IGCSE ICT THEORY

This type requires starting at the beginning and accessing each piece of data until you reach the desired one.

This is used in applications where speed is not necessary, for example producing pay slips.

• Very fast access to data

• Data can be read directly from any part of the hard disc.

• In most of the magnetic storage devices the access speed is about 1000kb/s

• Some of the magnetic storage devices are very cheap for example floppy disks.

• Most of the magnetic storage devices store very large amounts of data.

IGCSE ICT THEORY

CHAPTER #5

Data Types

Types of Data

Data Structures

Alphanumeric and text

Logical / Boolean

The letters A to Z are referred to as text and letters A to Z plus the digits 0 to 9 are referred to as alphanumeric.

Luis is text, but Luis123 is alphanumeric.

Boolean data can only have two values: true or false. This only works if there are only two possible answers to a question.

It is mostly used when carrying out a search in a database or in the internet.

Data is often stored in files, which consist of records, which consist of fields.

For example, a company may have set up a file to include information about their employee in the following format:

reference number/name/date started/department

CHAPTER #2

FILE

Numeric Data

Date Data

RECORD

It can be in two forms: Integer (whole numbers) or real (containing decimals). For example, 5546 is an integer but 55.46 is real.

Integers include the number of people in a room, the number of dogs in a house, etc. Real numbers include temperatures, heights, etc.

RECORD

Date can be written in many forms:

• dd/mm/yyyy
• dd/mm/yy
• dd.mm.yy
• yyyy-mm-dd

All of the above are written in numbers, but dates can also be written as the full word or three letter abbreviation:

• dd mmmm yyyy - 18 June 1999
• dd-mmm-yyyy - 18 Jun 1999

Input and Output Devices

FIELD

CHAPTER #1

FIELD

OUTPUT DEVICES

MONITORS

TFT MONITORS

They are taking over CRT monitors and they are used in laptops. The screens are made up of thousands of tiny pixels.

CRT MONITORS

#1.1 Hardware and Software

PRINTERS

Types and Components of Computer Systems

Analogue and Digital Data

They are the least expensive and are becoming rare. They use an electron gun to fire against a phosphor screen, which creates and image on the screen made of tiny dots.

ADVANTAGES

INKJET PRINTERS

-They are light

-They emit less radiation than CRT monitors

-They consume less power and produce less heat than CRT monitors

They are used to produce good quality hard copies. Printing is done bit by bit and pauses sometimes to receive more data. They are used where low output volumes are required.

ADVANTAGES

LASER PRINTERS

ADVANTAGES

DISADVANTAGES

-They produce a higher quality image than T monitors

-The angle of viewing is better than TFT monitors

They produce very high quality hard copy output. They are used in places were the volume must be kept down, or to print many pages quickly.

-High quality outputs

-Cheaper than laser printers

-Light and don't take up much space

-They don't produce harmful compounds

Hardware

-It has a bad angle of viewing

-Sometimes less definition

DISADVANTAGES

ADVANTAGES

-Slow output if several copies are needed

-Ink cartridges run out quickly

-Printing can smudge

DISADVANTAGES

-They are very fast

-Can handle large print jobs

-High quality

-The cartridges last for a long time

-Very heavy

-They get very hot

-They consume more power

DISADVANTAGES

INPUT DEVICES

-Very expensive

-Only very fast if several copies are being made

-They produce ozone and volatile organic compounds which can lead to health problems

PLOTTERS

They produce hard copies but work in a different way than printers. They are used to make big printouts such as building blueprints, the pens can be replaced with cutting tools to make large signs.

3D INKJET PRINTERS

ADVANTAGES

-They can produce huge printouts

-The print quality is extremely high

New printers that produce solid 3D models using modified inkjet technology. Thin layers of fine powder are bonded together to build up the 3D model. They are used to make prototypes that can actually work from photos, drawings etc... They will be used in the near future to make organic objects, such as human organs for transplants.

