IGCSE Computer Science

2023

Data Representation

UNIT 1

Uses of Hexadecimal in C.S

• HTML Colour Codes
• Memory dumps
• Error messages
• IP Addresses
• MAC Addresses

3

20XX

ASCII Code

• American Standard Code for Information Interchange
• Character set- 7 bit codes
• Extended ASCII- 8 bit codes
• Every character has its own unique code
• Each character in the word is replaced by its code
• The codes are stored in the order in the word

4

20XX

Unicode > ASCII Code

• Uses 32 bit codes
• Is a superset of ASCII
• Most characters even in other languages and emojis can be represented
• Universal standard; not coded differently in other systems

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• HOWEVER, takes more space than ASCII ☹

5

20XX

Representation of Sound

• A sound wave is sampled at regular intervals
• Sample rate is the number of samples per second
• Sampling resolution/ bit depth is the number of bits used to store each sample
• Accuracy of digital sound/ recording and file size increases as sample rate and resolution increase
• Sampling done by ADC

6

20XX

Representation of bitmap images

• A bitmap image is a matrix of pixels that is converted to binary to be processed by a computer
• Colour depth is the number of bits used to store each colour
• Every pixel is assigned one colour
• Resolution of the image is the number of pixels used to represent the image
• The file size and quality increase with resolution and colour depth

7

20XX

Data Size

• – bit
• – nibble
• – byte
• – kibibyte (KiB) 1024 bytes
• – mebibyte (MiB) 1024 X 1024 bytes
• – gibibyte (GiB) 1024 X 1024 X 1024 bytes
• – tebibyte (TiB)
• – pebibyte (PiB)
• – exbibyte (EiB)

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King Mahesh Gave Ten People Eggs

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8

20XX

Calculating File Size

• Image Size= Image resolution (in pixels) X colour depth (in bits)
• Mono Sound File Size= sample rate (in Hz) X sample resolution (in bits) X length of sample (in seconds)

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• For a stereo sound file, multiply result by 2

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9

20XX

Advantages of Compression

Compression exists to reduce the size of a file

• Reduces time taken for upload/download or transfer of a file
• Less time taken for streaming a music or video file
• Lower storage costs
• Uses less network bandwidth
• Saves storage space on storage device

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10

20XX

Lossy Compression

• A file compression algorithm is used
• Redundant data is permanently removed
• Original file cannot be restored
• Some detail is lost but usually not noticeable
• Examples of Lossy Compression algorithms: MP3, MP4, JPEG

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11

20XX

Lossy Compression of a Sound File

• Discards any unnecessary sounds
• Using perceptual music shaping
• For example, removing sounds we cannot hear
• Reduces sample size
• Reduces sample rate
• Sound is clipped

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12

20XX

Lossy Compression of an Image File

• Reduces colour depth
• Reduces resolution

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13

20XX

Lossless Compression

• A file compression algorithm is used
• No data is permanently lost; the original file can be fully reconstructed
• Repeated patterns are identified
• …and indexed
• E.g RLE

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14

20XX

Data Transmission

UNIT 2

Data Packets

• HEADER
• Originator’s Address
• Destination Address
• Packet Number
• PAYLOAD
• TRAILER

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16

20XX

PACKET SWITHCING

• A large message is broken down into smaller chunks of the same size called data packets
• The packet has a header and a payload as well as a trailer
• The header contains the source IP address, destination IP address, and sequence number of the packet
• Each packet is dispatched independently
• … and may travel along different routes
• The packets may arrive out of order
• … and are reassembled into the original message at the destination
• If packets are missing/ corrupted, a re-transmission request is sent
• The router controls the route of the packet

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17

20XX

ROLE OF ROUTER IN PACKET SWITHCING

• The router examines the packet header
• It reads the IP address of the destination
• A router has access to a routing table
• … that contains information about the available hops
• … and the status of the routes along the route
• … the router decides on the next best hop
• … and sends the packet on its next hop

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18

20XX

METHODS OF TRANSMISSION

• SERIAL- one bit at a time; single channel/ wire
• PARALLEL- multiple bits at a time; multiple channels/ wires

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• SIMPLEX- one direction only
• HALF DUPLEX- both directions, but only one direction at a time
• FULL DUPLEX- both directions at the same time

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19

20XX

EXAMPLES, ADV, DISADV

• SERIAL- USB- data arrives fully synchronised so useful for long distances; slow data transmission
• PARALLEL- Internal circuits in the CPU- fast data transmission; data can arrive skewed, greater risk of interception and interference
• SIMPLEX- Computer to printer
• HALF DUPLEX- Walkie Talkie
• FULL DUPLEX- Broadband connection

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20

20XX

USB

• Asynchronous Serial Transmission
• ADV-
• Universal standard
• Backwards compatible
• Can charge mobile device at the same time
• Can be plugged in only one way
• Can automatically detect a device and install the driver
• Fast transmission speed
• Data unlikely to get skewed or corrupted
• Supports different transmission speeds

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21

20XX

USB: Disadvantages

• Wires limited to around 5m
• Older standards have limited transmission rates
• Older standards will no longer be supported in the near future

IGCSE COMPUTER SCIENCE

22

2023

USB- FOUR WIRE SHIELDED CABLE

• RED – power- (+5V)
• WHITE (Data +)
• GREEN (Data -)
• BLACK (Ground/Power)

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23

20XX

Errors during data transmission

• Data can be corrupted, lost, or even gained due to the following reasons:
• Data Interference
• Problems during packet switching
• Skewing of data

IGCSE COMPUTER SCIENCE

24

2023

Parity Check

• Checks a byte of data
• Check performed on data being received
• Counts the numbers of 1s and 0s
• Adds a parity bit to the parity byte accordingly
• Can be odd or even
• If numbers of 1s don’t match type of parity used, error detected

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• Parity blocks can be used to detect the location of the error.

IGCSE COMPUTER SCIENCE

25

2023

Checksum

• A value is calculated from the data using an algorithm
• This value is transmitted with the data
• The value is recalculated by an identical method at the destination
• The two values are compared
• If they don’t match, an error is detected

IGCSE COMPUTER SCIENCE

26

2023

Echo check

• A copy of the data received is sent back to the sender
• The data is compared to see if it matches
• If they do not match, an error is detected

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• Not a reliable method

IGCSE COMPUTER SCIENCE

27

2023

Check digit

• A value is calculated using an algorithm like Modulo-11 or ISBN 13 from the data
• It is appended to the data as the last digit usually
• The value is recalculated on data entry
• The digits are compared for error detection

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• Uses: ISBN and barcodes

IGCSE COMPUTER SCIENCE

28

2023

Automatic Repeat Requests (ARQs)

• Uses acknowledgement and timeout
• Error control protocol
• A check like parity or checksum is performed on data received
• If data received contains an error, negative acknowledgement is used/ a request to resend the data is made
• The resend request continues to be sent till data is received correctly or till the request times out
• If data is received error-free, positive acknowledgement is used
• If acknowledgement is not received in time, data is automatically resent

IGCSE COMPUTER SCIENCE

29

2023

Symmetric Encryption

• Scrambles data into a meaningless form
• Uses a single key for encryption and decryption
• Plain text changed to cipher text
• Problem- key sent with data!

