their price has become comparable to CRT monitors. LCDsuse much less power than a normal monitor. Liquid Crystal is the material used to create

each pixel on the screen. Each tiny cell of liquid crystal is a pixel.

Advantages of LCDs Disadvantages of LCDs

Take up less space Cannot be viewed from different angles

Portable because light to carry More expensive than standard monitors

Thin Film TransistorTFT 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 theylook much nicer they take up a lot less space. They are quieter than CRTmonitors and also create less heat.


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2 Speakers

A simple output device that is essential for sound output. Pricedepends on quality but normally very cheap as high quality isonly required for specialist music applications. Multimediamonitors have speakers and/or a microphone built in.Headphones may be used when a large number of people

working in a room require individual sound output.

PrintersPrinters come in all shapes and sizes and the type of printer you choose will depend onseveral factors such as:

Quality of print required (dots per inch)

Speed of printer (characters per second/pages per minute)

Colour or black and white printing capability

Ability to print text and graphics.Size of paper A4 or A3

Type of paper that can be used eg photographic

Cost of consumables

Volume of output

3 Dot matrix printer

Also called 'impact printers' as they print by striking tiny pins against acarbon ribbon. The print head contains a grid of these pins and different

combinations of pins are pushed out to form different characters. Thismakes them very noisy as you can hear the pins striking the paper.

Dot Matrix printers are ideal when carbon copies are needed. This is because they areimpact printers and the print head bangs on the top copy of paper and the carbon papertransfers a copy to the paper beneath. They are also useful when continuous paper needsto be used to produce a large amount of documents for example invoices or bills.

Advantages of Dot Matrix Printers

Low operating costs

Carbon copies can be created by using carbonated paper.

Disadvantages of Dot Matrix Printers

Poor quality of print

Very slow printing 200 characters per second (cps)

Very noisy

Cannot produce colour copies.


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4 Ink jet printer

Ink-jet printers are very popular because they are relatively cheap to buy andoffer colour printing. These produce a better quality output than Dot matrixprinters and cost less than laser printers.

Inkjet printers fire a droplet of ink at the page by boiling it in a microscopic tube and letting

steam eject the droplet.

Colour ink-jet printers are ideal for use at home, where small quantity output is required forschool work, cards and personal stationary.

Advantages of an Inkjet Printer

Good resolution - usually 300-600 dots per inch (dpi).

Cheap to buy - the cheapest printers can be found for anything over 50.

Small - ideal for home or office.Lighter in weight than other printers

Very quiet

Can print black and white and colour on the same page.

Disadvantages of an Inkjet Printer

Slow compared to a laser printer

Colour printing is slow

Expensive consumables.

Cartridges need to be replaced more frequently than those of a laser printer.Output is ink based and will smudge if the printout gets wet

If left unused for long periods of time, the cartridges can easily dry out.

5 Laser printers

Laser printers are becoming increasingly popular, with prices droppingrapidly.

Laser printers are used in many workplaces because they are quiet,print quickly, can be stocked with a large number of sheets of paper and

produce very high quality documents.

They are either dedicated black and white printers or you can choose to use a 'colourlaser'. Black and White lasers are much cheaper to run than colour lasers. These print inthe same way as photocopiers. Powdered ink, called 'Toner' is fused onto paper by heatand pressure.

Advantages

Very high resolution - 600 to 1200 dpi (dots per inch).

High quality printouts.

Very fast: 10 -20 ppm (pages per minute) for multiple copies.


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Almost silent.

Running costs are low, although toner cartridges are expensive to replace, they lasta long time.

Disadvantages

Most expensive printer type to buy especially colour lasers.

Expensive to repair - lots of complex equipment insideCan't use continuous or multi-part stationary to create carbon copies.

Only A4 or A5 paper can be used in most laser printers (although A3 is available).

Often quite large and are heavier than other types of printer.

Printer Comparison Table

PurchaseCost

Runningcost

Quality Speed Application

Dot Matrix Cheap 50+

Cheap as

uses inkribbon

Poor withdots used to

makecharacters.

Slow200 cps

Delivery notesOr invoices

needingcarbon copies.

