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Learn about data structures including arrays, records, lists, tuples, linked-lists, graphs, stacks, queues, trees, binary search trees and hash tables. Based on the OCR H446 Computer Science A-Level specification. Exam Board: OCR A-Level 4.2 - Data Structures Specification: Computer Science H446 Watch on YouTube : Arrays Records Lists & tuples Stacks Queues Linked lists Trees Graphs Hash tables Data structures are used to organise and store data so it can be accessed and processed efficiently , often through the use of an index or reference . They can be static , meaning their size is fixed during program execution , or dynamic , allowing them to grow or shrink as data changes . Arrays An array is a data structure that stores a collection of items of the same data type , with each item accessed using an index . A one-dimensional (1D ) array is a simple sequence of values , such as test scores for a single person : scores = [12, 15, 18, 20] . A two-dimensional (2D ) array is like a table or grid , made up of rows and columns - for example, storing a timetable or test scores for a class . A three-dimensional (3D ) array stores data in multiple layers , like a series of 2D grids . For example, test scores for a class across multiple subjects . This page is under active development. Check here for the latest progress update. YouTube video uploading soon Records A record groups together related but different types of data under one name . Each individual piece of data within a record is called a field and each field can have a different data type (e.g. string , integer , Boolean ). For example, a student record might include fields such as Name (string ), Age (integer ) and Enrolled (Boolean ). Records are often used in databases or programming to represent real-world entities where multiple attributes need to be stored together . YouTube video uploading soon Lists & Tuples A list stores an ordered collection of items , which can be changed (mutable ) after creation. Items in a list can be added , removed or modified , and they can be of different data types . For example, in Python : myList = [10, "apple", True] . A tuple is similar to a list but is immutable , meaning its contents cannot be changed once created . Tuples are often used for fixed sets of data that should not be altered , such as coordinates or dates . For example: myTuple = (3, 5, 7) . YouTube video uploading soon Stacks A stack stores data in a last in , first out (LIFO ) order, meaning the most recently added item is the first one to be removed . It works much like a stack of plates - you can only add or remove from the top . Two integral functions are push and pop . The push operation adds (or “pushes”) a new item onto the top of the stack . The pop operation removes (or “pops”) the item from the top of the stack . Stacks are commonly used in undo features , function calls and expression evaluation , where tracking the most recent item first is important . YouTube video uploading soon Queues A queue stores items in a first in , first out (FIFO ) order, meaning the first item added is the first one removed . New items are added at the rear of the queue using an enqueue operation, and items are removed from the front using a dequeue operation. Queues are often used in task scheduling , print spooling and data buffering , where operations must occur in the same order they were requested . YouTube video uploading soon Linked Lists A linked list is a dynamic data structure made up of a series of elements called nodes , where each node contains data and a pointer to the next node in the sequence . Unlike arrays, linked lists do not store elements in contiguous memory locations , making it easy to insert or delete items without having to shift other elements . The head is the first node in the list , and the last node usually points to null , indicating the end of the list . YouTube video uploading soon Trees A tree is a hierarchical data structure made up of nodes connected by branches , starting from a single root node . Each node can have child nodes , and nodes without children are called leaf nodes . Trees are useful for representing data with natural hierarchies , such as file systems or organisational charts . A binary search tree is a special type of tree where each node has at most two children - a left and a right . All values in the left subtree are smaller than the parent node , and all values in the right subtree are larger . This structure allows for efficient searching , insertion and deletion of data , often much faster than in lists or arrays . YouTube video uploading soon Graphs A graph is made up of nodes (also called vertices ) connected by edges and is used to represent relationships between items. Graphs can be directed , where edges have a specific (one-way) direction , or undirected , where connections go both ways . They can also be weighted , where edges have values such as distance or cost , or unweighted , where all connections are equal . Graphs are widely used in computing, for example, in social networks (users and friendships ), maps (locations and routes ) and network routing algorithms . YouTube video uploading soon Hash Tables A hash table stores key–value pairs and allows for very fast data access . It uses a hash function to convert a key (such as a name or ID ) into an index (hash value ), which determines where the associated data (value ) is stored in memory . When retrieving