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• Strength can be improved by using a longer encryption key and a more complex encryption algorithm

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30

20XX

Asymmetric Encryption

• Uses public key and private key
• E.g. If data is being sent from Ruhi to Ronak…
• Ronak will send his public key to Ruhi
• Ruhi will use this key to encrypt the message and send it to Ronak
• Ronak will use his private key to decrypt the message

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NOTE: The public and private key are mathematically linked but cannot be derived from each other, so offering better security

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31

20XX

Hardware

UNIT 3

What is the role of the CPU?

• The Central Processing Unit processes data and instructions that are input so the result can be output
• It carries out arithmetic and logic operations
• It runs the Fetch- Decode- Execute cycle to do so

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33

20XX

What is a microprocessor?

• A microprocessor is like an integrated circuit on a single microchip.
• The CPU is sometimes called a microprocessor

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34

20XX

Stored Program Concept of the Von Neumann Architecture

• The program is stored on a secondary storage device
• Instructions are fetched one at a time, one after the other
• Data and instructions are moved to the same memory/ RAM
• Data and instructions are moved to the registers to be executed

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35

20XX

Components in a CPU: ALU

• Arithmetic Logic Unit
• Performs arithmetic operations
• Performs logic operations
• Holds temporary/ interim values during calculations
• … in a register called the ACC (accumulator)

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36

20XX

Components in a CPU: CU

• Control Unit
• It sends control signals along the buses
• That manage the transfer of data and instructions within the CPU
• It decodes an instruction
• Using an instruction set

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37

20XX

System Buses

These are wires down which electronic signals and data travel.

Components in a CPU: BUSES

1. Address Bus
1. Carries an address
2. Of the next item to be fetched
3. Is unidirectional

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39

20XX

Components in a CPU: BUSES

2. Data Bus

• Carries data
• … that is currently being processed
• Is bidirectional

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40

20XX

Components in a CPU: BUSES

3. Control Bus

• Carries control signals
• Controls the actions of the CPU
• Can be unidirectional or bidirectional

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41

20XX

Components in a CPU: REGISTERS

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42

20XX

Fetch- Decode- Execute Cycle

1. The program counter contains the address of the next instruction to fetched
2. The address stored in the PC is copied to the MAR via the address bus
3. The instruction is then copied from the memory location contained in the MAR and is placed in the MDR
4. The entire instruction is copied from the MDR to the CIR
5. The value in the PC is incremented so it points to the next instruction to be fetched
6. The address part of the instruction is moved to the MAR
7. The instruction is decoded and executed

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43

20XX

Register Transfer Notation

1. MAR 🡨 [PC]
2. PC 🡨 [PC] + 1
3. MDR 🡨 [[MAR]]
4. CIR 🡨 [MDR]

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44

20XX

Factors affecting CPU performance: Cores

• Each core processes one instruction per clock pulse
• Multiple cores means that sequences of instructions can be split between them
• … and so more than one instruction can be processed per clock pulse
• Sequences of instructions can be run at the same time
• More cores reduces the time taken to complete a task

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45

20XX

Factors affecting CPU performance: Clock Speed

• Each instruction is executed on a clock pulse
• So, the clock speed dictates the number of instructions that can be run per second
• The faster the clocks speed the more the instructions that can be run per second

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46

20XX

Factors affecting CPU performance: Cache

• The cache stores frequently used instructions and data that need to be accessed faster
• It has a much smaller data access time than the RAM as it sits between the RAM and the CPU
• Uses S-RAM

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47

20XX

Instruction Sets

• An instruction set is the list of all the commands that can be processed by the CPU
• The commands are in machine code
• Opcode- informs the CPU what has to be done
• Operand- data which needs to be acted on or can point to a register in the memory

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48

20XX

Embedded Systems

• An embedded system is a microprocessor or a microcontroller within a larger system
• It performs one specific task
• E.g. lighting system, vending machine, security system, domestic appliance, cars etc.
• Don’t require an OS

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PURPOSE: Its purpose is to control the device and allow a user to interact with it

It runs on firmware and does not have additional peripherals

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49

20XX

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50

20XX

Barcode Scanner

• Red laser is shined at the barcode
• Light is called an illuminator
• Black lines absorb the light; white lines reflect
• Reflected light captured by sensors
• Correspond to different binary values
• Microprocessor interprets the data

IGCSE COMPUTER SCIENCE

51

2023

Barcode application: Supermarkets

• A barcode uniquely identifies a product
• Data about stock levels can be stored on a database
• Allows for automatic stock control; every time the product is purchased it is deducted from stock level
• Will check if the stock level is below a certain level
• Places an automatic re-order
• Can automatically update stock levels when new stock arrives
• Can check if the product is available at other locations

IGCSE COMPUTER SCIENCE

52

2023

QR Code

• A matrix of black squares on a white background
• Captured by a camera on a mobile device
• … and read using an application or software
• The illuminator is shone on the QR Code
• Squares reflect light differently
• Corner squares are used for orientation/ alignment
• Redirects
• QR code can be stored for future reference

IGCSE COMPUTER SCIENCE

53

2023

Barcode VS. QR Code

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54

20XX

Digital Camera

• Button is pushed
• Aperture opens, allowing light to pass through the lens
• Light falls on a sensor called a Charged Couple Device, converts light to electricity
• Electric current passes through an ADC to be converted to digital and be represented as an image

IGCSE COMPUTER SCIENCE

55

2023

Keyboards

• Uses switches and circuits to translate key-strokes into signals the computer can understand
• The key matrix is a grid of circuits
• All of the circuits are broken
• When the key is pressed, the circuit is completed
• The microprocessor can compare the location of the signal to a character map stored in the ROM
• Each character has a unique ASCII code value
• The key press initiates an interrupt
• So the character is added to the buffer, while it waits to be processed

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• PROBLEM- RSI= Repetitive Strain Injury
• Solution🡪 Ergonomic Keyboards

IGCSE COMPUTER SCIENCE

56

2023

Microphone

• Has a diaphragm
• An incoming sound wave causes the diaphragm to vibrate
• This causes a copper coil to move past a permanent magnet
• Induces an electric current which can be sent to an ADC to be converted to digital values

IGCSE COMPUTER SCIENCE

57

2023

Optical Mouse

• Tiny cameras take about 1500 images per second
• A red light is shone onto the surface
• The light reflects
• It is picked up by the CMOS
• … which generates electrical pulses
• … which are sent to the DSP
• The processor can work out the coordinates of the mouse based on changing image patterns
• Mirrored by screen cursor

