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ICT IGCSE THEORY

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Andres Soler

on 2 April 2014

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Transcript of ICT IGCSE THEORY

Advantages
What are barcodes?
Barcodes
Disadvantages
How to read barcodes
A barcode is an optical machine-readable representation of data relating to the object to which it is attached. Originally barcodes represented data by varying the widths and spacings of parallel lines. Later they evolved into rectangles, dots, hexagons and other geometric patterns in two dimensions (2D). Although 2D systems use a variety of symbols. Barcodes originally were scanned by special optical scanners called barcode readers; later, scanners, desktop printers and smartphones.
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Barcodes eliminate the possibility of human error.
A barcode scan is fast and reliable
It takes less time than entering data by hand.
They are very cheap.
They can be customized depending on
their purpose
If you want to know the advantages of barcodes you will need to scroll in lette "n"
Damaged Labels
Bar code readers cannot read labels that are wrinkled, dirty or smudged.

Training
The need to train employees, which can be a significant issue if the business is large.
Printer Requirements
Dot matrix and ink jet printers cannot print high-quality bar codes.
Scroll in letter "n" to know the disadvantages of barcodes
Barcode Readers
The earliest and cheapest barcode scanners are built from a fixed light and a single photosensor that is manually "scrubbed" across the barcode.
Like the keyboard interface scanner, USB scanners are easy to install and do not need custom code for transferring input data to the application program. On PCs running windows the HID interface emulates the data merging action of a hardware "keyboard wedge", and the scanner automatically behaves like an additional keyboard.
Barcode scanners can be used in Google's mobile Android operating system via both their own Google Goggles application or 3rd party barcode scanners like Scan. Nokia's Symbian operating system features a barcode scanner. With BlackBerry devices, the App World application can natively scan barcodes and load any recognized Web URLs on the device's Web browser. Windows Phone 7.5 is able to scan barcodes through the Bing search app.
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Note that bar codes are made up of both white and black lines. The white spaces in between the black lines are part of the code.
Understand that there are four different thicknesses to the lines. Henceforth, the skinniest line will be referred to as "1," the medium-sized line as "2," the next largest line as "3." and the thickest is "4."

Recognize that each UPC bar code begins and ends with 101 (thin black, thin white, thin black). In the very middle of the bar code, you will notice two thin black lines sticking down between the numbers. The thin white between them, as well as the thin whites to either side, make up a 01010. Each UPC bar code has 01010 in the middle.
Recognize that each digit, including the small numbers that begin and end the bar code, has its own unique four-line set. 0 = 3211, 1 = 2221, 2 = 2122, 3 = 1411, 4 = 1132, 5 = 1231, 6 = 1114, 7 = 1312, 8 = 1213, 9 = 3112. Notice that the line colors are reversed after the center-line: The lines of the digits to the left are white/black/white/black whilst to the right they are black/white/black/white. This provides some error checking and allows the reader to know the direction in which it is scanning a code. It is also crucial so that the bar code ends with a bar rather than a space. So, actually, each digit has two codes.
So, the bar code above whose first two digits are 03 would start out "10132111411". Broken down this is "101-3211-1411" where 101 marks the beginning of the bar code and 3211 marks the digit 0 .
Networks
Most computer systems are connected together to a form which is known as a network.
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Local Area Networks
A local area network (LAN) is within one building, not over a large geographical area. It consists on a number of computers and devices. One of the hubs will be connected to a router and modem to allow the LAN to connect to the internet, By doing this it becomes a Wide are network (WAN)

ADVANTAGES
Sharing of resources
Communication between users
There is a network adminstrator

DISADVANTAGES
Easier spread of viruses
Printer queues
Slower acces to external networks
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Ring Networks
Scroll in letter "e"
Every computer is connected to a ring, including server. Data is transmitted along the ring.

ADVANTAGES
Work well under heavy loading
Possible to create large networks

DISADVANTAGES
If there is a fault in the wiring between two computers, the whole network will fail.
Adding a new device or computer can be difficult
Bus Networks
Each computer is connected to a common central line. Data travels along this line until it reaches the required device.

ADVANTAGES
Easy to add a new computer
Does not affect the network if one computer fails

DISADVANTAGES
Difficult to isolate any fault
The network fails if the central wire fails
Star networks
Each computer is connected via a central hub or switch.

ADVANTAGES
If one computer fails, it does not affect the rest of the network
Problems on the network are easy to identify
Easy to expans the network

DISADVANTAGES
If the central hub breaks down the whole network crashes
Tree Networks
It has a central line that connects a series of star networks.The servr is also connected to the central line.

