Year 10 Computer Studies

Computer Studies Notes

Communication Systems

Communication Media

Cable Links:

Type	Description
Coaxial Cable	Cheap Wire surrounded by plastic Used for TV and VCR Not easily affected by interference
Fibre Optic Cable	Most expensive of all Not affected at all by surroundings Can transfer large amounts of data Thin as human hair Made of glass bundled together which transfers light
Twisted Pair Wire	Cheapest Used for telephone lines Pairs of insulated copper wire Easily affected by outside interference Limited data capacity

Non-Cable Links:

Type	Description
Microwaves	Carries voice and data Transmits in a straight line Can be interfered with It is a signal Has no cables
Satellite	Very expensive Can be used worldwide Errors and interference are rare compared to microwaves Signals may be intercepted

Analog and Digital

Type	Description
Analog	Telephone lines
Digital	Computer Format Also known as binary/ASCII

 

Computer (Binary/Digital) to modem converted to Analog (Telephone) converted by modem to Computer (Binary/Digital).

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MODEM:

Abbreviation if modulation (D/A) and demodulation (A/D)

They convert DIGITAL to ANALOG and ANALOG to DIGITAL

Networks

NETWORK TOPOLOGIES:

The arrangement of computers, cabling and peripheral devices in a LAN

LAN:

(Local area network) Two or more computers linked together within a small geographical location

WAN: (Wide area network) Computers linked together over a wide geographical location (worldwide) eg. The Internet

FILESERVER:

Sorts/Stores files within a network

PRINTSERVER:

Sorts, stores and processes print jobs at required time

NODE:

Any device attached to a network

• Why do we network computers?
• Share applications
• Share files
• Share peripheral devices
• Communication
• Good security and safety

 

LAN- NETWORK TOPOLOGIES

Type	Description
Bus Network	A connection of many nodes to a single network cable that is called the bus Nodes can be added or removed without breaking If the cable breaks, the whole network will stop working Only one message can be sent at any one time or the network connection will break Ethernet is needed (works with bus network only) to avoid collision It listens to buzzing signals on the lines so the other nodes know that they shouldn’t send data and wait instead Rarely, but if two computers send at the same time and an error occurs, the Ethernet returns with a message telling both computers that there was an error and they should try again
Star Network	Has a hub (central computer) Doesn’t have to be in a circular shape (can be arranged in rows) Only network where data doesn’t have to travel through all computers to get to its location Hub has the ability to see which computer the data should be sent to The only time the network would break is if the hub breaks Cable or node breaking won’t break the network
Ring Network	Data goes around the ring in ONE direction Crashes can still happen so token rings (virtual envelopes) are used There has to be free token rings to send the data in or the computer will have to wait Token rings are used to detect errors and to send messages back if there is an error Although there has to be free token rings, if the destination of a token ring is the same as what one computer wants to go to, more data can be added Data travels from computer to computer

 

PROTOCOLS

A set of rules that govern the communication between two computers

- Handshaking occurs when protocols are confirmed

ASCII

: American standard code for information interchange

• Two types of protocol
• 7 bit ASCII

• 7 bits in a byte (sends just text)

8 bit ASCII

• 8 bits in a byte (sends multimedia and software)

• One character = One bit

In order for handshaking to occur, ASCII type, parity and stop bits must be confirmed

Parity Types

• Odd
• Even
• None

Stop Bits

• 0
• 1
• 2

Hardware and software

Two types of hardware

Output

• data that is displayed

• Examples: Printer, monitor, speakers

Input

• data that is entered

• Examples: Scanner, keyboard, mouse, mic

Two types of software

Network Operating Systems

• Allows for applications to be performed

• Examples: Windows, Mac OS, Linux

Applications

• Performs specific tasks

• Examples: Ms Office, Photoshop, Winamp

Storage

Two types of storage:

Primary

• Non-Portable

• Eg. Hard Drive

Secondary

• Portable

• Eg. Floppies, CDs, DVDS, Zip Disk, Flash

Transmission Modes

Two types of transmission modes

• Serial

• ---

• Each bit reaches at a different time
• Is slow

Parallel

• ---

  ---

  ---

  g

• 7 or 8 simultaneously
• Each bit reaches at the same time
• Is faster

Algorithms

• Purpose of Algorithms:
• List of steps which when followed in order, will solve a particular problem or carry out a particular task in a finite amount of time