IGCSE COMPUTER SCIENCE

58

2023

2D Scanner

• Light shone onto surface of document
• Moved across surface
• Reflected light is captured
• Passes through a series of mirrors and lenses
• Focused on sensor
• Converted to binary
• Forms a 2D digital image

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APPLICATION-

• OCR🡪 scanned document can be saved in a text file format
• Face recognition at airports

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IGCSE COMPUTER SCIENCE

59

2023

3D Scanner

• Laser shone on the object
• Measures geometry of the object
• Reflected light is captured by sensor
• Converted to binary
• Produces a 3D digital image

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• APPLICATION- CT Scanners (x rays) , MRI Scanners (radio frequencies) , SPECT Scanners (gamma rays)

IGCSE COMPUTER SCIENCE

60

2023

Touchscreens- Capacitive

• Conductive layer
• Charge spread across the screen- creates an electrostatic field
• Sensors located around the screen monitor this electrostatic field
• When the user touches the screen, the charge is transferred to the user
• … hence reducing the capacitance at that point as it is affected by the conductivity of another object
• The point of touch can be calculated

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• SURFACE CAPACTIVE- sensors places at corner of screen
• PROJECTIVE CAPACITIVE- 3D electrostatic field

IGCSE COMPUTER SCIENCE

61

2023

Capacitive Touchscreens

IGCSE COMPUTER SCIENCE

62

2023

Infrared Touchscreens

• Infrared rays sent across the screen
• Sensors located around the edges of the screen, capture the beam
• Beams form a grid
• A touch breaks the ray/ grid
• Reduces the sensor reading of two sensors
• Coordinates of touch can be calculated

IGCSE COMPUTER SCIENCE

63

2023

Infrared Touchscreens

IGCSE COMPUTER SCIENCE

64

2023

Resistive Touchscreen

• Made of multiple layers
• When touched, two layers make contact
• Circuit completed
• Point of touch calculated

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• Most used now ☺

IGCSE COMPUTER SCIENCE

65

2023

Resistive Touchscreens

IGCSE COMPUTER SCIENCE

66

2023

IGCSE COMPUTER SCIENCE

67

2023

Actuators

• A mechanical or electromechanical device such as a relay, solenoid, or motor
• Converts an electrical signal to a magnetic field producing linear motion
• Can operate a valve or a switch

IGCSE COMPUTER SCIENCE

68

2023

Light Projectors: DLP

• Uses a large number of tiny mirrors on a DMD chip
• Mirrors are arranged in a matrix/grid
• Each mirror corresponds to a pixel on the image
• Mirrors can point towards or away from the light source
• Mirrors that point towards the light source reflect the light onto a projection lens
• Colour is produced by passing the light through a colour wheel on the way to the DMD chip
• Can be used to produce an image on a wall/ screen

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IGCSE COMPUTER SCIENCE

69

2023

Light Projectors: LCD

• A bright, high intensity beam of light is sent out from a bulb or LED
• The light falls on three different chromatic coated mirrors/ dichromic mirrors
• These reflect the light at different wavelengths corresponding to its red, blue, and green components
• These fall on three separate LCD screens that use the light modulating properties of LCDs to block light or let it through
• This produces 3 monochromatic images
• They are combined in a special glass prism
• … and passed through a projection lens to create the enlarged image

IGCSE COMPUTER SCIENCE

70

2023

DLP VS. LCD

• DLP more compact
• DLP portable
• DLP has better colour contrast
• DLP runs quieter
• Better longevity
• Give shadows/ rainbow effect

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• Can have trouble lining up images
• LCD produces better colour saturation
• LCD colours more accurate, giving a sharper image
• LCD generates less heat

IGCSE COMPUTER SCIENCE

71

2023

Inkjet Printers

• Uses liquid ink/ cartridges
• Different coloured inks are mixed together to obtain the required colour
• Uses nozzles to spray ink onto paper
• Uses rollers to move the paper through the printer
• Uses thermal bubble or piezoelectric technology
• … to spray droplets of ink onto the paper
• Uses a moving print head
• Suitable for low volume, high quality output

IGCSE COMPUTER SCIENCE

72

2023

Thermal bubble and Piezoelectric Technology

• THERMAL BUBBLE
• Uses tiny resistors to create localised heat
• Causes ink to vaporize and create a bubble
• Bubble expands and forces ink to be ejected onto the paper
• Bubble collapses, creating a vacuum
• Draws in more ink
• PIEZOELECTRIC
• Tiny liquid crystal given a small electric charge
• Causes it to vibrate
• Forces ink to be ejected onto paper
• More ink is drawn in

​

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IGCSE COMPUTER SCIENCE

73

2023

Laser Printer

• Uses powdered ink/ toner
• Makes use of a large charged printing drum
• With static electricity charges
• A fuser is used to melt the ink onto the paper
• A discharge lamp is used to remove the charge from the paper
• Suitable for high-volume, high-quality output e.g. leaflets

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IGCSE COMPUTER SCIENCE

74

2023

3D Printers

• Used to produce 3D models
• Useful in CAM
• Uses tomography technology
• Object built up in thin layers
• Additive manufacturing
• Uses powdered resin, powdered metal, paper, or ceramic

IGCSE COMPUTER SCIENCE

75

2023

LED Screens

• Flat panel display
• Made of a matrix/ grid of pixels
• A grid of LEDs behind the screen correspond to the pixels
• The current applied to each LED decides its brightness
• RGB filters are used to determine the colour
• Requires no backlighting
• Very efficient and produces brilliant colours

IGCSE COMPUTER SCIENCE

76

2023

LCD Screens

• The screen is made of pixels
• … which are arranged as a grid/matrix
• Each pixel has 3 filters: red, green, blue
• Different shades of colours by mixing the three
• The screen is backlit
• Using LEDs
• The light passes through liquid crystals
• The crystals can be made transparent or opaque or anything in between
• … by changing their shape

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• Before CCFL used for backlighting

IGCSE COMPUTER SCIENCE

77

2023

LED > CCFL

• Thinner screens
• More reliable
• Uses less power
• Doesn’t need to warm up to maximum brightness
• Doesn’t give yellow tint
• Brighter light- better colour definition

IGCSE COMPUTER SCIENCE

78

2023

OLED Screens

• Use organic LEDs (carbon containing)
• Semiconductors that are very flexible
• Organic films sandwiched between an anode and a cathode
• Made of plastic screen
• Uses less power
• Needs no backlighting
• Large field of view- 170 deg
• Very thin screens

IGCSE COMPUTER SCIENCE

79

2023

Loud-speaker

• Digital sound recording passes through a DAC
• Electric current produced, amplified, runs through coil
• Becomes a temporary electromagnet, creates magnetic field that interacts with magnetic field of the permanent magnet to produce linear motion
• The iron core and attached cone vibrate
• Produces a sound wave