ADVANTAGES
Network is not affected if one computer fails.
Problems in the network easy to spot
Network easy to expand

DISADVANTAGES
If the central line breaks down, the whole network cashes
Wireless LANs
Similar to LANs but there are no wires. Access points are connected into the wired networks at fixed locations.Limited use because it has a small range of 30 to 50 metres.
Scroll in letter "A"
Scroll in letter "e"
Want to know more?
Try scrolling in letter "e"
IF you want to know about tree networks scroll in letter "e"
Chapter 8
Chapter 7
IGCSE Theory I.C.T.
Chapter 1
Chapter 4
Chapter 6
Chapter 2
Chapter 3
Chapter 5
Systems analysis and design
Observation
Questionnaires
Interviews
Looking at existing paperwork
Description
Advantages
Disadvantages
Involves watching personnel using the existing system to find out exactly how it works.
The analyst obtains reliable data
It is possible to see exactly what is being done
It is relatively inexpensive method
People are generally uncomfortable being watched and may work in a different way
If workers perform tasks that violate standard procedures, they may not do this while being watched!
Description
Advantages
Disadvantages
Involves sending out questionnaires to the work force and to customers to find out their views of the system and to find out how key tasks are carried out
The questions are answered quickly
Inexpensive method
Individuals can remain anonymous
Allows quick analysis of the data
Often, number of questionnaires returned is low
Questions are inflexible, since they have to be generic
There is no way to clarify a vague or incomplete answer to a question
Description
Advantages
Disadvantages
Allows the analyst to see how paper files are kept, look at operating instructions and training manuals and check the accounts.
Allows information to be obtained which was not possible by any of other methods
Analyst can see for themselves how paper system operates
Allows analyst to get some idea of the scale of the problem, memory size requirements, type of input/output devices needed
Can be very time consuming
Expensive method due to the analyst's time
Advantages
Disadvantages
Description
Involves a one-to-one question-and-answer session between the analyst and employee/customer.
Gives opportunity to motivate the interviewee into giving open and honest answers to analyst
Allows analyst to probe for more feedback from the interviewee, also easier to extend a question
Possible to modify questions as interview proceeds and also ask specific questions
Good method if analyst wants to probe deeply into one specific aspect of the system
Can be time consuming
Expensive, due to use of analyst time
interviewee cannot remain anonymous
TYPES OF COMPUTERS
A large, very powerful computer system.

Uses
To run commercial applications such as banking and insurance, where huge amounts of data are processed every day.

Advantages
Can have several CPUs.
Very fast processor speeds.
Can support very fast processor speeds and multiple operating systems
Huge amounts of storage capacity.
Can do large jobs which require a large memory and fast processor time.

Disadvantages
Have to be permanently housed in a large room, and can not be moved around.
Very expensive to operate and maintain
Mainframe computers
A computer that can almost fit into a hand and is a smaller version of a laptop.

Advantages
Low weight.
Low power consumption.
A processor that does not generate too much heat.
Easy to transport.

Disadvantages
No optical drives.
Very small keyboard.
Limited battery life.
Netbooks
A type of computer where the monitor, keyboard, pointing device and processor are all together in one single unit.

Advantages
Very portable, since all components are all together in one single box.
No trailing wires.
Can take full advantage of “Wi-Fi”.
Can link into any multimedia system.

Disadvantages
Easy to steal.
Limited battery life.
Some components might be too small to use comfortably.
Heat dissipation is more difficult.
Laptop computers
It is made up of separate monitor, keyboard, mouse and processor unit. “Personal Computer” usually refers to computer systems which are IBM-compatible.

Advantages
Spare parts and connections tend to be standardised, and have a low cost.
Desktops usually have a better specification for a given price.
The large casing allows good dissipation of any heat build-up.

Disadvantages
Not portable because it is made up of separate components.
All components need to be hooked up by wiring.
Because it is not portable, you need to copy files when you want to do some work elsewhere.
PC/Desktop computers
Small hand held computers that usually come with a touch screen that is usually activated using a stylus. Data is entered by using a keyboard that appears on the touch screen.

Advantages
Can be used anywhere because of their size.
Very lightweight and are very portable.