Ink Jet Cheap 50+

Oftenexpensive

inkcartridgesneedingreplaced

frequently.

Very good300-600 dpi

Slower thanlaser

3 ppm

Home use forschool

projects.

LaserExpensive

300+

Toner for

b/w lasts along timeso cheaperper page

than ink jet

Excellent600-1200 dpi

Fast6-40 ppm

Large

businessesand schoolsrequiring fast,good quality

printouts.

6 PlotterA plotter is a large specialist type of printercapable of printing high quality images on largersheets of paper including A3. Often paper for

plotters comes in large rolls which can be up to 2metres wide. Plotters are used to print architectsplans, maps or to print posters for advertising.

A plotter differs from a printer in that it drawsimages using a pen that can be lowered, raisedand moved across the paper to form continuouslines. The electronically controlled pen is movedaround the paper by computer controlled motors.

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


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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

Past Paper QuestionWhat type ofoutput device would be the most suitable choice for each of the followingapplications?

Producing hard copy on a home computer, including lettersand school projects.

Producing two copies of a document on carbonised paper.Producing largeplans in an architects office.Producing a warning that a bar code has not been recognised.Showing that a CD ROM drive is in use.

Past Paper QuestionJohn runs a small business. Each day he prints 100 invoices and sends out letters to customersand suppliers. He needs to buy a new printer to produce invoices and letters.

1. Give one reason why he should buy a black and white laser printer._________________________________________________________________________

2. John has over 500 customers, he wants to save his customer records so that he can keep acopy at home.

a. Name an optical storage device which would be suitable for this purpose.____________________________________________________________________

b. State the maximum capacity of the storage device you have named.____________________________________________________________________

c. Give one reason why this media is suitable for storing Johns customer records.

____________________________________________________________________

3. Nametwo software packages that you would expect to find on Johns computer system._________________________________________________________________________


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StorageExternal storage devices allow programs and data to be stored permanently.

Magnetic hard disks

Magnetic hard disks consist of a number of metal disks mounted

on a spindle. Data is stored on both surfaces of each disc. There is

a read/write head for each surface and the disks are contained in a

sealed unit to protect from dust and dirt. The disks can store aconsiderable amount of data, such as the operating system,applications software and users work. Data can be retrieved very

quickly from a hard disk.

Formatting a magnetic disk

Both floppy and hard disks store data on concentric tracks. The

disks are further divided into wedges or SECTORS. In order to

retrieve an item of data from a magnetic disc the operating systemmust know its sector number and track number. This information

is stored in a DIRECTORY. Before a floppy disk can be used itmust be FORMATTED to establish its tracks and sectors.Nowadays floppy disks come preformatted but if formatting a disk

yourself you must be wary as the process wipes any existing data from the disk.

Optical disks

1 CD-ROMs

These Compact disk read only memory devices are purchased withthe information already on them. No new information can be

saved and no existing information can be erased. A CD-ROM

holds up to 650 Megabytes of data. This makes them suitable for

multimedia applications, storing archive material, encyclopaedias,

or distribution of software by software companies. Data is burned

on to the surface of the disk by a laser beam which makes small

indentations known as pits.

2 Writeable CDS

There are two types1) CD-R (CD recordable)

2) CD-RW (CD rewriteable)

The CD-R is a blank CD that can be written to only once but can be read many times. It

is often referred to as WORM (write once read many times).

CD-RWs can be written to, erased and rewritten many times. They require a special CD-

RW drive on the computer.


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3DVD (digital versatile disk)

These look like ordinary CDs and are mainly used for entertainment purposes. The

capacity is huge compared to a CD, typically 17 Gigabytes, so the DVD is suitable for

storing full length feature films.

They require a DVD drive, which can also be used for reading CD-ROMS.

Recordable (DVD R) and rewritable (DVD RW) DVDs are also available.

Magnetic tape streamersare also referred to as digital audio tapes (DAT). Magnetic tape can store huge

amounts of data (about 60 Gigabytes) cheaply and is

therefore suitable as a backup for a hard disc. On a

network you will find a magnetic tape streamer attached tothe file server. At the end of the day a copy of the hard

disk is automatically saved to the tape in case the hard drive

fails. This is called the archive.