IGCSE COMPUTER SCIENCE

80

2023

Sensors

• Sensor sends data to microprocessor
• Through an ADC
• Microprocessor compares data to stored value
• If same, nothing done
• If higher, ______
• If lower, ________
• Signal sent to output devices via DAC
• Actuator used
• Continuous process that uses feedback

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• CAN BE USED IN MONITORING AND CONTROL SYSTEMS

IGCSE COMPUTER SCIENCE

81

2023

Primary Storage

• Storage that can be directly accessed by the CPU
• RAM – Random Access Memory
• Immediate Access Store
• Temporarily stores data and instructions, part of the OS currently in use
• Volatile
• Can be written to and read from
• Has larger storage capacity than ROM
• ROM- Read Only Memory
• Contains the start-up/ bootstrap program and the clock frequency
• Non-volatile
• Permanent
• Only be read; not editable
• Smaller storage capacity than RAM

​

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82

20XX

Backing Store

SECONDARY STORAGE IS NOT DIRECTLY ACCESSIBLE BY THE CPU AND IS NECESSARY FOR MORE PERMENANT STORAGE OF DATA

Magnetic Storage: HDD

• Has platters
• … that are spun
• Each platter is divided into tracks and sectors
• A read/write arm is moved across the storage media
• Uses electromagnets to control magnetic dots of data
• Magnetic field determines the binary value

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• PROBLEMS: latency, heating up, fragmentation

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85

20XX

Solid State: SSD

• Flash Storage
• Uses NAND/NOR technology
• Uses transistors: control gates and floating gates laid out in a grid
• … to control the flow of electrons
• Stores data by flashing it onto chips
• The electric current reaches the control gate and flows through to the floating gate to be stored
• When data is stored, the transistor value changes from 1 to 0
• EEPROM
• PROBLEM- SSD ENDURNACE (limited number of read/write operations can be performed)

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86

20XX

SSD> HDD

• Faster data access
• Heats up less
• Less interference risk due to absence of magents
• More reliable; no moving parts
• Less power consumption
• Compact

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HDD> SSD

• Longevity
• Cheaper per unit of data

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87

20XX

Optical Media: CD/ DVD

• Disk has a track that spirals out from the centre
• Has pits and lands
• Optical head shines red laser onto disk surface
• The disk is spun
• The pits reflect light differently to the lands
• The optical device can determine the binary value based off the light reflection

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88

20XX

CD VS. DVD

• CD single layer only; DVD can be dual layer
• DVD has shorter wavelength laser
• DVD spun faster
• DVD has faster data transfer rates
• DVD has larger storage capacity

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89

20XX

DVD VS. Blu Ray

• Blu Ray uses a single polycarbonate layer; DVD uses two layers
• Blu Ray uses a blue/violet light instead of red
• Blu Ray has a much higher data capacity
• Blu Ray has a secure encryption system built in

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90

20XX

Additional: DVD-R VS. DVD RAM

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91

20XX

Virtual Memory

• Virtual Memory is when the secondary storage (like HDD) is used to extend the RAM so that the CPU can access more storage space than available in the RAM itself.
• Data is swapped between the swap space on the HDD and the RAM so that only the data currently in use is stored in the RAM
• RISK: DISKTHRASHING:
• Pages are required in RAM as soon as they are moved to the HDD
• There is a continuous swapping of the same data in and out of virtual memory
• No useful processing occurs
• All processing time is used in swapping of pages

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92

20XX

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20XX

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94

20XX

Cloud Storage

• Cloud storage can be accessed remotely rather than storing data locally
• Requires physical servers and storage
• Data redundancy; same data stored on more than one server

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95

20XX

Adv. Of Cloud Storage

• Can be free
• No need for external storage device
• Can be accessed from any computer with an internet connection
• Most cloud servers have built-in backup/ disaster recovery
• Better security
• Can easily increase capacity

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96

20XX

Network Interface Card (NIC)

• Every computer needs an NIC to be connected to a network
• The NIC provides the device with the MAC address
• So that it can be uniquely identified on the network
• And allows each individual device to be connected to the network

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97

20XX

MAC Address

• Given to the NIC at manufacture
• It is a unique address
• Used to identify a device
• Set by the manufacturer
• It is static
• NN-NN-NN-DD-DD-DD
• Hexadecimal
• Manufacturer’s code and device serial number
• 48 bits

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98

20XX

IP Address

• Used to identify a device on a network
• Allocated by the ISP
• Can be used in place of URL
• Can be static…
• … meaning that is doesn’t change every time the device is connected to the Internet
• Can be dynamic…
• … meaning it can change each time a device is connected to the Internet (DHCP needed)
• IPv4- 32 bits
• IPv6- 128 bits (has colons and hexadecimal)

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99

20XX

Router

• A router sends data to a specific destination on a network
• A router can assign IP addresses
• A router can connect a local network to the internet
• A router can act as a firewall

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100

20XX

Software

Unit 4

System Software

• Provides the services that the computer requires including operating system and utility software
• Allow the hardware to run properly and allow the user to communicate with the computer
• Compilers- translators
• Linkers- allow several object codes to be combined into a single program
• Device Drivers- allows peripheral communication with OS
• Utilities
• Operating System

IGCSE COMPUTER SCIENCE

102

2023

Application Software

• Provides the services required by the user
• Allows the user to perform specific tasks
• Examples:
• Word Processor- manipulation of a text document
• Spreadsheet- Used to organise and manipulate numerical data
• Database- manipulate and organize data
• Apps
• Graphics Manipulation Software- Allow bitmap and vector images to be changed
• Video Editing Software- manipulation of videos to create new videos
• Photo Editing Software- allows manipulation of digital photos
• Control and Measuring Software- used with sensors

IGCSE COMPUTER SCIENCE

103

2023

Utilities- antivirus software

• Scans files/ computer data for viruses
• Can constantly run in the background
• Can run a scheduled scan
• Can detect automatically updating virus definitions
• Can delete a virus
• Can quarantine a virus
• Can alert the user of a possible virus
• Completes heuristic checking

​

• PROBLEM- False Positive

IGCSE COMPUTER SCIENCE

104

2023

Utilities- Defragmentation Software

• Makes individual files occupy contiguous blocks of data
• Improves data access times

IGCSE COMPUTER SCIENCE

105

2023

Utilities- Backup Software

• Responsible for making copies of files at regular intervals
• So that if data is lost/deleted or corrupted, it can be retrieved

​

​

• Ideal to have 3 copies of the file:
• Current version on internal HDD or SSD
• Local backup on portable HDD
• Remote backup on cloud

