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IGCSE ICT revision cards for chapter 1, 2, 3 They're the most repetitive in papers <3
software
general term used for programs that control the computer system and process data
it can be application software or system software
difference between RAM and ROM
RAM
temporary memory so data can be changed
volatile memory - contents lost when power lost
can be written to and read from
stores data, files part of os currently in use
ROM
permanent memory so data cannot be changed
non volatile memory - contents retained even when power lost
can only be read from
what does an operating system (OS) do
OS - type of system that enables the user to communicate with the computer
controls input/output devices and backing storage devices
usually involves control of data flow
supervising the loading, running and storage of applications (apps)
dealing with errors as they occur
maintaining security
keeping a computer log of events
allowing communication between computer and user
human computer interfaces
Command Line Interface
Graphical User Interface
Dialogue-based Interface
Gesture-based Interface
command line interface
requires the user to type in instructions in an exact format (and speling)
it is slow, error-prone and commands need to be learned
however, the user is in direct communication with the computer
graphical user interface
uses icons on a screen to open apps or to interact with the computer
a pointing device (eg. mouse) or finger (if a touchscreen) is used
the user is not in direct communication with the computer
dialogue based interface
uses the human voice to give commands to the computer
a microphone is used to pick up ‘key words’ spoken by the user and the computer then takes the necessary action
gesture based interface
relies on human interaction by the movement of the hands, fingers, head or feet
uses computer vision and image processing software (sensors, such as a camera, pick up movement)
advantages of AI
improvements in safety
improvements in quality
faster development of products
autonomous vehicles
disadvantages of AI
can lead to job losses and de-skilling
technology dependency
suspicion that machines are ‘taking over’
features of augmented reality
the user experiences relationship between digital (virtual) and physical (real) worlds
the user is not isolated from the real world and can still interact and see what is in front of them
can experience the AR world through special goggles or via a smartphone/tablet
virtual data and objects are overlaid
features of virtual reality
technology is able to take the user out of the real world into a virtual, digital environment
the user is fully immersed in the simulated world
users wear a VR headset which gives a 360 view of the virtual world
can be used in medicine/surgery, construction, education and military applications
uses, advantages and disadvantages of keyboard
Uses
entering data manually into a computer
typing in commands to a computer (eg. PrtScrn)
advantages
well known method
easy method of entering data into a computer
easier to carry out verification checks on data entered
disadvantages
difficult to use for people with certain disabilities
slow entry method compared to direct data entry
can lead to ailments such as RSI
uses, advantages and disadvantages of numeric keypad
uses
at ATMs to key in PIN to obtain money
at POS terminals in case the barcode on an item fails to scan properly
when using chip and PIN devices to make a card payment
advantages
faster input method than a standard keyboard when entering numeric data
easy to use input device since it involves fewer keys
disadvantages
keys can be small, making input difficult for some people
order of numbers on keypads is often not intuitive
uses, advantages and disadvantages of mouse
uses
controls the position of an on screen pointer to allow selections, open/close files and so on
advantages
faster method to choose on screen options, compared to a keyboard
only requires a small amount of desk space
disadvantages
difficult to use by people with certain disabilities
can lead to injuries like RSI
some surfaces don’t work well with mechanical mice as the mouse slips
uses, advantages and disadvantages of touchpad
uses
controls the position of an on screen pointer to allow selections, open/close files and so on but uses a flat panel below the keyboard on a laptop computer
advantages
faster method to choose on screen options, compared to a keyboard
doesn’t require additional desk space as it is integrated
no need to carry around a mouse
disadvantages
not everyone finds touchpads easy to control
certain actions can be difficult like drag and drop
uses, advantages and disadvantages of trackerball
uses
used in control rooms where desk space is limited (has more accurate control than a mouse)
used in luxury cars to select functions such as operating the GPS, allowing use of smartphone etc.