USB flash/pen drives

A USB drive is a flash memory card that plugs into the USB (universal serial

bus) port and come in capacities from 128 Megabytes to several Gigabytes.

These handy small storage devices are ideal for transferring data from one

computer to another.

Blu ray

Blu ray is high density optical disk storage. They are the same size as DVDsand can be double sided. It is used to provide high definition storage.

Comparing storage devices

device capacity Access speed

Flash/pen drive 128 Mb-2Gb Fast

CD 650 Mb Fast

DVD 17 Gb Fast

Tape Streamer 60 Gb Slow

Hard disk 300 Gb Very fast

Blu ray 50 Gb Very fast


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Network storage versus local storage


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MemoryThe internal memory of a computer is stored on two types of memory chip called RAM andROM. RAM and ROM are called firmware because they use microchips.

1 Read Only Memory (ROM)ROM permanently stores the booting up part of the operating system program. It is nonvolatile memory meaning its contents are not lost when the computer is switched off. Its

contents cannot be changed.

2 Random Access Memory (RAM)

RAM temporarily stores the programs and data that are currently being used. The contentsof RAM can be changed because it only stores programs and data temporarily. It is theworking memory of the computer and its contents are lost when the computer is switchedoff.Often RAM is also called Immediate Access Store (IAS). Typical RAM size is 512 MB.Larger RAM increases the speed of the processor.

3 Cache MemoryCache is fast access RAM memory placed close to the CPU and used for storing the mostrecently and most frequently accessed files. For example cache stores recently visitedweb pages allowing users to return quickly to the last page viewed. It is volatile losing itscontents when the computer is switched off. Instructions are processed faster when incache memory.Cache memory is expensive.(http://www.howstuffworks.com/cache.htm)

System Software

The Operating System is a program that enables all the hardware and software to worktogether. It also allows the user to interact with the computer system. Windows Vista andWindows Xp are operating systems. The operating system of a computer is stored on ahard disk whilst the computer is switched off.

Booting up a PC

When you switch on a computer power is sent through the circuits and the CPU loads atiny piece of software, called the boot program, from a ROM chip. This tells the CPU aboutthe types of hard drives, CD drives, memory and processors in this particular computersystem. The computer checks each of these items is functioning properly and then loads

the default operating system from the hard disk.

Tasks of the operating system1. Share processor time between applications running2. Share RAM memory between the applications running3. Manage devices connected to the computer4. Provide a user interface

Today common user interfaces are graphical and are know as GUI.
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Graphical User Interface (GUI)

A graphical user interface is often described as a WIMP application

W indows

A window shows the current task being

performed. Each window has a title bar.

Many windows can be open. The title bar

of the active window is show in blue.

I cons A picture that represents a file or acommand

M enusA list of options usually on a drop down

menu in a window.

P ointersA cursor or arrow that can be moved

about a window to make selections from

menus.


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Data and InformationData is raw facts and figures which are meaningless as they have not been processed.Information is data in a context that has meaning added, ie data that has beenprocessed.

Designing a Data Capture Form to collect data for a database

It is important that forms are well thought out and designed to collect all the necessary

data. When designing a form Leave enough space for answers

Make sure all necessary details are included

Layout should be simple and follow a logical sequence

Separate form into parts if it is to be filled in by more than one person

Make sensible use of available space

Instructions must be clear with examples where appropriate

A clear title should describe its use

Coding DataWhy code data?1. Faster to type than full words taking less time to enter data.2. Faster for the computer to perform sorts and searches on data3. Codes are often designed to be unique.

Designing Codes1. Codes should always be the same length.2. Codes must be easy to use and remember.3. Codes must not be too short.

Problems with codes1. Remembering what the code represents.2. Staff may require training to use codes.

Data InformationProcessing

Information = Data + Meaning


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Database Definitions

Direct Data Entry

1 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 whereyou 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 isreflected where a mark has been made.