IGCSE COMPUTER SCIENCE

106

2023

Utilities- Security Software

• Manages user accounts and controls access using user IDS and passwords
• Links with other utilities like anti-virus and spyware checkers
• Protects network interfaces with the use of firewalls
• Oversees software updates
• Uses encryption and decryption

IGCSE COMPUTER SCIENCE

107

2023

Utilities- Screensavers

• Screensavers are programs that supply moving and still images on the monitor screen after a period of inactivity by the user
• Automatically logs out the user
• Allows software to run while computer is idle, for example. Virus scans and distributed computing applications

IGCSE COMPUTER SCIENCE

108

2023

Utilities- Device Drivers

• Allows peripheral hardware communication with OS
• Converts data into a format understood by the peripheral
• Uses descriptors; allows the USB bus to ask the device what it is

IGCSE COMPUTER SCIENCE

109

2023

Operating Systems

• A software that runs in the background of all computers, making it useful, and managing all its basic functions
• It provides an environment in which the applications can run as well as allows communication/ provides an interface between the user and the computer

IGCSE COMPUTER SCIENCE

110

2023

Importance of OS

• It manages a number of basic functions on your computer like file management, memory management, etc.
• It allows you to communicate with your computer using hardware devices and peripheral devices (hardware peripheral management)
• It provides the user with a human computer interface such as a GUI or CLI
• It allows for multitasking and interrupt handling

IGCSE COMPUTER SCIENCE

111

2023

OS: HCI- Human Computer Interface

• Can be in the form of CLI or GUI (WIMP)

​

IGCSE COMPUTER SCIENCE

112

2023

OS: Memory Management

• Controls movement of data between processor, virtual memory, and memory
• Allocates memory to process
• Prevents competing applications from accessing same memory location

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113

2023

OS: Security Management

• Controls user accounts and passwords
• Provides and upgrades malware checker, firewall, etc.

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114

2023

OS: Hardware Peripheral Management

• Uses device drivers to convert data to a form understood by input/output devices
• Sends data to output devices
• Receives data from input devices
• Receives and handles error messages
• Controls buffers and queues

IGCSE COMPUTER SCIENCE

115

2023

OS: File Management

• Creates files/folders
• Renames files/ folders
• Maintains directory structures
• Ensuring memory location for a file by reading it from the HDD/SSD and loading it into memory

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116

2023

OS: Multitasking

• Each of the processes will share the hardware resources under the OS’ control
• Resources are allocated for a particular time limit
• Process can be interrupted while its running
• Process is given a priority

​

IGCSE COMPUTER SCIENCE

117

2023

Running of Applications

• Applications are run by the interface provided by the OS
• The OS is run on the firmware- BIOS/ Bootloader
• Firmware is a program that provides low level control on hardware

​

• So, the app run on the OS
• The OS runs on the firmware
• The firmware runs on the hardware

IGCSE COMPUTER SCIENCE

118

2023

Interrupts

• An interrupt is a signal sent from a device or from software to the microprocessor. This causes the microprocessor to temporarily pause its current activities so that it can service the interrupt.
• Interrupts are generated when:
• There is a timing signal
• An input/output service is required
• User interaction
• Hardware fault
• Software that generates a problem

IGCSE COMPUTER SCIENCE

119

2023

Importance of Interrupts

• Used to attend certain tasks
• Ensures that important tasks are dealt with immediately
• Interrupt tells the OS attention is required
• Can be generated by hardware
• … or software
• Causes OS to temporarily pause its current task
• OS services the interrupt using the interrupt service routine
• All interrupts are assigned different levels of priority
• Enables multitasking by temporarily storing data in a buffer
• OS returns to original task once interrupt is dealt with
• E.g. out of paper message by a printer

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120

2023

A buffer is a location in the memory which temporarily stores data.

THE STATUS OF THE CURRENT TASK IS SAVED; ALL THE REGISTER VALUES ARE SAVED.

THE ISR IS INITIATED BY FEEDING THE STARTING ADDRESS INTO THE PC.

EXAMPLES

HARDWARE INTERRUPT: PRESSING A KEY ON A KEYBOARD, MOVING THE MOUSE

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SOFTWARE INTERRUPT: DIVISION BY ZERO, TWO PROCESSES TRYING TO ACCESS THE SAME MEMORY LOCATION AT ONCE

122

20XX

High Level languages

• Close to human language// uses English like words
• Machine independent
• Needs to be translated to machine code by complier or interpreter
• Problem/ logic focused
• Have built in libraries and functions

presentation title

123

20XX

Low-level languages

• Relate to the specific architecture and hardware of a particular type of computer
• Can be machine code or assembly language that must be converted to machine code

​

​

presentation title

124

20XX

Assembly Languages

• Is an example of a low-level language
• Uses mnemonic codes
• Often used to design drivers for hardware
• Can directly manipulate hardware
• Programs executed very quickly
• Has special machine-dependent instructions
• Needs an assembler to be translated to machine code

​

presentation title

125

20XX

Compiler

• Translates high level languages to machine code
• Translates the whole code at once before executing, producing an executable file that does not need to be recompiled; hence can run without the compiler installed on the device
• Can be distributed for general use
• If errors are detected, an error report is returned instead of an executable file

presentation title

126

20XX

Interpreter

• Translates high level language to machine code
• Translates the program line by line
• Stops execution when an error is detected
• No executable file is produced; interpreter is needed for execution

presentation title

127

20XX

Assembler

• Translates assembly language to machine code
• Produces an executable file
• Distributed for general use as can run without an assembler

​

NOTE: One low level language statement is usually translated to one machine code instruction while one high level language statement can be translated to multiple machine code instructions

presentation title

128

20XX

USES

• Used during the development of a program

INTERPRETER

COMPILER

• Used to translate the final program

presentation title

129

20XX

IDE- Integrated Development Environment

• A single software program used by programmers to aid the writing and development of programs
• Has features for writing, editing, translating, and testing the program.
• Features:
• Code editor
• Auto completion
• Auto correction
• Auto documenter and pretty printing
• Error diagnostics
• Runtime environment with a debugger
• Translator

presentation title

130

20XX

The Internet and its Uses

Unit 5

INTERNET VS. WWW

• The internet is the infrastructure of a worldwide collection of interconnected networks and devices
• The world wide web is a collection of many websites and webpages that can be accessed using the internet.

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132

2023

URL- Uniform Resource Locator

• A URL is a text--based address of a webpage that specifies the location of that particular HTML document on a webserver.
• It shows the protocol, the domain name, and the filename.