data , the same hash function is applied to the key to find the value’s location instantly , making lookups close to constant time complexity on average . If two keys produce the same hash (a collision ), techniques such as chaining or linear probing are used to handle it . Hash tables are commonly used in databases , caches and programming languages for tasks like fast searching and indexing . YouTube video uploading soon Q uesto's K ey T erms Arrays: array, 1-dimensional, 2-dimensional, 3-dimensional, static Records: record, field, data type, primary key Lists and Tuples: list, tuple, mutable, immutable, dynamic Stacks and Queues: stack, queue, last in first out (LIFO), first in first out (FIFO), push, pop, enqueue, dequeue, pointer Linked Lists: linked list, null Trees & Graphs: tree, binary tree, binary search tree, root node, branch, graph, weights, directions Hash Table: hash table, key, value, collision, linear probing, chaining D id Y ou K now? Trees are used for dialogue options in narrative video games , displaying possible paths based on the player’s previous choices . The final ' suicide mission ' of Mass Effect 2 has hundreds of possible variations depending on ship upgrades , squad member loyalty , and assigned roles during the last mission . 4.1 - Data Types A-Level Topics 4.3 - Boolean Algebra

Learn about the advantages and disadvantages of networks, the five types of network - LAN, WAN, PAN, MAN and VPN - and differences between wired and wireless networks. Based on the 2020 Eduqas (WJEC) GCSE specification. 3.1: Network Characteristics Exam Board: Eduqas Specification: 2020 What is a network? A network is more than one computer system connected together allowing for communication and sharing of resources . There are many benefits but also some drawbacks to using a network compared to having an unconnected ('standalone' ) computer: Advantages of Networks Easily share files , software and hardware between computers. Disadvantages of Networks There is an initial cost because network devices like routers are required . Larger companies will need to buy and maintain a server . Log in from any connected computer and access your data and files. A network manager / administrator might need to be employed to maintain the network . An administrator can monitor network activity and control security settings. Data from computers on the network can be automatically backed up on central storage. Security breaches are more likely and malware , such as worms, can spread quickly across the network. If the web server fails , all connected computers won't be able to access files or log on . Network Types Networks can be split into different types , usually categorised by their geographical distance apart and the area that they serve. Local Area Network A local area network (LAN ) has computer systems situated geographically close together , usually within the same building or small site , like a school or office . Wide Area Network A wide area network (WAN ) has computer systems situated geographically distant to each other, possibly across a country or even across the world . The internet is an example of a WAN that spans the globe. Personal Area Network A PAN is a personal network for an individual , such as a photographer connecting a smartphone, desktop computer and printer together. Metropolitan Area Network A MAN is larger than a LAN but smaller than a WAN and typically covers a relatively large area like a university campus, town or city . Virtual Private Network A VPN allows for a secure and encrypted connection to a public network like the internet. It is often used to protect an individual's privacy by concealing their real location. Wired & Wireless Networks Wired Connections Wireless Connections Wireless connections, such as WiFi or Bluetooth , use no cables but require a wireless network interface card (WNIC ). Wireless connections generally have a slower speed and can be affected by the computer's distance from the wireless router as well as obstacles like walls or bad weather. Wired connections use physical cables , such as copper or fibre optic wires , and require a network interface card (NIC ) to connect to a network. These wired connections use a wired connection protocol - most commonly Ethernet . Restricted Movement Faster More Secure NIC Required Freedom of Movement Slower Less Secure WNIC Required Q uesto's Q uestions 3.1 - Network Characteristics: 1. A retirement home for the elderly is considering installing a LAN , give 3 benefits and 3 drawbacks they might find of using a network . [6 ] 2a. Describe the difference between a LAN and WAN . [2 ] 2b. Give an example of how a LAN and a WAN could each be used . [ 2 ] 3 . Explain the differences between a PAN , MAN and VPN . [ 3 ] 4. For each of the scenarios below, state which network type would be most suitable : a. The IT rooms of a secondary school . [ 1 ] b. A study in a house with a desktop and printer. [ 1 ] c. Using online banking when abroad on a holiday to stay secure . [ 1 ] d. A large technology company with offices across Europe . [ 1 ] e. Council offices with several locations across Manchester . [ 1 ] 5. Briefly compare wired and wireless networks . [ 8 ] 2.2 - Boolean Algebra 3.2 - Data Packets & Switching Theory Topics

