IGCSE COMPUTER SCIENCE (ALL)

Computing technology

An all-encompassing term referring to the hardware, software and infrastructure that underpin current and emerging computer systems

e-waste

any form of discarded electronic equipment, including computing technology

2 processes in manufacturing that affect the environment

Raw material extraction: Sand for making screens, oil used to make plastics, e.t.c
Production: Fuel used in manufacturing, a lot of water used for semiconductor chips

How does usage affect the environment

Energy used to power devices
Cloud computing and data centers

Carbon footprint

the amount of carbon dioxide an individual or organization produces as a result of the energy they consume

How does disposal affect the environment

E-waste contains dangerous materials which can leak toxic substances into the ground and water supply, infiltrating the food chain and polluting the air (toxic fumes).

Use of computing technology to preserve the environment

Climate change information
Early warning to natural disasters
Conservation of wildlife using technology to collect data
Analysis of energy usage (allowing for optimization)

ethics

a set of moral principles that govern a person’s behaviour

privacy

the right to be left alone and free from unwanted scrutiny and intrusion

personal data

information that is person and unique to an individual

identity theft

the stealing of another person’s personal details, such as their bank account number, sort code or passport number, for the purpose of making purchases and running up debts in their name

List the privacy concerns of computing technology

Big data, Surveillance, Location-based services, privacy-enhancing tools

What is big data? (privacy concern)

Data analysts are able to learn more and more about us and gain insights about our behaviour by using huge volumes of personal data gathered from various sources.
(can benefit or harm society: prevent use of drugs or increase social engineering)

What is surveillance? (privacy concern)

Survelliance tehcnology always track us outside to prevent us from harm but this data can be used by criminals for harmful purposes

surveillance technology

CCTV, drones, number plate recognition, bugging and tracking devices used to monitor and record people’s acitivities, often without their knowledge

whistle-blower

someone who draws attention to the activities of an organization or person believed to be acting illegally or unethically

location-based services

services that enable people to access and share real-time location information online

What are privacy enhancing tools? (privacy)

Tools that help us stay secure while using computing devices such as encryption, cookie cleaners, anti-spyware, ad blockers, identity management service, password manager

digital inclusion

ensuring that everyone has affordable access to computing technology and the necessary skills to take advantage of it

digital divide

the gap between people who are technology-empowered and those who are technology-excluded

Impacts of digital exclusion (6 points)

Information and services, employment, democracy, economic growth, saving money, social isolation

Actions towards digital inclusion

Subsidies, encourage use of technology by changing government actions, training programs. building technology infrastructure

Professionalism in the context of computer science

Computer scientists must respect the wellbeing, privacy, and security of the environment and people, never stop learning and gaining skills and professional knowledge.

Intellectual property

a creation of the human mind that is unique and has commerical value

patent

an exclusive right granted to an inventor to make, use and sell an invention for a fixed period of time

What do licenses specify?

How many copies of the software you are allowed to use
Whether you can install the software on multiple devices
What type of organization can use the software
How long the software can be used for

Creative Commons

an organization that allows people to set copyright terms for their intellectual property. One use of a Creative Commons license is to allow people to copy material as long as it is not used commercially

Open-source software

software that is free to edit and redistribute

Proprietary software

software that belongs to an individual or a company. Its license specifies that users are not allowed to modify the source code and places restrictions on its use

Advantages of open source software

Free to use, can be modified, can be used to demonstrate programming concepts

Disadvatages of open source software

Might not be particularly user friendly and might look unprofessional
There might be little or no technical support available
Criminals may be able to identify and exploit vulnerabilities in code

What is AI?

The ability of a digital computer or computer-controlled robot to peroform tasks commonly associated with intelligent beings. Intelligent beigns are those that can adapt to changing circumstances.

Uses of AI in medicine

Digital consultations (using patient history to make diagnosis), Analysing test results, health monitoring

Uses of AI in everyday life

Personalized advertising, Virtual assistants, Flying an aircraft, Monitoring transactions to alert suspicious activity

DNA computing

Using the components of DNA such as adenine, thymine, guanine, and cytosine to store data; where codons store 3 digits.

Advantages of DNA computing over normal silicon-based ones

Always supply of DNA as long as there are cellular organisms
Large supply of DNA makes it a cheap resource
Can be made cleanly unlike toxic materials used to make traditional microprocessors
Much smaller than today’s computers

Nanotechnology

the manipulation of matter with a size of from 1 to 100 nanometers

nanometer

one millionth of a meter

Uses of nanotechnology

Self cleaning class (using nanoparticles)
Clothing (protection from UV light)
Scratch-resistant coatings
Medicine (ensures anti-cancer drugs that could harm normal tissue only reach the tumor)

Quantum computing

Use of quantum mechanics to crunch numbers much faster than traditional computers can. (because of superposition)

Quantum mechanics

a theory that explains the nature and behaviour of matter and energy on the atomic and subatomic level

subatomic particle

a unit of matter below the size of an atom, including elementary particles such as quarks that all atoms are made up of

superposition

the ability of a quantum system to be in multiple states at the same time until it is measured

qubit

a quantum bit, the counterpart in quantum computing to the binary digit or bit of classical computing

superconducting circuits

electrical circuits that have zero resistance, required to generate qubits

entanglement

co-dependence of the quantum states of pairs or groups of particles

network

an arrangement of computers and other devices connected together to share resources and data

network service

an app running on a server which provides facilities or operations such as data storage, printing or communications

LAN

a network that covers a relatively small geographical area, often a single site

WLAN

a local area network in which connected devices use high-frequency radio waves to communicate

PAN

network used for data transmission over short distances by computer devices, such as laptops, mobile phones, tablets, media players, speakers and printers