IGCSE COMPUTER SCIENCE

133

2023

HTTP AND HTTPS

• Hyper Text Transfer protocol- a set of rules that must be obeyed when transferring files across the internet
• When a form of security is used, like SSL or TLS, ‘s’ appears; stands for secure, tells you encryption has been used

IGCSE COMPUTER SCIENCE

134

2023

Web Browsers

• Displays webpages
• Can render/interpret/translate HTML documents
• Can interpret any embedded scripting like JavaScript
• Can provide functions like bookmarks, history, address bar, navigation arrows, multiple tabs. Cookies, hyperlinks, etc.
• Identify protocols like https, SSL

IGCSE COMPUTER SCIENCE

135

2023

Role of ISP

• Provide access to the internet
• Usually charge a monthly fees
• Determine network bandwidth
• Allow access to email
• Provide users with an IP address
• Allow web hosting facilities
• Online data storage
• Monitor users’ activities
• Provide security services

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136

2023

Retrieval and Location of Web pages

• A web browser is used
• The user types in the URL into the address bar
• The URL specifies the protocol that has to be used as well as the domain name of the server the web page is stored on
• It could be http or https, for example
• The ISP uses the domain name to look up the IP address of the company’s web server where the HTML document is stored
• The ISP can do so by referring to a database stored on the DNS
• The IP address is found and forwarded to the web browser
• The web browser sends a request to the web server
• The web server sends the website to the web browser
• It uses the client’s IP address to do so
• The document is written in HTML
• This can be interpreted by a web browser and displayed on the monitor

IGCSE COMPUTER SCIENCE

137

2023

Cookies

• When a user visits a website, the web server sends a cookie file to the web browser
• It is a small encrypted text file storing the user’s preferences
• Stored by browser on computer HDD/ SSD
• When the user revisits the website, the server requests browser for cookie file
• File sent by browser to server for access

IGCSE COMPUTER SCIENCE

138

2023

PERSISTENT COOKIES are stored on the HDD and have an associated expiry date

​

SESSION COOKIES are lost once the website session is terminated or browser closed; stored temporarily in RAM

presentation title

139

20XX

Digital Currency

• Digital Currency is one that only exists electronically
• Blockchain, in its basic form, is a digital ledger that is a time-stamped series of records that cannot be changed
• Decentralised and not backed by the government (alleviates problems of confidentiality and security)
• Security- Peer to peer network, Unique Hash Values, Proof of Work by miners
• Cryptography used

presentation title

140

20XX

A “block” in a blockchain

1. Hash value
2. Data
3. Previous Hash Value

​

presentation title

141

20XX

Purpose of Cyber Security

• Data can be corrupted or deleted either through accidental damage or malicious acts.
• There are many ways data can be intercepted leading to cyber security threats

presentation title

142

20XX

Brute Force Attacks

• Systematically trying all the different combinations of letters, numbers, and other symbols to crack the password
• Cybercriminal starts with the most common passwords and then a strong word list
• Very slow
• The longer the password used and the greater the variation of characters used, the harder it will be to crack

presentation title

143

20XX

Data Interception

• Form of stealing data by tapping into a wired or wireless communication
• Done using a packet sniffer
• For Wi-Fi networks) wardriving or access point mapping-
• Uses smartphone/laptop, GPS device, and an antenna outside a building or somebody’s house

​

Prevention: Use Wired-Equivalency Protocol (WEP) for encryption together with a firewall

presentation title

144

20XX

DDoS Attack

• Many requests are sent from multiple distributed bot-computers// useless spam traffic AT THE SAME TIME
• The requests are sent to the webserver
• The webserver becomes flooded with lots of requests
• … and fails/ cannot handle all the requests
• The website can no longer be accessed

​

Prevention- up to date malware checker, firewall

​

presentation title

145

20XX

Hacking

• Illegally gaining access to someone’s data
• Can lead to identity theft, deletion or distribution of someone’s personal information

​

• Prevention: anti-hacking software, strong passwords, firewalls

presentation title

146

20XX

Malware: Viruses

• Program/ Program code that can replicate itself
• It can cause a computer to run slow or crash
• It could delete or corrupt files
• It could fill up the storage space
• It could prevent the hardware from communicating
• It can spread to other devices on the network

​

• Prevention: Antivirus software

presentation title

147

20XX

Malware: Worms

• A standalone piece of malware that can self- replicate.
• Rely on security failures within networks to allow them to spread unhindered
• Don’t require any action from the end user

​

• Prevention- up to date malware checker, antivirus

presentation title

148

20XX

Malware: Trojan Horse

• A program disguised as legitimate software but with malicious instructions embedded in it.
• Need to be executed by end user; arrive as email attachment or can be downloaded from an infected website
• Used to install spyware and ransomware

​

​

• Prevention- don’t visit unprotected websites, anti-spyware

presentation title

149

20XX

Malware: Spyware

• A software that records the user’s activity without the user’s knowledge and sends it to a third party for analysis

E.g. keylogging software

​

• Prevention- Anti-spyware software

​

presentation title

150

20XX

Malware: Adware

• Floods an end-user with unwanted advertising
• It can hijack a browser and create its own default search requests
• Can be difficult to remove; defeats most malware checkers

presentation title

151

20XX

Malware: Ransomware

• Cybercriminal encrypts data on a user’s computer and sends the decryption key once an amount of money is paid as ransom

​

• Prevention: avoid phishing emails

presentation title

152

20XX

Summary:

presentation title

153

20XX

Phishing

• Legitimate looking emails are sent to the user
• The user clicks on a link/ attachment that redirects them to a fraudulent website
• Aims to trick the user into revealing personal data

​

• Prevention: anti-phishing toolbars on browsers, look for https and green padlock on websites, don’t click any emails until sure its legitimate

presentation title

154

20XX

Pharming

• Malicious code installed on the user’s hard drive without any action by end-user
• Redirects URL requests to fraudulent websites using DNS cache poisoning
• Aims to trick user into revealing personal/sensitive information

​

• Prevention: anti-virus, look for https and green padlock on websites

presentation title

155

20XX

Social Engineering

• Cybercriminal creates a social situation based on fear, curiosity, empathy, and trust to manipulate people into breaking their normal safety procedures

E.G. instant messaging, scareware, emails/phishing, baiting, phone calls

presentation title

156

20XX

Access Levels

• Maintains a hierarchy of access levels for different users, maintaining different rights for each user

IGCSE COMPUTER SCIENCE

157

2023

Anti-malware: anti spyware

• Based on rules (typical features) or file structures
• Can detect and remove existing spyware
• Can prevent user from downloading spyware
• Blocks access to user’s webcam and microphone
• Scans for signs of data stolen- reports to user
• Encryption of keyboard strokes

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158

2023

Authentication

• Relies on a user’s ability to prove who they are

​

1. PASSWORDS- used to restrict access to data or systems

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2023

2. Biometrics

• Relies on unique biological characteristics that belong to a human
• Fingerprint scans
• Retina scan
• Voice recognition
• Face recognition

​

USEFUL BECAUSE-

• Cannot be faked
• Cannot be recorded by a keylogger/ spyware
• Perpetrator cannot shoulder surf
• Cannot be guessed