Learn about the purpose of Green IT, the benefits for an organisation following its practice and methods of use. Based on the 2016 OCR Cambridge Technicals Level 3 IT specification for Unit 2 (Global Information). 4.3 - Green IT Exam Board: OCR Specification: 2016 - Unit 2 What is 'Green IT'? ‘Green IT ’ is to use computers and IT resources in an efficient and environmentally responsible way to reduce an organisation’s carbon footprint . To 'reduce carbon footprint ' means to decrease the amount of pollution (such as CO2 ) produced by an organisation and to engage in more eco-friendly practice. Examples of Green IT Practice Global Requirements of Green IT United Nations Climate Change conferences occur every year and are attended by leaders of each country in the United Nations. The conferences establish obligations for countries to work towards reducing their carbon footprints and emissions of greenhouse gases . Whilst Green IT is not specifically mentioned in these talks, IT is a hugely important sector with large annual emissions that need to be reduced to meet the climate change limitations, such as the Paris Agreement. In the UK, the Greening Government ICT Strategy (running between 2011 and 2015) was an annual report that investigated how IT use could become 'greener' within the government . Positive consequences of this strategy included: Using more cloud storage technology , enabling fewer individual storage devices to be purchased, reducing emissions . Using social media more widely to contact voters - saving money by posting fewer letters and leaflets. Increasing the use of teleconferencing and video calls - reducing the need for unnecessary travel to meetings and avoiding the generation of heavy pollution. Q uesto's Q uestions 4.3 - Green IT: 1. What is meant by the term 'Green IT '. [3 ] 2a. Explain four ways that an organisation can follow good green IT practice . [4 ] 2b. Describe two reasons why it is beneficial to a company of following Green IT . [4 ] 3a. Why are the United Nations Climate Change conferences important ? [2 ] 3b. Describe two ways that the UK government have used Green IT . [4 ] Turn off computers , monitors and other connected devices when not in use . Adjust power options to help minimise power consumption. Use cloud storage or virtualisation to reduce the number of physical devices being bought, powered and maintained. Repair older devices rather than throwing them away. Consider if it is necessary to print a document before doing so and print only what is required . Recycle ink cartridges and paper . Donate older equipment to charities or schools for reuse . Why use Green IT? It is in an organisation's best interests to use Green IT practices for the following reasons: To become more sustainable by reducing the company's carbon footprint and positively impacting the environment . Reducing energy costs (e.g. by turning equipment off when not in use) and saving money . Improving the public image of the organisation as people are increasingly environmentally conscious and will prefer to do business with a company that follows environmentally-friendly policies. 4.2 - Global Legislation Topic List 5.1 - Data Types & Sources

Learn about crucial laws in place to protect data and privacy, including the Data Protection Act (2018), Computer Misuse Act (1990), RIPA (2000) and the Freedom of Information Act (2000). Based on the 2016 OCR Cambridge Technicals Level 3 IT specification for Unit 2 (Global Information). 4.1 - UK Legislation Specification: 2016 - Unit 2 Exam Board: OCR There are many types of legislation - laws that have been written into use - that concern data storage, protection and the use of information. In an exam, the year the law was introduced must be stated . In 2018 the European Union introduced GDPR (General Data Protection Regulation ) to protect the privacy of data for people in the EU. The UK matched this by updating the Data Protection Act introduced in 1998 to become the Data Protection Act (2018) . This act protects the data of individuals that is stored on computers and processed by organisations. How the Data Protection Act works: Each person who has their data stored is known as a data subject . An employee within an organisation must be appointed as a data controller and it is they who are responsible for registering with the Information Commissioner . The Information Commissioner is the person in the UK who is responsible for managing several laws , most significantly the Data Protection Act. When registering with the Information Commissioner, the organisation's data controller must be clear on exactly: What information they are collecting, Why it is being collected, What the data will be used for . The six principles of the Data Protection Act (2018) state: 1. Data must be collected lawfully and processed fairly. 2. Collected data must only be used for the reasons specified. 3. Data must be relevant and not excessive. 