Bluetooth

a protocol for the short-range wireless interconnection of electronic devices

WAN

a network that covers a large geographical area. It connects together two or more LANs and is usually under shared ownership

largest WAN / mesh network

the Internet

client-to-server network

a network that has atleast one server to provide services to the client computers

3 step process of a client accessing files from the sever

1) A client makes a connection using its address.
2) The client makes a service request to the server.
3) If the request is valid, the server sends the requested data to the client using the address.

peer-to-peer network

a network that doesn’t have any dedicated servers. Each computer in the network can act as client and server

network topology

describes how devices on a network are connected together

Advantages of networks (3 points)

Devices can share resources, Files can be accessed through any computer in the network, Data is easy to backup as it is stored centrally in the server

Disadvantages of networks (3 points)

Purchasing network hardware is expensive, managing large networks are complicated, viruses may infiltrate the network and infect every computer

Network Interface Card (NIC)

A small piece of hardware in a device that provides the capability to connect to wireless networks.

Wireless Acess Point (WAP)

a device that is used to connect one or more computers wirelessly to an existing physical wired network

Router

Connect one network to another such as your home’s LAN to the Internet.

Switch

Connect wired devices to a network and know the MAC address of each computer and route data to each computer specifically.

Hub

Connect wired devices to a network but send all the data to all the computers whether they want it or not.

Bridge

Connect LANs together to create a WAN

Bus Topology

Each node is connected to a single cable, and data can be sent in both directions. Terminators are placed at the end of each side of the cable to absorb signals that have reached the end. Data is sent to all nodes but is only accepted by the node that requires it.

Advantages of Bus Topology (2 points)

1. Relatively cheap to install since only one cable is needed

2. Easy to add extra nodes

Disadvantages of Bus Topology (4 points)

1. Whole network fails if cable is damaged

2. difficult to identify fault on cable

3. More nodes cause network to operate slower because more collisions happen

4. All data sent is received by all devices so there is a security risk

Ring Topology

Each node is connected in a closed loop in the shape of a ring. The data continues along the ring in the same direction until it reaches its destination.

Advantages of Ring Topology (2 points)

1. Adding extra devices does not affect performance

2. easy to add network devices

Disadvantages of ring topology (4 points)

1. Whole network fails if a cable is damaged or a device fails

2. Removing or adding device shuts down network temporarily

3. Difficult to identify fault on network

4. More expensive to install than bus topology since more cable is used

Star Topology

Has one central point with all other nodes connected to it, which is either a hub or a switch which directs and receives messages to the correct recipients.

Advantages of star topology (4 points)

1. Damaged cable does not stop entire network from working

2. If switch is used only required nodes receive message

3. Easy to locate faults because usually one device is involved

4. New device can be added or removed without closing the network

Disadvantages of star topology (2 points)

1. If the hub or switch fails the whole network will fail

2. Expensive to install because of the amount of cable needed and the hub/switch

Mesh Topology

Each node is connected to atleast one other node, and it is more common for them to be connected to more than one node. The most efficient route is typically calculated before data is sent thorugh it.

Adantages of mesh network (3 points)

1. Very fault tolerant - If one device fails messages can be rerouted around it

2. Very high performance because each device is likely connected to multiple other devices

3. In a wireless mesh network each node extends the range of the network

Disadvantages of mesh networks (2 points)

1. Difficult and expensive to install wired mesh networks

   1. Diffiuclt to manage due to the number of connections within the network

Internet

a worldwide system of interconnected networks that enables information to be exchange and shared

communication media

the means by which data is transmitted between devices on a network (optic fibre, microwaves, e.t.c.)

range

How far data can be sent

protocol

a set of rules that govern how communications on a network should be formatted and what data they should include

eavesdrop

having unauthorized sight of data being sent from one computer to another over a network

Advantages of wired connectivity (3 points)

Faster (less latency, higher bandwith, larger range), Not easy to intercept or eavesdrop, less susceptible to interference

Disadvantages of wired connectivity (2 points)

Expensive to install and reconfigure, requires many cables

Advantages of wireless connectivity (5 points)

No need for cable to connect devices (less hardware, easy to connect), allows users to use their own device, wider range of devices can communicate because it does not depend on having the right cable, cheaper

Disadvantages of wireless connectivity ( 4 points )

Slower data transmission speeds, Interference from other wireless devices, Walls or physical objects can affect performance, Data must be encrypted to prevent eavesdropping or interception

latency

the delay encountered by data travelling through a network

SMTP Protocol (Simple Mail Transfer Protocol)

Used when sending emails through the internet from client to server and then server to server until it reaches its destination

POP3 Protocol

Used by clients to retrieve emails from a mail server (all emails are downloaded when there is a connection between the client and server)

IMAP

Messages can be read and stored on the message server so messages can be read from multiple devices rather than being downloaded into one

Ethernet

A family of protocols used in wired LANs

Wi-Fi

Protocol that sets out how data is transmitted on wireless LANs

TCP (Transmission Control Protocol)

Breaks up messages sent over the internet into small chunks called packets and reassembles the packets at the other end, using checksums to detect errors.

checksums

A technique that involves applying a mathematical formula to transmit a resulting number value with transmitted data, and then this formula is applied again in the receiving end to check for errors. If it does not match, the computer requests the data again

IP (Internet Protocol)

Routes individual packets from one IP address to another utilizing the router

Order of the TCP/IP protocol stack

Application, Transport, Internet, Link

Application layer

Interacts with user to provide access to services and data sent or received in a network

Transport layer

Manages end-to-end communication over a network

Internet layer

Deals with sending data across multiple networks from the source to the destination network