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

Advantages

A fast method of inputting large amounts of data - up to 10,000 forms can be readper 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

Datafilecollection of related records stored ina table with field headings

Student File

Recordall the data connected with one itemorganised under field headings

David Brown 11V H

Field the column which holds the data Surname

Item one field in one record Brown

Key Fielda field that uniquely identifies onerecord in a datafile/table

A01234

Flat File

a database containing only onetable with all records contained inthis table under the field headings. Itcan be described as a file containingtext or data separated by commas ortabs such as in a csv file.

Student File

Relational Databasea database made up of a group oftables which are linked.

Students and Teachers

Data Redundancy Data unnecessarily duplicatedData Integrity Data that is accurate and up-to-date

Link FieldA field in two tables TeacherID in both

Teacher and Studenttable


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Disadvantages

If the marks don't fill the space completely, or aren't in a dark enough pencil, theymay not be read correctly

Only suitable for recording one out of a selection of answers, not suitable for textinput

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 markyour answers on it.

2 Optical Character Recognition (OCR)

An OCR system consists of anormal scanner and some

special software. The scanneris used to scan text on a

document or piece of paperinto the computer. The OCR

software then examines thepage and changes the lettersinto a form that can be edited

or processed by a normalword 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 wellas neat handwriting.

Although they are often up to 95% accurate, any text scanned with OCR needs carefulchecking 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


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3 Barcode Reader

Most items that are for sale in shops have a barcode printedsomewhere on the packaging.

The barcode is a series of vertical bars of varying widths that represent numbers whichcontain:

a country code, a manufacturer code and a product code.

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

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

The main advantage of using a barcode system is that any pricechange only needs to be made to the database and not everysingle product package.

Barcodes are also used on books to show the book's ISBNnumber - have a look at any textbook that you have in your bag.They are also used on library tickets so that when your ticket isscanned, the database brings up your account and any books

which you still have out on loan are displayed.

Data Types

Each field can hold only one type of data from the table below.

Data Type Description Example of aField Name

Sample Data

Text Allows anycharacter from thekeyboard to be

entered.

Surname Brown

Number Only digits Age 15Date/time Date in either date

or time formatDate of Birth 12/12/2000

Currency Adds a currencysymbol anddefaults to 2decimal places

Deposit 50.00

Logical (Yes/No) Displays a tick boxwith a tick torepresent yes

Paid Yes


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Errors when keying in data

Transcription ErrorAny data entry error created when transferring data from one source to another source.For example, keying in incorrect data from a source document into a word processor.

There are several kinds of transcription error

Type of Error Explanation Example1 Omission errors Data is left out 32 instead of 321

2 Transposition errors A specific type of copyingerror where charactersbeing typed are swappedby mistake

312 instead of 321or the as teh

3 Duplication errors Entering a character twice 3221 instead of 321

To avoid errors it is essential to check all data being entered into a computer usingdifferent methods of verification and validation.

Verification a method of checking data carried out by a person to check data iscorrect before it is processed.

Validation a method of checking data carried out by a computer to check data iscorrect before it is processed

Data verification1. Double entry

The data is keyed in twice and both versions must be identical2. Proof reading

After data is keyed in, it is read to check it has been typed accurately. This caneither be on screen or on a printout.

Data validation1. Range check

A check carried out on a number or date field to make sure the data falls within aspecified range. For example exam percentages can have a range check of

between 0 and 100.2. Presence checkEnsures that important fields are not left blankIn MSAccess set required field to yes

3. Format checkData must match a preset patternE.g a post code must have a certain combination of letters and digitsIn MSAccess use an input mask

4. Length checkEnsures data is of a specified lengthE.g. a credit card number must have 16 digits

In MSAccess set the length field for text items5. Type check

A check carried out on a number or date field to make sure the dataentered is of the correct type.


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6. Lookup checkEnsure that the data entered is one of an acceptable set of valuesSuch as Y or N, M or F

7. Check digitA check digit is an extra digit added to a numeric code to ensure that it is valid. Thisextra digit is calculated by applying a formula to the sequence of numbers.

Advantages of Databases Information is usually only stored once. Files can be linked together so that updates are automatically made to

each file that shares information The record structure can be easily altered even though lots of data has

already been entered. Access to information is fast using queries. Validation checks can be made as data is entered ensuring fewer

mistakes are made

Disadvantages of Databases

If the computer breaks down you are not able to access information. Computer files are easily copied this can be a problem therefore all

sensitive information must have protection usually by password Training is needed to use the system which can be expensive and takes

valuable time

Data CompressionData compression is used to save space or reduce download time. Data compressionsoftware is a program that is able to take a file and reduce the size of that file. Acompressed file must be decompressed before it can be used.