advantages
more accurate positioning of pointer on screen than a mouse
most robust and doesn’t need any special surface to work properly
requires less desk space than a mouse
less prone than a mouse at causing RSI
disadvantages
more expensive to buy than a mouse
may require certain training to use properly since it is a less well known type of device
uses, advantages and disadvantages of remote control
uses
used to control functions on TVs, Blu-ray players, hi-fi equipment and so on
advantages
can operate from a reasonable distance unlike for example a wired mouse
easy to use interface
disadvantages
easy to lose the device
batteries need replacing on a regular basis which can be expensive and is an environmental issue
the remote’s infrared signal can be blocked and may not work well if not in direct line of device
uses, advantages and disadvantages of joystick and driving wheel
uses
both are used as input devices to many gaming consoles or simulators to mimic actual controls
advantages
more realistic interface than a mouse in many games and simulations
easier and more accurate than a mouse or keyboard to control on-screen movements
disadvantages
movement can be too sensitive, making the input device difficult to use in certain applications
doesn’t allow any feedback during a simulation
uses, advantages and disadvantages of touchscreen
uses
self service tills
ATMs to enter PIN, amount of money required etc
public information kiosks
mobile phones and tablets
computer based training
advantages
fast data entry and easy to use interface
easy to expand screen size as necessary with no need to change software or entry method
easier to keep clean since the surface is glass
keyboards and keypads are more difficult to keep clean
disadvantages
limited number of possible choices available
screens can get very dirty quickly and can cause issues at fast food menu screens for eg, if not cleaned on a regular basis
screens can get scratched causing them to malfunction
uses, advantages and disadvantages of scanner
uses
scanning in paper documents and photos to be saved in electronic format on a computer
archiving of valuable old manuscripts
used to scan in barcodes at a POS using laser or LED scanners
advantages
converts written text into electronic format, allowing the text to be manipulated by OCR software and used in other documents (using a word processor)
allows damaged and manuscripts to be recovered
when used to read barcodes, the scanner becomes a DDE
disadvantages
quality of photos and text depends on the scanner resolution
scanning (particularly colour image scanning can be a very slow process
if the barcode being scanned is damaged the scanner can’t read it and a backup input method is needed
uses, advantages and disadvantages of digital camera
uses
taking photographs or videos
a data capture device (eg reading QR codes)
in dentristry to photograph teeth for later dental work
creation of virtual tours around buildings, industrial plants and so on
advantages
can take many photos compared to a traditional camera
unwanted photos are easy to delete
no need to develop photos
saving money and also gain immediate feedback about photo just taken
easy to store photos on another device or in the cloud
disadvantages
need to be computer-literate to use digital cameras effectively
some artistry is lost since brightness, sharpness exposure can all be altered by software later on
compression of images when being stored can lead to some loss quality
uses, advantages and disadvantages of microphone
uses
input speech/sound to be used in presentations, special effects, music sampling and so on
as a sensor to pick up sounds (eg in an intruder alert system, detection of liquid dripping of liquid)
in video conferencing
input device for people with disabilities
advantages
fast input method and useful for people with certain disabilities
allows the possibility of manipulating sounds in real time
can be used in voice activation systems improving safety (eg verbal commands in a car to operate key functions without the driver taking their hands off the steering wheels)
disadvantages
sound files can take up a large amount of memory unless they are compressed
using verbal input can be inaccurate (problematic if speech to text is being used)
in voice activation, you must remember keywords or certain functions of the system can be activated by mistake
uses, advantages and disadvantages of analogue sensors
uses
measure physical data from the environment and send it to a computer
many sensors exist
temperature
pressure
light
sounds
humidity
pH
advantages
readings taken are more accurate than manual methods
readings taken continuously (no vital reading would be missed)
possible to take readings in places hazardous to humans or when severe weather causes risks to human life
data gathering is automatic so it can be automatically sent to a computer
disadvantages
faulty readings can lead to to spurious results, which can be dangerous
most sensors are analogue which means they require conversion to digital using an ADC