DISADVANTAGES

-They are slow

-They are expensive to buy and to maintain

Software

GRAPHIC TABLETS

-Save money as making prototypes by othe rmethods is more expensive and time consuming.

-The powders used can be ground up and reused

ADVANTAGES

They are used, for example, o produce free hand drawings that can then directly be stored in a computer.

It is the name that the physical components of a computer receive. Ex keyboard, mouse, processor...

DISADVANTAGES

-Very expensive to buy

-Slow

-The final products can sometimes be rough

PROJECTORS

ADVANTAGES

-You can modify drawings before they are input.

-Very accurate method of drawing, better than a tracker ball or mouse.

TRACKERBALL

Length, weight, temperature, etc. can take any value depending on the accuracy to which they are measured. These values are measured with an analogue device which represents physical measurement on a continuous analogue scale. For example, a thermometer represents temperature by the height of the liquid column.

For a computer to understand this data, it must first be turned into Digital data using an analogue to digital converter (ADC).

On the other hand, if the computer is controlling a device, it must change its digital data to analogue with a digital to analogue converter (DAC).

DISADVANTAGES

They receive signals from a computer, a TV or a DVD player and magnify it and project it onto a large screen. They are used to give presentations so that the whole audience can see the screen.

- More expensive than other devices, such as a mouse.

Similar to a mouse, except there is a ball on top of the device and the user controls the pointer in the screen by rotating the ball with the hand. Some tracker balls also have two buttons like normal mice. Used by disabled people.

It is the programs that control the computer system. Two types:

SPEAKERS

ADVANTAGES

-They enable many people to see a presentation

ADVANTAGES

- People with limited abilities find it easier than a mouse.

- It is more accurate than a mouse.

- They take up less space than a mouse.

They can be directly connected to the computer or built into the screen or casing. Digital data from the computer is converted into analogue form. The signal is then amplified with the speakers.

CHAPTER #6

DISADVANTAGES

DISADVANTAGES

- They are more expensive as they are not supplied with the computer.

-Images can loose quality

-They are expensive

-They can be difficult to setup

SENSORS

Systems software: programs that allow the hardware to work orrectly.

Applications software: programs that allow the user to do specific tasks.

-Used to output sound from multimedia presentations

-Used in home entertainment centers

-They can help blind people with audio output of text.

USES

LIGHT

Automatic greenhouses, automatic doors, burglar alarm systems, street lighting control...

PRESSURE

Burglar alarm systems, washing machines, robotics, environmental monitoring...

TEMPERATURE

Automatic washing machines,central heating systems, automatic greenhouses, ovens...

#1.4 Types of Computers

LIGHT PENS

PH

Automatic greenhouses, chemical processes, environmental monitoring...

HUMIDITY

They contain sensors that send signals o a computer when light changes are detected. They are used to select objects on screen or to draw.

DESKTOP COMPUTERS

Automatic greenhouses, environmental monitoring, factories where moisture levelsare crucial (e.g. manufacture of microchips, paint spraying)...

SOUND

ADVANTAGES

Made up of separate keyboard, mouse, screen and CPU

The effects of using ICT

Burglar alarm systems, monitoring liquid and powder flow in pipes...

ADVANTAGES

• Low cost as parts are sol separately
• Faster processor
• Good dissipation of any heat build up

DISADVANTAGES

-Accurate

-Easy to use

-They are small

DISADVANTAGES

• Not portable
• All parts must be connect with wires

LAPTOP COMPUTERS

ADVANTAGES

-Problems with lag when drawing on screen.

-Only work with CRT monitors.

-Not very accurate when drawing.

A computer where monitor, mouse, keyboard, etc. are all in one unit.

• Very portable
• No wires
• They can use WiFi

ABREVIATED DEVICES

DISADVANTAGES

MICR DEVICE

• They are easy to steal
• They have limited battery
• Heat dissipation is more difficult

OCR DEVICE

Magnetic Ink Character Recognition devices read characters printed in a special ink.

OMR DEVICE

Optical Character Recognition devices scan text and converts it into computer text.