4. Data must be accurate and up-to-date. 5. Data must not be stored for longer than necessary, 6. Data must be stored and processed securely. Actions organisations must take to stick to the Data Protection Act (2018): The company must appoint and register a member of staff to act as the organisation's data controller . The data controller is responsible for communicating with the Information Commissioner and ensuring the principles of the DPA are not broken . There must be strong security measures in practice to protect data from being accessed or transferred without authorisation . This could be in the form of physical or digital protection methods enforced by the company. Staff should be trained so that they are clearly aware of their responsibilities and each principle is adhered to. For example, they should know that data can only be used for the reasons specified when it is collected and should not be passed to others without the permission of the data subject. Data subjects should be given the opportunity to alter their data and make changes if it is incorrect . Data should be deleted when it is no longer needed , so organisations should periodically assess both the accuracy and relevance of storing each data subject's information. Data subjects have the right to make a Subject Access Request (SAR ) and receive a copy of the data which is stored about them. Companies must abide by this request by verifying the user's identify and presenting the data to them securely . Rights of data subjects: Under the Data Protection Act, individuals have a right of access to any information that is stored about them by public bodies . If an individual wishes to access their data they must submit a Subject Access Request (SAR ) which results in the following steps: The organisation's data controller must be written to and told exactly what information is required to access. An administrative fee should be paid to the organisation (but only if the request requires excessive efforts to fulfil ). The organisation must provide the requested information within 40 days . The individual must verify their identity using appropriate ID because only the data subject can request their data . Computer Misuse Act (1990) This act was introduced as computers became cheaper and more common at home and work . The act attempts to stop and punish those who use computers inappropriately . Breaking any of the three principles could result in fines and a jail sentence but only if it can be proved it was done on purpose and not by accident. The Computer Misuse Act (1990 ) includes three main principles : 1. No unauthorised access to data. Example: Hacking a computer system. 2. No unauthorised access to data that could be used for further illegal activities. Example: Accessing personal data to use as blackmail or identity theft. 3. No unauthorised modification of data. Example: Spreading a virus to change data. Data Protection Act (2018) / GDPR Freedom of Information Act (2000) This act allows people to request public authorities to release information . Public authorities include local councils , government departments , universities and hospitals . A freedom of information request must be formally submitted in a letter or email and a reply from the organisation is required within twenty days of receiving the request. A simple freedom of information request might be the average response times of the local ambulance service in the past year. Certain requests will not be accepted , such as if processing the request would be too expensive or if it involves sensitive information protected by the Data Protection Act (2018 ). Regulation of Investigatory Powers Act (2000) This act (often shortened to RIPA ) was introduced in response to the increase in both criminal and terrorist activities on the internet, it is used to monitor and access online communication of suspected criminals . If criminal activity is suspected by an individual then this act grants the following powers : Internet Service Providers (ISPs) must provide access to the suspect's online communication , such as emails or social media. Locked or encrypted data may be accessed such as online messages. ISPs could install surveillance equipment or software to track the suspect's online activity . Surveillance may take place to physically track the suspect , e.g. in private vans or by undercover officers in public spaces. Access must be granted to personal information . This act became controversial as its use widened and local councils were using it for minor offences - a Scottish council used the act to monitor dog barking and a council in Cumbria gathered video evidence about who was feeding pigeons . The act has since been changed to only allow the surveillance of crime suspects . Copyright, Designs & Patents Act (1988) This act makes it a criminal offence to copy work that is not your own without the permission of the creator or the copyright holder. This can refer to text, images, music, videos or software. Owning the copyright of an image might not prevent others from copying and using it but this act means that the owner can bring legal proceedings in court to those who have stolen their work . Creators of copyrighted work can take ownership of their work and control how it is used . Others must ask for permission to use the work otherwise the copyright holder can ask for it to be removed or demand a fee for its use . This act specifically prohibits the following actions: Making copies of copyrighted material to sell to others . Importing and downloading illegally copied material (except for personal use). Distributing enough copyrighted material to have a noticeable effect on the copyright holder . Possessing equipment used to copy copyrighted material , as part of a business. Information Commissioner's Office (ICO) Codes of Practice Protection of Freedoms Act (2012) There are seven sections to this act, revolving around the protection of personal data . It was introduced because there was little legislation about biometric data , and to update older laws . IT-related sections are summarised below: Part 1 - States how biometric data (e.g. fingerprints and DNA) is stored, handled and collected. For example, parents must give consent before their child gives