​

​

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2023

Authentication continued…

3. Two step verification- requires two methods of authentication to verify who a user is

​

4. Automatic Software Updates – may contain patches that update the security software

5. Checking the tone and spelling of communication and URL links – beware of typo squatting

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161

2023

Firewalls

• Can be hardware or software
• Monitors and filters all incoming and outgoing traffic
• Allows user to set criteria/rules
• Checks if all incoming and outgoing traffic matches the criteria
• Blocks any traffic that doesn’t fit criteria
• Keeps a log of all traffic that can be examined
• Can block access to certain websites by creating a blacklist

IGCSE COMPUTER SCIENCE

162

2023

Proxy Servers

• Prevent direct access to a webserver by sitting in between the webserver and user
• Any attacks launched hit the proxy server instead of the webserver
• It directs invalid traffic away from the webserver
• Monitors and filters all incoming traffic/ requests
• If the traffic is valid, data from webserver sent to user
• If traffic invalid, access is denied
• Can prevent access to/ block certain IP addresses

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163

2023

Privacy Settings

• Do not track setting
• Check to see if payment methods have been saved on browsers
• Browser privacy settings – browser history, cookies permissions
• Advertising opt outs
• Apps
• Safer browsing – alerts when encountering a dangerous website

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164

2023

SSL- Secure Sockets Layer

• Request is sent to the web server to identify itself/ view digital SSL certificate
• Receives a copy of the SSL certificate sent by the web server
• Authenticates the certificate/ checks if it is trustworthy
• Sends a signal back to the web browser if certificate is authentic
• Starts transmission of data once connection established to be secure
• If website not secure, browser will display an open padlock/ warning message

​

• A TYPE OF PROTOCOL

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165

2023

Automated and Emerging Technologies

UNIT 6

An automated system is a combination of hardware and software (for example, microprocessors, sensors, and actuators) that is designed and programmed to work automatically without the need of any human intervention.

However, such systems often involve human monitoring.

General: Advantages and Disadvantages

• Reduced labour costs
• Speed and efficiency of ______
• Efficient use of __________
• Ability to __________
• Safter
• More accurate and consistent

• High initial cost
• High maintenance costs
• May not be suitable for all types of ______
• Affected by glitches/bugs/equipment failure/ interference
• Prone to hacking
• May require significant expertise in programming or technical expertise

presentation title

168

20XX

Industrial Applications

169

DCS (Distributed Control System) is a powerful computer that has been programmed to monitor and control the whole process with no human interaction required.

Industrial Applications

170

Transport Applications

171

Transport Applications

172

Agriculture Applications

173

Agriculture Applications

174

175

176

Science Applications

177

Automated Systems: General

• Uses _____ sensors
• Sends it to a computer system/ DCS/ Controller
• Compares to a database
• Role of Actuators

​

• ADV-
• Faster
• Safer
• Less expensive in the long run
• Consistency
• More efficient use of Resources

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2023

• DISADV-
• Expensive to set up
• Maintenance costs
• Unexpected situations
• Cyber security threats

​

Use of AI in automated systems

presentation title

179

20XX

ROBOTICS

Robotics is a branch of computer science that brings together the design, construction, and operation of robots.

180

20XX

Examples include factory equipment, domestic robots and drones

Characteristics of a Robot

– a mechanical structure or framework e.g. actuators

– electrical components, such as sensors

– programmable through microprocessors

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2023

ALL ROBOTS:

• Have an ability to sense their surroundings
• Have a degree of movement (may have motors, hydraulic pipes, actuators, and circuit boards)
• May have EFFECTORS (different attachments to allow them to carry out specific tasks such as welding, spraying, cutting, or lifting)
• Programmable (have a programmable controller)

​

- Mimic human functions

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182

2023

ROBOTICS IS NOT THE SAME AS AI

• Many robots don’t possess artificial intelligence (AI) since they tend to do repetitive tasks rather than requiring adaptive human characteristics.

183

20XX

SOFTWARE BOTS ARE NOT REAL ROBOTS

• Search engine bots or WebCrawlers that roam the internet scanning websites, categorising them for search purposes
• Chat Bots (programs that pop up on websites that seem to enter some form of conversation with the web user)

184

20XX

PHYSICAL ROBOTS

• Autonomous- have no direct human control
• Can replace human activity totally- requires no human interaction

INDEPENDENT ROBOTS

DEPENDENT ROBOTS

• Have a human who is directly interfacing with the robot (through a computer or control panel)
• Can supplement, rather than totally replace, the human activity

185

20XX

Robots in the INDUSTRY

• E.g) Paint spraying of car bodies, welding bodywork on cars, manufacturing of microchips, manufacturing electrical goods and automatic warehouses.
• Can be controlled by embedded microprocessors or be directly linked to a computer system
• Can be programmed with a sequence of instructions OR mimics human action by a series of sensors to generate its own sequence of instructions
• Sensors prevent them from doing “stupid things”
• Good at repetitive tasks being performed identically every time but not at specialist tasks.

​

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2023

Advantages and Disadvantages: INDUSTRY

presentation title

187

20XX

Robots in Transport

• Autonomous cars use a number of sensors, a microprocessor, a camera, and an actuator to make the vehicle successfully driverless.
• Cameras capture visual data from surroundings
• Radars and Ultrasonics – create a 3D image of vehicle surroundings

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2023

Advantages and Disadvantages: AUTONOMOUS VEHICLES

presentation title

189

20XX

TRANSPORT: Autonomous Trains

• Makes use of LiDaR- light detection and ranging
• Also makes use of proximity sensors, infrared cameras, and GPS system (Global Positioning Satellite)

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190

2023

Advantages and Disadvantages: AUTONOMOUS TRAINS

presentation title

191

20XX

Features of Unpiloted airplanes

• Increased self- testing of all circuits and systems
• Actuators to control the throttle, rudder, flaps on the wings, etc.
• Sensors to detect turbulence and ensure a smooth journey
• Sensors to automatically detect depressurisation of cabin and lead to immediate stabilisation of airplane
• Use of GPS for navigation and speed

​

presentation title

192

20XX

Advantages and Disadvantages: AUTOPILOT AIRPLANES

presentation title

193

20XX

Robots in Agriculture

• HARVESTING AND PICKING
• A more accurate way of doing labour intensive work; higher yields, faster, and reduced waste e.g. Vegebot (uses cameras to check if the crop is ripe or not and to guide an arm to cut from stalk with no damage)
• WEED CONTROL
• Uses AI to differentiate between weeds and crop
• Drone uses aerial view to produce a course of action; robots use a GPS system to follow the course of action
• Used in France to remove weeds between grape vines in vineyards

​

​

IGCSE COMPUTER SCIENCE

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2023

Robots in Agriculture

​

• PHENOTYPING
• Uses sensors (like spectral sensors and thermal cameras) to create 3D images/ models of plants to monitor health and growth in an accurate and efficient way, reporting back data to the farmer
• SEED-PLANTING DRONES AND FERTILSER DISTRIBUTION
• Drones (flying robots) produce a bird’s eye view image of the farm
• Seed planting can be done far more accurately; fertilisers can be efficiently distributed with better coverage and reduced wastage
• Also used in cloud seeding (drones adds silver iodide crystals to clouds)

​

IGCSE COMPUTER SCIENCE

195

2023

Robots in Agriculture

​

• AUTONOMOUS AGRICULTURE DEVICES
• Weeding, pruning, harvesting robots
• Grass mowers/ cutters
• Seeding Robots
• Fertiliser Spraying

​

• USE SENSORS TO GO AROUND OBSTACLES AND CAN BE PROGRAMMED TO ‘GO TO SLEEP’ IN POOR WEATHER.