ADVANTAGES

INFORMATION READERS

MAINFRAME COMPUTERS

It is a large, very powerful computer system.

-Very secure

-Accurate, no typing involved

- can still be read even if there is writing over them

Optical Mark Recognition devices detect pencil or pen marks on paper. They are used in multiple choice examinations.

ADVANTAGES

-Much faster than manually typing.

-More accurate

DISADVANTAGES

CHIP AND PIN READER

ADVANTAGES

-Very expensive

DISADVANTAGES

-Fast way of inputting answers

-Accurate, as no typing is involved

-Some difficulties reading handwriting.

DISADVANTAGES

• They can be used to do very large jobs
• They have a very fast processor
• They are capable of doing many tasks at the same time

SMART CARD READER

DISADVANTAGES

Similar to smart card readers. The card is placed in a slot in the reader and the PIN is entered by the customer.

-The marks or shadings need to be accurate

-There can be problems if the paper hasn't been filled correctly

MAGNETIC STRIPE READER

ADVANTAGES

Smart cards are like magnetic stripe cards but they use chips instead. Much more information can de stored in the chip than in the magnetic stripe.

-Very secure as the PIN type in must match the one stored in the chip.

-Lasts longer as the chip doesn't become in contact with the reader.

• They are very expensive to operate and maintain
• They can't be moved around

DISADVANTAGES

ADVANTAGES

Since the PIN is typed by the customer, they must make sure no one around them reads it.

Used to read the information on the magnetic stripe found on the back of for example, credit cards. Many cards such as credit cards or hotel room cards have magnetic stripes so these readers are very useful.

-They can be used instead of money, so you don't have to carry cash around

-The chip doesn't have to be in contact with the reader so there is less damage.

-Data is more secure in a chip than in a stripe as it is much easier to copy it from the stripe.

PERSONAL DIGITAL ASSISTANTS

DISADVANTAGES

ADVANTAGES

If the card is lost, information in the chip could be used in identity theft

- It is faster than typing the information.

- There are no errors as no typing is involved.

- The information in the magnetic stripe is safe because it cannot de read directly by a person.

- Magnetic stripes are not affected by water, oil, etc.

PDAs

ADVANTAGES

DISADVANTAGES

-It is not fooproof as they can be swapped around in items.

DISADVANTAGES

They are small handheld computers that usually come with a touchscreen that is activated using a stylus.

- The data can be lost if the stripe is damaged.

- Magnetic Stripe Readers don’t work at a distance.

#1.2 Main Components of Computer Systems

BARCODE READER

They are used to read information in the form of a bar code. Very common in shops and supermarkets.

DISADVANTAGES

• They can be used anywhere because of their size
• They are very light and more portable than laptops

ADVANTAGES

-Faster than typing

-Safe, as can't be read directly

- Automatic stock control

They are:

• It is difficult to enter text quickly
• They have very limited capabilities due to the software and operating system used

CONTROL DEVICES

There are also:

Input devices: keyboard and mouse

Output devices: monitor and printer

Secondary storage devices: DVD and hard drive

BUZZERS

WHAT ARE THEY USED FOR?

MOTORS

#1.3 Operating Systems

• Used in microwaves and cookers to tell the operator when cooking process is complete
• Used in burglar alarm systems to warn if intruders are present

WHAT ARE THEY USED FOR?

Processor and interna memory devices: central processing unit (CPU), random access memory (RAM) and read only memory (ROM)

• In industry, to control robotic arms
• They operate fans, disk drives and DVD drives in computers

General tasks of a typical operating system

HEATERS

WHAT ARE THEY USED FOR?

• To control input, output and storage devices
• Supervise the loading, running and storage of applications
• Dealing with errors that occur in application programs
• Maintaining security security of the whole computer system
• Maintaining a computer log (which contains details of computer usage)
• Allowing communication between user and computer system (user interface)

• Used in automatic washing machines, cookers and heating systems
• Used in automatic greenhouses to control temperature

LIGHTS

WHAT ARE THEY USED FOR?