uses, advantages and disadvantages of light pen
uses
selecting objects on a CRT screen
used with CAD/CAM software on a CRT screen
advantages
have greater accuracy than touchscreens
very small devices (useful where space is an issue)
very easy input device to use
disadvantages
problems of ‘lag’ when moving the pen on screen (especially if the screen is not clean)
currently only work with CRT screens
very dated technology
description and uses of magnetic stripe reader
description
reads information on magnetic stripes on the back of a card for eg a debit card which holds data such as acc number, sort code, expiry date and start date
it does not hold the PIN
uses
on credit/debit cards for use at ATMs or POS terminals
security cards to allow entry to a building, hotel room and so on
advantages and disadvantages of a magnetic stripe
adv
faster data entry than using a keyboard or keypad
error free due to no typing
information is more secure; data isn’t held in a human readable format
physically robust system
disadv
if the magnetic stripe is damaged. the information cannot be read
reader needs to be in close contact with card
data may not be human-readable but certain devices can read and clone data on the magnetic stripe
description and uses of contactless debit card reader
description
a read-only RFID chip is embedded in the card, containing data such as PIN, acc number sort code, expiry date and so on
a radio frequency reader can read the chip from a few cms away
uses
debit cards - allow customers to pay for items (up to a certain amt) without the need to enter a PIN
advantages and disadvantages of contactless debit card reader
adv
faster transactions as no need to enter a PIN
uses 128 bit encryption
no need for a customer to remember their PIN
retailers now don’t have access to customers’ credit/debit card information
disadv
it is possible to monitor contactless transactions if someone near you is using an RFID reading device
the max transaction is limited to a small value
description and uses of chip and PIN reader
description
the credit/debit card is inserted into the device and the embedded chip is read; a PIN is then entered that should match the PIN stored on the chip before the transaction can take place
uses
to make payments at garages, restaurants, travel agents and so on
the card reader uses and internet link (usually wifi) to contact the card issuing bank when making a transaction
advantages and disadvantages of chip and PIN reader
adv
more secure than contactless payments (needs a PIN)
the limit on spending is much higher than for contactless methods
disadv
if the PIN is accessed by a third party, the chip and PIN system is very insecure (cards can be cloned using devices attached to ATMs)
the lack of an upper limit can cause problems if a stolen card is used before it is reported stolen
description and uses of RFID readers
description
radio frequency identification (RFID) uses radio waves to read and capture information stored on a tag
the tag is made up of a microchip and antenna
(passive tags use the reader’s radio wave energy to relay back information)
uses
livestock tracking on a farm
retail
unlike barcodes, there is no need to scan - the tag is automatically read from a distance
security
RFID tags attached to goods allow supermarkets to check if articles are being removed from the store without payment
admission passes like at a theme park to gain access to rides and events
libraries
to track books out on loan
advantages and disadvantages of RFID readers
adv
tags can be read from a reasonable distance
very fast read rate
takes less than 100 milliseconds to respond
allows bi-directional data transfer
data can be sent in both directions
allows bulk detection/reading to occur
several tags can be read at the same time
unlike barcodes, it is difficult to copy or alter the data stored on RFID tags
disadv
tag collisions can occur (where data from two or more tags overlap)
radio waves can be blocked or jammed which means the data can’t be read
it is possible to hack into transmitted data and read or change it
the system is more complex and more expensive than barcode readers
description and uses of OMR
desc
optical mark recognition can read marks written in ink or pencil on a pre-printed form either by joining dots or filling in a lozenge
uses
reading questionnaire responses
automatic marking of multi-choice exam papers
automatic counting of voting choices in an election
advantages and disadvantages of OMR
adv
fast method of data input
documents can be loaded into a hopper and read automatically
more accurate than entering the data using a keyboard
removes risk of typing errors
faster to fill in a form than if using OCR
diadv
needs expensive and complex forms
forms need to be carefully designed to capture required data
OMR limits the amount of data that can be captured
problems occur if the form is not filled in correctly
often instructions need to be given on how to fill out the form
description and uses of OCR
desc
converts text on hard copy documents into an electronic format
