ICT REVISION - THEORY

ADC - Analogue to Digital Converter

The data sent by sensors to the computer is normally analogue data. As computers are digital devices thay cannot process these information. So always an ADC is used to convert analogue signals to digital signals to enable the computers to process it.

Backup

Backup is a copy of files kept on an alternative medium to prevent data loss in case anything happens to the original. Usually Backup copies are kept away from the location of the computer.

Bar Code Reader

barcode readerBarcode Reader is an automated input device most commonly used in super markets. Each product has been given a barcode and a barcode scanner is used to input product details into the computer at point-of-sale (POS)

Using a BarCode scanner to read barcodes is faster and more accurate than entering those details using a keyboard.

Batch Processing

Batch processing is a type of processing in which all relevant data are collected, input to the computer together by an operator and then processed in one go rather than in number of parts.

Example:

  • Electricity bill preparation
  • Water bill preparation
  • bank processing cheques
  • processing credit crd bills

DAC - Digital to Analogue Converter

Computers are digital devices and actuators (output device in a control system) are analogue devices. So a DAC is used to convert digital signals to analogue signals, when a computer wants to communicate with actuators.

Data collection - Methods of data collection

  1. Questionnaire: A questionnaire is distributed among employees for them to fill it out and return.
  2. Interview: If the analyst wants to know what is going on in an organization the obvious thing to do is to ask the people who work there.
  3. Observation: The system analyst can learn a massive amount from simply watching what is going on in the organization.
  4. Documentcollection: (Following a paper trail through the system) - finding out what happens to a document at each stage. Also a lot can be discovered about an organization by examining the documents that it uses.

Data collection methods - Advantages and Disadvantages

  1. Questionnaire
    Advantage: It is much less time consuming, because the workers can fill in at the same time.
    Disadvantages: Questionnaires may not be taken seriously by workers.
    Analyst cannot change questions half way through.
  2. Interview
    Advantages:
    Questions do not have to be fixed in advance.
    Analyst can change the questions according to the answers.
    Disadvantage:Interviewing takes a lot of time.
  3. Observation
    Advantages:
    Very useful because no planning is necessary.
    It does not involve working with other people.
    Disadvantage:
    People tend not to behave in a normal way if they know they are being watched. Point a camera at someone and you will understand what it means.
  4. Documentcollection
    Disadvantage:
    The documentation is often difficult to understand, so it may be necessary to ask someone in the organisation to explain it.

Encryption - Advantages & Disadvantages

Advantages:

  • Unauthorised users won’t be able to understand data
  • Only person/computer with key can understand data

Disadvanatages:

  • The data can still be deleted.
  • If the person encrypting the data accidentally deletes the encryption key the data will be unreadable

GPS

GPS 

ThGlobal Positioning System (GPS) is the satellite navigation system that provides location and time information in all weather conditions. It is used for navigation. Global Positioning System consists of 27 Earth-orbitting GPS sattellites. GPS device receive signals from these satellites and works out the exact location and present it on a pre-installed map. There should be unobstructed line of site to atleast four of the sattellites for the GPS device to calculate its location.

GPS - Applications

  • Used in cars to calculate routes and navigation
  • Used by walkers to locate position on hills, mountains or forests
  • Used by runners to calculate the distance run
  • Used in ships for navigation
  • Used in tracking lorry fleets
  • Used in tracking aircrafts

GUI - Graphical User Interface

GUI is a type of interface provided by operating systems. A GUI operating system provides Windows, Icons, Menu and Pointer for the user to interact with the computer.

Windows, Macintosh, Linux, Solaris, etc are examples for GUI operating system.

Another kind of interface provided by operating system is Commandline Interface.