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196

2023

Robots in Medicine

• Can be used to perform minor surgeries; faster, safer, less costly
• Disinfecting rooms and operation theatres
• Repetitive tasks like collecting blood samples
• Less painful
• Safer for doctors and nurses if patient has an infectious disease
• Doctors and nurses can perform more skilled work
• Monitoring Patients
• Microbots for Target Therapy
• Prosthetic Limbs

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197

2023

Domestic Robots

• Automatic Vacuum Cleaners : proximity sensors, microprocessor, actuators and motors
• Autonomous Grass Cutters
• Same set of sensors, camera, microprocessor, and actuator set as above
• Personal Assistants
• Uses connectivity to internet
• Understands voice commands and can answer questions
• HD camera to recognise a face and navigate a room

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198

2023

Robots in Entertainment

• Theme parks using robots to entertain visitors
• Creating more immersive music festivals
• Filming movies: controlling cameras, props, and actors
• Humanoid robots can be used to perform stunts in movies
• Producing special effects

​

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2023

Robot Applications: GENERAL

• What task does it perform that is human repetitive/ hazardous/ labour-intensive?
• What technology does it use- GPS, radars, etc.
• Advantages and Disadvantages

​

IGCSE COMPUTER SCIENCE

200

2023

Artificial Intelligence

AI is a branch of computer science dealing with the simulation of intelligent behaviours by computers

AI: 3 Categories

• NARROW AI: this occurs when a machine has superior performance to a human when doing one specific task
• GENERAL AI: this occurs when a machine is similar (not superior) in its performance to a human doing a specific task
• STRONG AI: this occurs when a machine has superior performance to a human in many tasks

IGCSE COMPUTER SCIENCE

202

2023

Understanding AI

• Artificial Intelligence tries to mimic the cognitive functions of the human brain

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2023

Describe the main characteristics of AI as the collection of data and the rules for using that data, the ability to reason, and can include the ability to learn and adapt

Reasoning

THE ABILITY TO DRAW REASONED CONCLUSIONS BASED ON GIVEN DATA/ SITUATIONS.

​

DEDUCTIVE REASONING IS WHERE A NUMBER OF FACTS ARE BUILT UP TO FORM A SET OF RULES WHICH CAN THEN BE APPLIED TO OTHER PROBLEMS.

ABILITY TO LEARN AND ADAPT

BY CARRYING OUT A SEQUENCE OF STEPS, THE AI MACHINE CAN LEARN AND THE NEXT TIME IT WILL KNOW HOW TO DO THE TASK MORE EFFECTIVELY AND EVEN APPLY IT TO A NOVEL/NEW SITUATION.

Examples of AI

• News generation based on live news feeds
• Smart home devices (Alexa, Microsoft Cortana, Apple Siri, Google Now, etc.)
• The AI device interacts with a human by recognising verbal commands
• It learns from the environment and the data it receives
• Device becomes increasingly sophisticated in its responses, thus showing the ability to use automated repetitive learning
• Chatbots – replicate patterns of human interactions
• Autonomous Cars
• Facial Expression Recognition

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2023

AI SYSTEMS

1. EXPERT SYSTEMS
2. MACHINE LEARNING

Expert Systems

• A computer system that mimics the decision-making ability of a human; expert systems use AI to stimulate the judgement and behaviour of a human or organisation that has expert knowledge and experience

IGCSE COMPUTER SCIENCE

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2023

Applications of Expert Sytems

• Oil and mineral prospecting
• Diagnosis of a patient’s illness
• Fault diagnosis in mechanical and electronic equipment
• Tax and financial calculations
• Strategy games, such as chess
• Logistics (efficient routing of parcel deliveries)
• Identification of plants, animals, and chemical/ biological compounds

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2023

Advantages and Disadvantages of Expert Systems

• High level of expertise
• High accuracy
• Consistent results
• Have the ability to store vast amounts of ideas and facts
• Can make traceable logical solutions and diagnosis
• Can have multiple expertise
• Very quick response times
• Unbiased reporting and analysis of facts
• Indicate the probability of the suggested solution being correct

• Users need training to work the system correctly
• Expensive to set up and maintain
• Give very ‘cold’ responses
• Only as good as the information/ facts entered into the system
• Misconception that it is infalliable

presentation title

210

20XX

presentation title

211

20XX

User interface

• Way in which user communicates with expert system
• Dialogue boxes, command prompts, etc.
• Yes/No answers that use feedback/ are based on answers to previous questions

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212

2023

Inference Engine

• Main processing element
• Acts like a search engine, examining the Knowledge base for data that matches the queries
• Problem solving part of the system- makes use of inference rules in the rules base
• Tries to find a matching object from the knowledge base

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2023

Knowledge Base

• Repository of facts
• Stores all the data about a particular area of expertise gathered from a number of expert sources
• Collection of objects and attributes

IGCSE COMPUTER SCIENCE

214

2023

Rules base

• Set of inference rules
• Used by the inference engine to draw conclusions
• Follows a series of ‘IF Statements’

IGCSE COMPUTER SCIENCE

215

2023

Setting up an expert system

1. Information needs to be gathered from expert sources
2. Populate the created knowledge base
3. Create a rules base
4. Inference engine needs to be set up
5. Develop user interface
6. Testing

IGCSE COMPUTER SCIENCE

216

2023

Summary:

presentation title

217

20XX

Machine Learning

• This is the science of training computers with sample data so that they can go on to make predictions about new, unseen data, without the need to specifically program them for the new data
• Machine learning is when a program has the ability to automatically adapt its own processes and/or data

IGCSE COMPUTER SCIENCE

218

2023

Machine Learning…

• The system can make predictions or take decisions based on past experiences
• Can offer fast and accurate outcomes due to very powerful processing capability
• Can manage and analyse considerable volumes of data

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IGCSE COMPUTER SCIENCE

219

2023

Example: Search Engines

IGCSE COMPUTER SCIENCE

220

2023

Summary:

presentation title

221

20XX