June 2012

Ben Smith

Unit 3 GCSE ICT

Encoding data this simplifies the way in which

data is represented, e.g. M for male and F for

female

The time taken to find an item of data is known as Speed of access.

On storage devices such as memory sticks or external hardrive data can be retrieved almost

instantly, much quicker than that of manual methods such as looking through a phone book or

rooting through a filing cabinet of records.

The access time for RAM, or Random access memory is measured in nanoseconds.

The access time for secondary storage devices such as hard drives are measured in milliseconds

Key word: RAM (Random access memory)… Where operating system applications and data in

current use is kept so that it can be accessed by the processor quickly.

Retrieving data from immediate access store (e.g. RAM) is much quicker than retrieval from

secondary devices such as CD ROMS, to make retrieval quicker the CD ROM data is loaded onto the

RAM.

Remember: be sensible to validate, check to verify

• Checks for transmission erros

• Checks for transcription errors e.g. omission and spelling mistakes

Data Validation: Making sure that data is sensible

• Checking that data obeys to certain rules (e.g. month value no higher than 12)

• Checking that there are no errors in data entry

Data Verification: Checking the data entered is correct

Computer Simulations

What is a computer simulation?

A model of a real system

Examples are pilots in a flight simulator and lorry drivers in a driving simulator

File storage When files are stored on a storage device, they have to be given a name, each file is also give a file extension. What is the purpose of a file extension?

To show what type of data it is To show what applications package will open that particular file

The details which will be saved with the file include: size of file, date and time the file was made and the application it can be opened with. Examples of file extensions...

Doc (a word document) Xlsx (excel book) PDF (portable document file) Accdb (access database)

Data compression Problems can arise when saving data...

Storage space can be filled quickly Larger files can take longer to load Transmission of larger files can be slow

Data compression makes files smaller whilst being stored or transmitted, these then have to be decompressed before they can be opened again, this has a number of advantages and disadvantages...

Advantages Disadvantages

A smaller file size means that less storage space will be taken up

Precision of data can be lost

Much quicker data transmission It is not always possible for files to be returned to an uncompressed state

Files have to be de compressed in order for them to be opened again.

Saving sound files .WAV (wave), this gives maximum quality. However it takes a lot of space and cannot be compressed .wma (windows media audio) this type of file can be compressed without loss of quality on some versions .mp3, this has a lower bit rate meaning that quality may be compromised as opposed to higher bit rated file types, however they can be compressed and are standard in personal listening devices such an MP3 player.

Saving video files… Video files can be compressed by converting them into files that compare one frame with the next

and only sending data about the changes between them. The standard format for a compressed

video is MPEG. Mp4.

Saving Folders…

Groups of files can be saved as a single compressed file, but it will need to be de compressed before

the files can be used. One method of compressing files is to zip them (the file extension is .zip)

Going online- Web Software

A web browser searches for the websites internet address or uniform resource locator (URL).

A URL begins with the type of internet resource being used so that the browser can tell what

protocol is being used. Examples of this…

‘HTTP’ Hyper transfer protocol, a common protocol in an internet address

‘HTTPS’ Hypertext transfer protocol over Secure Socket Layer (SSL). This means that the data is

encrypted.

‘FTP’ File transfer protocol, used for downloading files over the internet

After the type of resource, the URL consists of a unique address such as www.google.co.uk

Comparing Websites…

When comparing websites look at:

House style, pages should have similar colour schemes, fonts, layouts & logos

Audience, what is the website aimed at?

Size, How detailed is the website?

Techniques, Look for use of colours, pictures, sounds, interesting hot spots, buttons, roll

overs, forms, searches and other features used.