• Used for security lights
• Used to control lighting conditions in greenhouses

CHAPTER #4

Computer Networks

Many computer systems are now connected together to form a network. They are often set up to share resources such as printers or software.

TYPES OF NETWORKS

NETWORK DEVICES

Network Hubs

Routers

Routers are used to connect LANs together and also connect them to the internet. They are used to forward messages between computers in different networks.

BUS NETWORKS

RING NETWORKS

They are hardware devices that can have several devices/computers connected to them . its task is to receive data from any of the ports and send it out of all the ports. Each computer/device will receive the data.

Every computer in the networks is connected in a ring, including the server. Data is transmitted around the wing and each computer only removes the data that is relevant to it.

Each computer or device is connected to a common central line. Data travels along this line until it reaches the computer or device that requires it. The ends of the lines have terminators to prevent data bounce which could cause interferences.

ADVANTAGES

• Ring networks work well under heavy loading.
• It is possible to create really large ring networks.

DISADVANTAGES

• It is easy to add a new computer or device to the networks.
• If one computer or device fails it does not affect the whole network.
• It requires less cabling than for example a star network, therefore it costs less.

• If there is a fault in the wiring between two computers then the whole network will fail.

Bridges

DISADVANTAGES

• If there is a fault in the central line then the whole network fails.

They connect one LAN to another LAN. They decide whether a message from a user is sent to another user on the same LAN or to one on a different LAN. It examines the message and passes it on.

HTTP Proxy Servers

Switches

TREE NETWORKS

STAR NETWORKS

This is a type of server that acts like a buffer between a WAN (like the internet) and a LAN. The server passes on the service requests to the internet and then passes back the requested pages.Any page retrieved from the internet is stored so that if another computer requests it is available immediately.

They are like hubs but more efficient in the way they distribute their data. Each device connected to it has a media access control (MAC) that identifies it uniquely. It learns that X is always connected to port 4 and will only send its corresponding data to port 4. This means that the network traffic is only sent to were it is needed.

Each computer is connected via a central hub or switch. Data is sent to the hub which then sends out data along every cable to each computer or device.

It has a central line with a series of star networks connected to it. The server is also connected to the central line.

It has the advantages and disadvantages of bus and star networks.

ADVANTAGES

• If one computer or device fails, the rest of the network is unaffected.
• It is easy to expand the network.

DISADVANTAGES

• If the central hub breaks down, then the whole network crashes.

CHAPTER #3

CHAPTER #7

Storage Devices and Media

The Ways in Which ICT is Used

Backing up data means the copying of files onto a safe place in case of a problem with the main storage device.

Serial Access

Direct Access

The computer uses a key field to calculate where the data has been stored. This is much faster than Serial Access.

It is used in applications where speed is vital, for example to control a chemical plant.

PORTABLE HARD DISK DRIVES

OPTICAL STORAGE MEDIA

MAGNETIC STORAGE

CD-ROM AND DVD-ROM

They are like fixed hard disk drives but are usually connected to the computer with a USB port. It can be disconnected to be used in different computers.

Magnetic storage media and devices store data in the form of tiny magnetized dots. These dots are created, read and erased using magnetic fields created by very tiny electromagnets.

The are read only memory (ROM), they can not be written over and can only be read. The data is stored as a series of pits (binary 1) and lands (binary 0). The pits and lands are read with a soft laser that reflects differently off a land than a pit and is interpreted as a 1 or a 0.

ADVANTAGES

• The data access time and transfer rate is fast.
• They have large memory capacities.
• They can be used to transfer information between computers.

ADVANTAGES

• They hold much more data than floppy disks.
• They are less expensive than hard disk drive systems.

DISADVANTAGES

• It can get damaged if it is dropped or not shut down correctly.

• The data transfer rate and data access time is slower than in hard disks.

• Data can be altered by magnetic fields, dust, mechanical problems

• Gradually lose their charge over time - data lost

• Hard disks eventually fail which stops 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.

CHAPTER #8

Systems Analysis and Design