• Key PSEUDOCODE terms:
• BEGIN

• IF… THEN
• WHILE
• CASEWHERE
• ENDIF
• ENDWHILE
• ELSE

END

• Key FLOWCHART diagrams:

 

• Condition

 

• Process

 

• BEGIN and END

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• Depicts flow of data

 

 

Q-Basic - Graphics

Dimensions of Screen 12 resolution

640px ACROSS (x-axis)

480px DOWN (y-axis)

Qbasic commands on every new program:

• CLS
• SCREEN 12
• Pi=3.14

To draw a LINE

• Line (x,y)-(x,y),c,bf

• Eg: Line (100,120)-(100,380) [vertical line]

To draw CIRCLES, ARCS, and ECLIPSES

CIRCLE (x,y),r,c,s,e,a

• R=radius
• C=color
• S=starting point
• E=ending point
• A=aspect

 

 

• To locate text
• Locate (x),(y)

To write text

Print “TEXT GOES HERE”

PSET

Pset (x,y)

PAINT

Paint (x,y), c

DRAW

Draw “r00d00l00u00″

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• Comments

REM

‘

The Internet and the World Wide Web (Plus website design…)

WWW

Stands for World Wide Web

• It is a wide area network that enables people to communicate

Browser

An application which assists in viewing webpages

HTML

Stands for Hypertext Markup Language

• Hypertext refers to links

URL

Stands for Uniform Resource Locators

HTTP

Stands for Hypertext Transfer Protocol

• It is the usual protocol used for transferring files and data

Website Design codes

• Basic Tags

<html> - The required tag - </html>

<body> - The tag that shows the information - </body>

• bgcolor="COLOR" – changes color of the background
• background="URL" – changes background to an image

<p> - Paragraph spacing - </p>

<br> - Line break –

<h1> to <h6> - Headers - </h1> to </h6>

<center> - Center text - </center>

<hr> - Horizontal rule –

<!—comment goes here. It can only be viewed by looking at the source –>
Formatting Text

• <b> - Bold text - </b>
• <strong> - Strong text - </strong>
• <big> - Big text - </big>
• <em> - Emphasised text - </em>
• <i> - Italicised text - </i>
• <small> - Small text - </small>
• _{- Subscript text -}
• ^{- Superscript text -}
• <pre> - Preformatted text - </pre>
• <code> - Computer code- </code>
• <kbd> - Keyboard text - </kbd>
• <tt> - Teletype text - </tt>
• <samp> - Sample - </samp>
• <var> - Variable - </var>
• <address> - Address - </address>
• <abbr title="WORD"> - Abbreviation - </abbr>
• <acronym title="WORD"> - Acronym - </acronym>
• <q> - Quotation - </q>

Monitoring and Control Systems

Features of monitoring and control systems

Monitoring and control systems examples

:

• Entertainment systems
• Room environment (heating, cooling and lighting systems)
• Washing machines, dishwashers and microwave ovens

• Systems

refer to the whole procedure of devices


• Subsystems

are divisions in systems which are individual actions for the devices to follow.

• The parts of a monitoring and control system are:

• Sensors (INPUT)
• Collect data about the surround environment
• Main types of sensors

are:

Temperature	Mechanical temperature sensors rely on the expansion and contraction of metals when they are cooled. (EG. Thermostats and thermocouples) Can be used to throw a switch Electronic temperature sensors depend on the changing properties of certain materials at different temperatures. Produce weak signals and need amplification to make them useful. EG. Thermistors.
Optical	Based on the photoelectric cell, a thin wafer of silicon material that produces electricity when exposed to light. Detects color and type of light.
Chemical	Separates and identifies the different chemicals in a sample or measures the amount of light or electricity that could pass through it Eg. Spectrometer
Motion	Detect sudden changes in movements
Pressure	Use motion sensor attached to a barrier which moves when pressed by a fluid or gas to detect movement energy.