Presentations…

Examples of features used in presentations (e.g. PowerPoint):

Text

Image

Sound

Video

Animation

Slide transition

Hyperlink

Hotspot… an area on the screen that will respond to a click of the mouse button

Button

Navigation Bookmarks… Links that are saved so that you can jump back to them any

time if the presentation is linked to the internet they can be urls to external slides or

pages (e.g. a youtube video in a PowerPoint presentation)

Presentation Software

Advantages Disadvantages Easy standardisation of slides Relies on a computer

Easy to edit Training may be required to use the

computer

Order of slides can be changed easily Computers can have breakdowns

They can include many special effects Heavy and expensive equipment such as a

projector required

Presentations can set to run

automatically

Difficult to annotate slides during a

presentation

Hardware

Key word: Multimedia… When text, sound, images, animation and video are combined together to

give either;

Multimedia Hardware…

For a multimedia system you need:

Good sized high resolution screen

Good quality speakers

Fast processor

High spec graphics card

Large hard drive

Dvd or blue ray play

Touch sensitive input devices such as touch pads

A microphone for voice input devices or music and other sounds

Output devices for

multimedia systems…

1. Screen

2. Speakers

1. A production such as

a slideshow

presentation

2. An interactive

production such as a

computer game or quiz

Te

Storing compressed multimedia files

Advantages Disadvantages

Less storage space is used so more data can be recorded on a given device

Quality and detail could be lost

Files are smaller so transmission time is quicker Files required to be decompressed before being used again

Files are standardised to recognisable formats It is not always possible to de compress a compressed file to retrieve the original

Storage Techniques Text •generally as either .doc or .docx

•.txt, this is a generic format which can be read by any text compatible programme

•Generally small file sizes

•American Standard Code for Information Interchange (ASCII). where each character is changed to a number

Storage Techniques Images •Bitmap (.bmp) where each pixel for the file is recorded

•Good quality images generally need to be compressed due to large file sizes into file types such as .jpg or .gif formats

Storage Techniques Sound •Sound can be stored as an analogue file where a physical change records the music such as using grooves on records.

•The sound waves can be digitised so all sounds are represented in uncompressed binary form such as .wav

•compressed sound files such as .mp3 are popular because they are quicker to transmit and take up less storage space than uncompressed files

Video

Videos consist of many frames each of which can be saved making a large file

Compressed video files record only the changes between the frames as in .mpg files

Bitmap Graphics…

Made up of pixels (coloured squares(

The larger the dots the more pixels required to maintain quality

Sometimes known as raster images

Vector Graphics

Consist of mathematical equations that describe the relative distance of a point from the

point of origin

Components are described in length, thickness & colour

Vector Graphics are better than Bitmap because…

1. They can be enlarged without the quality being compromised

2. Less storage space required (smaller file size)

3. Smaller file size also means that they are quicker to load

Images

Images have layers, the more layers the more memory the slower they will be to load

Creating & Manipulating still images, Standard tools used…

Using the Computer…

The Operating System…

A set of programs that control the running of computers. The operating system has to load before

any applications can be run which is why computers can take time to boot.

Functions of an operating system…

1. Loads & runs programmes

2. Makes the best use of immediate access store (RAM, random access memory)

3. Handles the inputs and outputs from devices

4. Deals with interrupts e.g. signals from the printer that its out of paper

5. Manages the security of the system

Examples: Microsoft Windows, Apple Macintosh

Process Control in Industry

Process control is an example of a real time system, data received from the sensors by the

controlling computer is immediately analysed using a stored program and this allows the system to

respond immediately to any variations in the processing.

The output from the system will change the data the sensors are reading so this new data is

processed which in turn will change the outputs again, this cycle is endlessly repeated and is know as

a feedback system.

Process control advantages:

Little human interaction required

The process can continue 24 hours a day every day

Automatic and immediate response to problems

Safety for the workers is improved

Process control disadvantages

Expensive equipment and computer hardware needs to be purchased and installed

It has created some unemployment

Some problems may arise which require human decisions that the system cannot deal with.

Expert Systems…

An expert system is a system that takes the place of a human expert. A database of knowledge

can be searched and deductions made on the basis of the search results

An expert system simulates the knowledge and skill of an expert

It has a large database of knowledge which can be interrogated

It has an inference engine which allows the computer to make deductions based on the facts

that have been input and the data in the knowledge database

Expert system advantages:

The knowledge in the database can be far more than a human is capable of

remembering

An expert system should never get facts wrong

An expert system lives meaning that it has the opportunity to evolve over time

Some people would prefer to enter personal data into a computer rather than discuss it

with a doctor

Expert system disadvantages:

Some people prefer the personal touch rather than dealing with a machine

Expert systems are expensive to install