biometric data to a school. Also, biometric data for suspects of minor offences is deleted after the case is closed. Part 2 - Creates new regulation for CCTV and ANPR (automatic number plate recognition) use. Part 5 - The Disclosure & Barring Service (DBS) was created to run background checks on anyone wanting to work with children or vulnerable people. Part 6 - Extends the Freedom of Information Act (2000) allowing for wider requests to be made . The information commissioner is the senior government official in charge of the country's freedom of information requests and the protection of personal data . The Information Commissioner's Office describes itself as "The UK’s independent authority set up to uphold information rights in the public interest, promoting openness by public bodies and data privacy for individuals". The ICO publishes codes of practices about various data protection and privacy topics , usually related to explaining the Data Protection Act . For example, the ICO has a code of practice regarding how organisations should share data and another code of practice about the use of CCTV . The ICO offers help and support to both individuals (such as giving access to students to their exam results) and organisations (such as support with legal electronic marketing). Privacy and Electronic Communications Regulations (2003) This law (which was updated in 2011 ) regulates how organisations can communicate with individuals . Companies must stick to the following rules: It is an offence to directly contact an individual unless they have specifically opted-in to receive communication. This is commonly managed by using tick boxes on online stores where you must opt-in to receiving promotional material. Companies must clearly state who they are when contacting customers, such as displaying the phone number when calling - and not 'hiding' the number. Organisations must explain how cookies are used on their website . Companies must only contact customers through communication channels that the customer has previously permitted . This can be done with tick boxes when signing up. Customers can select or de-select methods such as email , phone calls and text messages . The Information Commissioner's Office (ICO) is responsible for this regulation and can fine companies that commit unsolicited communication up to £500,000. It is the customer who benefits and is protected by this regulation. Equality Act (2010) The government states that "The Equality Act legally protects people from discrimination in the workplace and in wider society." Discrimination because of protected characteristics such as gender , race , religion , age and disability are specifically punishable by legal action. The aim of the act is to end discrimination in the workplace and open up fair opportunities for every employee regardless of behavioural or physical characteristics that are outside of their control . Within a company, the Equality Act protects staff by stating protected characteristics should not be a factor in an employee's promotion or change of role. Information must be presented in a format accessible to all staff . Q uesto's Q uestions 4.1 - UK Legislation: 1. Create a flashcard or PowerPoint slide for each legislation above. Explain the purpose of the legislation , its main principles and whom it affects . [5 each ] 3.6 - Information Systems Topic List 4.2 - Global Legislation

Learn about network topologies including client-server, peer-to-peer, bus, mesh and star. Based on the 2016 OCR Cambridge Technicals Level 3 IT specification. 3.3 - Network Characteristics Exam Board: OCR Specification: 2016 - Unit 1 Network Topologies Network topology refers to the arrangement of computer systems on a network . Devices in a network topology diagram are often called ' nodes ' . Client-Server Network Clients make requests to a server , the server manages that request and responds . For example, if the user (client) makes a request to access www.csnewbs.com to a web server . Large services like Amazon and Google will need very powerful servers to handle millions of requests a second. The client is completely dependent on the server to provide and manage the information. The server controls network security , backups and can be upgraded to manage higher demand. Disadvantages: Large amounts of traffic congestion will cause the network to slow down . If a fault occurs with the server then the whole network will fail . IT technicians may be required to manage and maintain the network . Malware , such as viruses, can spread quickly across the network. Peer-to-Peer Network For peer-to-peer networks , data is shared directly between systems without requiring a central server . Each computer is equally responsible for providing data. Peer-to-peer is optimal for sharing files that can then be downloaded. Bus Topology The nodes are connected to a bus (a central cable which transfers all data on the network). How it works: The bus transfers data packets along the cable . As the data packets arrive at each computer system, the computer checks the destination address contained in the packet to see if it matches its own address . If the address does not match , the computer system passes the data packet to the next system . If the address of the computer system matches the destination address in the data packet, it is accepted and processed. At both ends of the cable are terminators to mark the end of the bus. Advantages: Because of the simple layout, it is easy to