the data can be then processed and used for example in a word processor
uses
processing of passports and ID cards at an airport security desks
converting handwritten text into a computer-usable format
automatic number plate recognition to identify cars when entering a parking for eg
digitisation of valuable, ancient documents and books
advantages and disadvantages of OCR
adv
much faster data entry than manually keying in data using a keyboard
more accurate and less error prone than manual data entry methods
if used in questionnaires, allows customer to expand on answers
unlike OMR where a customer is limited a answering set questions
diasdv
the system can’t always read certain handwriting styles
scanning of documents isn’t always 100% accurate
a complex and expensive system
description and uses of barcode readers
desc
reads barcode labels on items
barcodes are read by a laser or LED scanner/reader which scans the thickness of the dark and light lines and converts the data into a digital format
uses
in supermarkets on products, enabling automatic product information, pricing and automatic re-ordering of items; they also allow for itemised billing
in libraries to track books out on loan
safety records of equipment for eg in an office
recording the last time and electrical safety check was carried out
advantages and disadvantages of barcode readers
adv
faster checkouts and fewer errors than typing in prices using a keypad
allows for automatic stick control in many applications, such as in a supermarket, allowing for ‘just-in-time’ stocking of items
a well tried and trusted technology
disadv
not totally foolproof, barcodes can be altered or swapped by someone
barcodes are more easily damaged than RFID tags or magnetic stripe cards
if damaged or torn, barcodes may not be successfully scanned
description and uses of QR code readers
desc
quick response codes are made up of a matrix of dark squares on light backgrounds
QR codes are able to store large amounts of information/data
the codes can be read by the camera built into a smartphone or tablet
uses
in advertising, the QR code can contain phone numbers, physical addresses, website addresses and so on
can contain weblinks that are automatically activated when the codes are scanned in
can store WIFI authentication details
in augmented reality
can establish virtual online stores
the QR code is scanned by the customer’s phone and the goods are automatically delivered to their home
advantages and disadvantages of QR code readers
adv
QR codes can store much more information/data than barcodes
fewer errors than using barcodes, since QR codes allow the use of built-in error-checking procedures
easier to read than barcodes, they don’t need expensive scanners and can be read by a smartphone/tablet camera
QR codes can be encrypted which makes them more secure than barcodes
diadv
there is more than one QR code format
QR codes can be used to store malicious codes
known as attagging
when the QR code is scanned the user is sent to a bogus website or even unwittingly downloads malware
uses, advantages and disadvantages of CRT monitor
uses
cathode ray tube monitors are used in specialist areas, in applications such as CAD where a light pen is used to draw and select items on a large CRT screen
adv
they have a very large viewing angle
CRT monitors allow the use of light pens
disadv
CRT monitors are heavy when compared to modern LCD screens
tend to run very hot posing a fire risk
they consume considerably more power than LCD screens
CRT screens can flicker causing headaches and eye problems
uses, advantages and disadvantages of LCD screens
uses
liquid crystal display screens are made up of tiny liquid crystals backlit using LEDS
the main output device for computers, tablets, laptops and smartphones
where touchscreen tech is required, LCD screens are used
adv
very efficient, low power consumption
very lightweight and very thin screens
don’t suffer from image burn in
don’t suffer from flickering image
very sharp image resolution
very low electromagnetic screens compared to CRT
disadv
color and contrast from various viewing angles can be inconsistent
suffer from some motion blur/image ghosting
possible to have weak pixels that can show as either black (all fully off) or white (all fully on) dots on the screen
need backlighting (LCDs don’t produce their own light)
this can lead to variable illumination
uses, advantages and disadvantages of LED monitors
uses
light emitting diode (made up of a matrix of tiny LEDs) screen is generally used in large outdoor displays
adv
no motion lag/ghosting
no need for backlighting since LEDs produce their own light
low power consumption
LEDs can have a very long life
screens can be any size
disadv
more expensive than LCDs
can suffer from colour shift due to age and temperature
white can become yellowed
contrast ratios are not consistent
uses, advantages and disadvantages of touchscreen
uses
smartphones and tablets
ATMs (supplying cash and other bank facilities)
ticket collection machines
Note 
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