Implementation - Methods

  1. Direct changeover
    The company stop using their old system and start using the new system.
  2. Parallel Running
    Company uses its old system and new system together for a certain period of time and if the new system is successful they stop using the old system.
  3. Phased Implementation
    Suitable for systems that are made up of smaller sub-systems. Implementation is done by computerising each sub-system one at a time
    A part of the system is computerised and the remaining sections continue with old system.
    In the second phase one more section is computerised and so on.
  4. Pilot Implementation
    Pilot implementation is to try out the new system only one part of an organisation.
    If successful adapt it to the whole system.

Internet - Why some companies don't want their workers to access internet during the work

  • They may waste time playing games, going social networking, , online shopping, banking, surfing, etc
  • They could access undesirable sites
  • They could download viruses or malware
  • Could make the company succeptible to hackers.

Magnetic tape - Advantages and Disadvantages

Advantages:

  • Magnetic tape is less expensive per unit volume of memory
  • Tapes are easier to store
  • Tapes are easier to remove from premises if needed

Disadvantages:

  • Tape is slower to access data than magnetic disc
  • Tape requires a special drive
  • Tape is slower to access data than magnetic discs

Modelling - Advantages of using computer models rather than real things

  • Some situations might be dangerous whereas models are less dangerous
  • Cost of building real things is expensive
  • Real things may waste raw materials used for building them
  • In computer models it is easier to change data and variables
  • Some extreme conditions which can't be tested in real life can be tested using models

Modelling - Advantages of using computer models rather than real things

  • Some situations might be dangerous whereas models are less dangerous
  • Cost of building real things is expensive
  • Real things may waste raw materials used for building them
  • In computer models it is easier to change data and variables
  • Some extreme conditions which can't be tested in real life can be tested using models

Modelling - Uses of modelling

  • For making simulations
  • creating mathematical models
  • Scientific models
  • Civil engineering models
  • Financial models
  • Flight/pilot simulation/training
  • Large scale chemical experiments
  • Design of fairground rides
  • Traffic control
  • Building fire simulation

Online banking - Advantages to the Bank

  1. Fewer staff required so bank can save a lot of money in wages
  2. Less actual cash handled – fewer robberies
  3. Have access to a wider customer base
  4. Fewer branch offices needed – less spent on rent and utilities
  5. Less money spent on security staff

Online Banking - Drawbacks to the Bank

  1. High initial cost of hardware and software to set up the online banking facility
  2. Need to train the staff
  3. System maintenance will be very expensive
  4. Loss of personal contact with the customers

Online Banking - Software and Hardware required

  • Modem/Router :- To connect the computer to the internet
  • Browser:- To access the bank’s website/to search on different websites/allow access to internet
  • ISP (contract) :- To access the internet/to provide internet services
  • Telephone line :- To connect the router to the internet

Online banking - Transactions that can be done from home

  1. Customers can pay bills
  2. Customers can create standing orders
  3. Customers can order a new PIN for their ATM
  4. Customers can stop a cheque
  5. Customers can see recent transactions
  6. Customers can apply for a loan
  7. Customers can view to up-to-date bank statements
  8. can check account balances
  9. Can transfer funds between the customer’s different accounts or to a third party
  10. Can modify their personal details

Pendrives - Advantages

  • Pen drives are portable - easier to carry than CDs
  • Most computers have USB ports not all have CD drives
  • Pen drives store more data than a CD

Pendrives - Disadvantages

  • Pen drives are more expensive than CDs
  • Pen drives are easier to lose than CDs
  • Virus can spread easily through pendrives

Pharming

Pharming is done by installing malicious code on a PC or server that redirects a genuine website’s traffic to the fraudulent website.

Phishing

Phishing is done by sending email that invite you to go to a website or asking for your personal details like account details, username, passwords, credit card details, etc

Relational Database

Relational database is a database that contain two or more tables of data connected by links, called relationships.