• Processor
• Uses the data to perform calculations and make decision under the control of the software

• Effectors (OUTPUT)
• Carry out the physical work of the system

• Commonly used effectors

are:

End effectors	Tools such as drills and grippers that are attached to the end of robotic arms.
Switches	Responsible for switching large amounts of electrical power on and off. Rely on relays to perform the switching work
Electric motors	Most accurate are stepping motors, hydraulic (oil) and pneumatic (air) are others.
Tools	Industrial robot arms used on assembly and production lines usually have tools such as welders, drills, cutters or grippers as end effectors.

• The basic elements of a monitoring and control system are:

• Hardware-

sensors, processors and effectors


• Software -

control the processor

• Feedback

is the process or using the data collected from outputs to make decisions on how it operates

• An interface is what occurs at the boundary between two systems

• In monitoring and control systems the interface is at the connection between a computer and a sensor, and a computer and an effector

• Common examples of digital signals are:

Computers

Mobiles

• Common examples of analog signals are:

Telephones	Joysticks
Speakers	Thermometers

• A

/D converters convert analog signals to digital

• D

/A converters convert digital signals to analog

• The role of software is to:

Accept data inputs	Process the data
Make decisions based on the data	Produce results (outputs)

• Data inputs come from sensors

• Outputs can be the action of effectors

• The QUALITY OF THE OUTPUTS produced by a computer by a computer system DEPENDS ON the quality of the CONTROLLING SOFTWARE as much as it does on the ACCURACY of the data given to the system

• Software control languages/ways

:

specialised control languages used in industrial system	Intelligent systems that can learn tasks from a human trainer
Systems that use programming languages commonly found on home PCs

• Theoretically control a computer’s input and output devices
• Practically, some languages are better designed for the task than others

• A robot is

any machine designed to perform tasks automatically and with the minimum of external assistance.

• There are six classes of robots:

Class 1- Manual Handling Device (Teleoperator)	Controlled by a human operator. Operator uses a control device to direct EVERY movement of the machine. Are not true robots.
Class 2- Fixed Sequence Robots	Automated machines which perform a set sequence of steps over and over again. Cannot be easily changed to perform other tasks. Not true robots
Class 3-Variable Sequence Robots	Automated machines that can be altered to perform any sequence of preset tasks. They are ideal for use in assembly and production lines where the products and types of jobs can quickly change.
Class 4- Playback robots	Can learn new tasks by copying the actions of a human operator through human controlling the robot like class 1 but Class 4 can play back actions. Then eventually perform without further human supervision. First general purpose machines
Class 5- Numerical Control Robots	Are programmed rather than taught. Thus tasks performed sooner and with greater accuracy. More flexible
Class 6- Intelligent Robots	Have the ability to make decisions about the tasks that they are performing. Uses sensors to locate and identify the objects that they are working with. More versatile and independent.

• Robotic devices can be used to help the disabled by identifying nerve signals and then the control motors built into artificial limbs.

• System designers
• Design monitoring and control systems

Technicians

Repair and maintain them

Engineers

Turn the designs into working systems

Programmers

Create specific software for them

Scientists

Develop new technologies for use in monitoring and control systems

• The term robot originates from the Czech word- slave worker. It was used to describe a mechanical device that replaces human workers.

 

 

• Law of robotics purposes
• Reassure to humans that they were no threat
• Prevent robots from being misused

• The Law of robotics were:

• May not cause harm to humans
• Obey the orders from humans unless conflicts with Law 1
• Protect its own existence unless conflicts Laws 1 and 2
• Consider overall good of humanity to be of great importance than just one human

Databases

What is a database?

Software which organises and stores data

Two types of databases

Prepared or closed databases

• Contain information about a specific subject

• The information can be accessed and read, but cannot be altered

Empty or flexible databases

• Allow data to be entered or altered
• Usually referred to as database management systems

• That is, the user decides on the topic and the type of information to be stored

Databases are divided into:

Files (eg. The database itself -SQL)

Records (eg. The database table -SQL)

Fields (eg. A form entry)

Characters (eg. An alphanumeric character like q)

Creating a database involves

Collecting data, database design, database input, database output and evaluation of the database

Data can be viewed in

Label form (one record only)

Table form (more than one record, with fields extending across the screen)

Query

Retrieval of information