Disadvantages
Difficult to enter text quickly.
Very limited capabilities due to the software and the operating sistem used.
Personal digital assistants
Input devices
Input devices
Webcams
Uses
Used to enable conferencing to take place
Advantages
Can be left on constantly
Allow people to keep in contact with each other without the need to travel
Disadvantages
Very limited features, picture is often of poor quality
They need to be connected to the computer
Input devices
Sensors
Uses
Different types of sensors: temperature, pressure, light, sound, humidity/moisture and pH
Advantages
Readings are continuous
Readings are more accurate than those taken by human operators
Disadvantages
Faultyu sensors can give spurious results
Input devices
Input devices
OCR readers
Uses
Used to process passports and identity cards
Advantages
Errors reduced since there is no manual entry
Much faster data entry than system than manually keying in data
Disadvantages
Not very accurate
Has difficulty reading handwriting
Input devices
OMR devices
Uses
Used to read questionnaires and multiple-chioce examination papers
Advantages
Very fast way of inputting the results of a survey
Disadvantages
The forms need to be carefullyt designed to make sure the marks are correctly positioned
Input devices
Barcode readers
Uses
Used in supermarkets and shops where goods are marked with a barcode
Advantages
Faster than keying in data manually
Fewer mistakes are made
Barcodes enable automatic stock control
Disadvantages
The system isnot foolproof
Input devices
Scanners
Uses
Used to scan in documents
Old valuable documents can be scanned
Advantages
Much faster and more accurate than typing again a document
It is possible to recover damaged documents
Disadvantages
Quality can be limited, depending on the scanner resolution
Input devices
Chip and PIN readers
Uses
Used where payments are made using cards
Advantages
More secure payment system than a magnetic stripe or requiring signature
More robust system than a magnetic stripe readers
Disadvantages
Need to be careful that no one reads your PIN
Input devices
Smart card readers
Uses
Used in ID cards, electronic passports and driving licenses
Advantages
Reduce need to carry cash
Disadvantages
If lost, information could be used in identity theft
Input devices
Magnetic stripe readers
Uses
Used for travel systems, security cards, credit and debit cards
Advantages
Data entry is faster than a keyboard
No errors
Prevent acces to restricted areas
Disadvantages
If damaged, data is lost
Input devices
Joysicks
Uses
Used in video/computer games
Used in simulators
Advantages
Control is in three dimensions
Disadvantages
More difficult to control the pointer than with a mouse
Input devices
Remote controls
Uses
To remotely control devices
Advantages
Can use them from any distance
Disadvantages
The signal can be easily blocked
People with limited hand movement find them difficult to use
Input devices
Trackerballs
Uses
Opening, closing and minimising software
Grouping, moving and deleting files
Advantages
People with limited hand movement find it easier to use than a mouse
Disadvantages
Not supplied with the computer
Input devices
Touchpads
Uses
Opening, closing and minimising software
Grouping, moving and deleting files
Advantages
Rapid navigation through applications
Can be sed without a flat area
Disadvantages
Difficult to “drag and drop” with them
More difficult to control the pointer than with a mouse
Input devices
Mice
Uses
Opening, closing and minimising software
Grouping, moving and deleting files
Advantages
Rapid navigation through applications
Disadvantages
Difficult to use without flat area
Input devices
Numeric keypads
Uses
To only enter numbers
Advantages
Easy to carry around
Faster to enter data than standard keyboards
Disadvantages
Difficult to enter text with them
Difficult to use due to small keys
Input devices
Keyboards
Uses
Input data into applications softwarre
Advantages
Fast entry of text into a document
Easy use
Disadvantages
Users with limited arm use find them difficult to use.
1. Analysis
2. Design stage
Input Forms
Reports
Produce Flowcharts
Pseudo Codes
Hardware/Software requirements
Verification/Validation
Range, Length, Type, Format, Limit, Presence, Consistency, Check digit
3. Development and Testing
Data Type
Length of Field
Key Field
How Data is Link
Linking Different Parts of the Design Stage
Testing: Normal
Extreme
Abnormal
4. Implementation
Direct Changeover
Expert Systems
These systems have been developed to mimic the expertise and knowledge of an expert in a particular field.
Some Examples are...
Diagnosing a person's illness
Diagnostics(finding foults in a car engine,finding fauults on a circuit board,etc)
prospecting for oil and minerals
tax and financial calculations
chess game
indentification of plants, animals and chemical compounds
road scheduling for delivery vehicles
How To Set Up An Expert System
The Ways in which I.C.T is used
Communication applications
Newsletters
Websites
Multimedia presentations
Music scores
Cartoons
Flyers
Posters

A newsletter is a regularly distributed publication generally about one main topic that is of interest to its subscribers.
definition
Definition...
Data Types
Types of data
There are several data types found in most computer systems:
Logical/boolean
alphanumeric/text
Numeric
Date
A field that contains a Yes or No (True or False). Boolean data may be stored as one byte or as little as one bit (1 or 0).
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