Robots - Advantages to the workers of introducing robots rather than using using humans to manufacture cars

  • Safer environment for workers
  • Don’t need to lift heavy loads.
  • Fewer manual tasks to do
  • Cleaner and healthier working environment
  • Can lead to re-training to improve skills
  • More technical jobs available

Robots - Disadvantages to the workers of introducing robots rather than using humans to manufacture cars

  • Can lead to unemployment - many employees will lose their job
  • Deskilling can occur

 

De-skilling: In factories there will be many skilled employees. They have acquired those skills from years of experience. When computers are introduced to do their job, no one learn those skills and gradually there will be no one with those skills. This situation is called as de-skilling

Sensors

Sensors are automated input devices, they can detect physical quantities like temperature, pressure, light, etc and input to computers. They are commonly used as input devices in control systems.

Examples of sensors

 Sensor What it Detects 
 Temperature sensor  Temperature
 Pressure sensor Pressure 
 Humidity sensor  Humidity / Dampness 
 Proximity sensor  How close or far something is 
 Sound sensor   Sound
 Movement sensor   Movements nearby
 Push switch If something is touching or pushing 

Social Networking sites - Features of social networking sites

  • Allows users to connect and communicate with friends
  • Allows user to send messages to more than one friend anywhere in the world
  • Can search for people who you’ve fallen out of touch with
  • Can connect with people with similar interests
  • Can arrange meetings/events/visits to cinemas/theatre with whole group
  • Can share photographs to whole group or people
  • Can create and share personal profile
  • You can follow actions or thoughts of others
  • Can write comments on other’s posts
  • Can have privacy controls
  • Can lead to cyber bullying

Spreadsheets - Features of spreadsheet that make it suitabale for modelling

  1. spreasheets can use text as well as numbers
  2. It can perform automatic calculations
  3. Can perform 'what-if' analysis
  4. It can replicate formulae
  5. Can have absolute and relative references
  6. Can creat graphs/charts

Spyware

Spyware is a software that gathers data from computers without the user's knowledge.
It monitors and records all key presses.
It sends this information back to the hacker who sent it out.
Usually spywares are used to gain personal details of users

Technical Documentation - Contents

Technical Documentation will contain:

  • The overall design of the system
  • The test plan and test data together with the expected results
  • Any restrictions or limitations on the use of the software
  • The format for input data
  • The format for printed output
  • Top-down design – the breaking down of the problem into smaller problems or modules
  • Program listing
  • Data dictionaries
  • Details of hardware requirement of the system
  • Details of software requirement of the system
  • Algorithms and pseudo-codes
  • System flowcharts
  • Information about the file structure used
  • Details of validation routines used
  • Details of the variables that have been used.

User Documentation - Contents

The User Documentation will contain:

  • How to install the system
  • How to run the program
  • What sort of hardware and software was used
  • What sort of input is needed, how to input it
  • What sort of output is produced
  • Some sample outputs
  • Some examples of successful operation
  • Meanings of error messages
  • What to do when something goes wrong (Troubleshooting guide)

Videoconference - Hardware & software required

  • Router - used to connect to internet.
  • Web cam - used for inputting faces of participants
  • Microphone - used to inut voices of participants
  • Network card - to connect computer to network
  • Speakers - used to output the voices of participants
  • Big screen - to output faces of participants
  • Videoconferencing software needed to link participants

Videoconferencing

Video conferencing is a method of visual and audio communication between people at different locations locations, using internet.

Videoconferencing - Disadvantages

  • Takes time to learn new technology
  • It costs money to train people to use this new technology
  • Difficult to have international meetings because of time differences
  • High initial cost of buying hardware and software.
  • Equipment can break down/power cuts can stop conference
  • Poor strength of signal or loss of connection will interrupt the meeting
  • Loss of personal or social contact between people

Virus

Virus is a harmful piece of computer program or script that replicates itself, attaches itself to files and transfer itself from computer to computer through network.

Virus - Harmful effects of computer virus

  • Virus can corrupt or delete files or data
  • It can corrupt or erase the contents of the hard disk
  • It can completely fill the hard disk or memory making it unusable or slows down operations
  • it makes software, operating system unusable.

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