A zip file is one that has been compressed and when we decompress it we say we unzipthe file.

Advantage: Compressing files to a fraction of their original size makes them easier to sendor store. Winzip will compress in this way.

Disadvantage: The files must be decompressed at their destination before they can beused.

For example

Graphics can be compressed using JPEG or GIF format. Music files can be compressed using MP3 format

Video files can be compressed using MPEG format.

Data Portability

It is essential in modern computing to be able to transfer data between different softwarepackages and between different computers. To do this it is important to understand thedifferent file formats used by different software packages.


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File Formats

Abbreviation Meaning Type of file

CSV Comma separated values Text with commas between each item

RTF Rich Text Format Text as ASCII files with formatting

JpegJoint Photographic Experts

GroupStores pictures in a compressed

format

Mpeg Moving Picture Experts Group Stores video (too large for website)

Tiff Tagged image file format Stores pictures

Gif Graphics interchange format Stores a bit-mapped picture

Bmp Bit-mapped Stores a picture

txt Text Stores plain text without any formatting

Doc Document WORD document

pub Publisher Desk top publishing

Xls Excel file

Ppt PowerPoint Presentation package

Mp3 Mpeg3 Music

Mp4 Mpeg4 video

Pdf Portable document format Adobe Acrobat

html Hypertext markup language Web page


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Questions on Database1. What is a key field/primary key?

________________________________________________________

2. Give one reason for coding data that is to be keyed into a computer.________________________________________________________

3. Name two methods of data verification.1 ____________________ 2 ________________________

4. Name two methods of data validation.1 ____________________ 2 ________________________

5. Give an example of a transposition error (not the one in the notes).________________________________________________________

6. In school we have a database of all pupil records. Describe how this could be used toproduce a class list for your class set.

_______________________________________________________________________

_______________________________________________________________________

7. Why might data compression software be used on a file that is to be downloaded fromthe internet?

_______________________________________________________________________

_______________________________________________________________________

8. What is a flat file?_______________________________________________________________________

_______________________________________________________________________

9. What is a relational database?_______________________________________________________________________

_______________________________________________________________________


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Questions on Input/Output

1. What is a computer?

_______________________________________________________________________

2. What are the three stages involved in carrying out a task, either on a computer or manually?

_______________________________________________________________________3. Give an example of an input device and explain why input devices are required in a computer

system?

_______________________________________________________________________

4. Give an example of an output device and explain why output devices are required in acomputer system?

_______________________________________________________________________

5. Where are programs stored on a computer when it is switched off?

_______________________________________________________________________

6. Where does the computer store a program when it is being used?

_______________________________________________________________________

7. For each of the tasks listed name one suitable type of input device.

Transferring a page of printed text into a wordprocessing program.Reading a lottery players choice of numbers fromtheir ticket.Reading data from a bar code in a supermarket.Taking pictures of a school for its website.Typing a report into a word processing program.Pointing a clicking on options on a computer screen.

Entering a picture from a magazine onto computerto be included in a document.Recording a sample of your voice on computer.Controlling the movement of a character in acomputer game.

8. Describe how you would get a developed photograph of yourself onto a computerscreen.

__________________________________________________________________________________________________

_________________________________________________

_________________________________________________


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GCSE Information and Communication Technology

Component Percentage

Unit 1 Controlled Assessment 30%Unit 2 Controlled Assessment 30%Unit 3 Theory 40%

Theory

Knowledge of ICT Components

Data and Information

Digital Communication Methods

Applications of ICT

Practical

Assignment Title Marks SoftwareUnit 1 Database 35 Access

Unit 1 Spreadsheet 35 Excel

Unit 1 Multimedia presentation 30 PowerPoint

Unit 2 Design a computer game 40 Scratch?

Unit 2 Design a Web Site 40 Dreamweaver

Documents

Gcse Ict Theory