attach another system to the main cable without disrupting the whole network . A bus topology is quick to set up once the main cable has been established making it optimal for temporary networks . A bus topology is cost-effective because it usually contains less cabling than other topologies and requires no additional hardware (like a hub or switch). Disadvantages: Poor security as data packets are passed on to each system on the network. Data collisions are likely - this is when two systems attempt to transfer data on the same line at the exact same time. Resending the data wastes time and slows down the network . The main cable will only have a limited length which can become crowded and slows network speed as more systems are attached. The main cable must also be terminated properly . Token Ring Topology In a token ring network , computer systems are connected in a ring or a loop. How it works: A token (small data packet) is sent around the ring in one direction, being passed from one computer system to the next. A computer seizes the token and includes its own data when it transfers data. As the token arrives at each computer system, the system checks the destination address contained in the packet to see if it matches its own. If the addresses match, the computer processes the data otherwise it ignores it. Advantages: Data collisions are avoided as data packets are transmitted in one direction around the ring. Attaching more systems to a ring topology won't affect the transfer speed as much as other layouts like a bus topology because the data is transferred at a consistent speed . Disadvantages: If any system on the network fails then the whole network fails as the loop is broken and data can't be transferred to all systems. To add a new system to a ring topology the network must be temporarily shut down . Star Topology In a star network , each computer system is connected to a central node: a hub or switch . How it works: Each node is connected to the central node (usually a hub or switch ) and transfers its data packets here. The hub/switch looks at the destination address and transfers the packets to the intended computer only. Advantages: A star topology has improved security because data packets are sent directly to and from the hub / switch in the centre and not necessarily all devices like in a bus or ring topology. New systems can be attached directly to the central system so the network doesn't need to be shut down . System failures of attached computers won't usually cause complete network failure. Transfer speeds are generally fast in a star topology as there are minimal network collisions . Disadvantages: Extra hardware (the hub or switch) is required to be purchased, installed and maintained. If the central system (the hub or switch) fails then the whole network will be unusable until the error is fixed. Mesh Topology In a mesh network, each computer system is connected to every other computer system . How it works: Data packets are transferred to the destination address along the quickest path, travelling from node to node. If a pathway is broken, there are many alternative paths that the packets can take. Advantages: If one cable or system fails then data packets can take an alternative route and still reach the destination address. Because of the large possible number of systems and connections, a mesh topology can usually withstand large amounts of data traffic . New systems can be added to the network without disrupting the entire topology . Disadvantages: Because of the possibly large amount of cables required (especially in a complete mesh topology) this network layout can be expensive to install and maintain . Redundant cabling should be avoided - this is when cables are connected between systems that won't ever need to communicate . Configuration Before a computer system can use a network, three pieces of information must be configured (set up) correctly. IP Address An IP address is used to uniquely identify computer systems on a network , allowing communication between them. An example of an IP address is 195.10.213.120. Default Gateway When data is to be sent from one network to another , it must be sent through a default gateway . This default gateway is usually a router that connects the local network to another network . On many home networks , the default gateway will use the same private IP address : 192.168.1.1 Network managers can use automatic configuration which is quicker and easier to set up . A new device can connect to and use a network automatically , such as free WiFi in an airport. Network managers can also set manual configuration which improves security as new devices can’t be used until the addresses have been configured by a technician . This stops unauthorised devices from connecting to the network. Subnet Mask Subnetting is the act of dividing a physical network into smaller 'sub' networks (known as subnets ) . This helps to reduce traffic and means that users can externally access parts of a network (e.g. emails from home) without having to open the entire network. A subnet mask is used to define these subnets . The mask is used to determine the start and end address of each IP address in a subnet. A common subnet mask is 255.255.255.0 as making the first 3 sections full restricts the fourth section to 256 unique values. For example 113.12.14.230 and 113.12.14.157 are in the same subnet but 114.12.14.127 wouldn't be. Q uesto's Q uestions 3.3 - Network Characteristics: 1 a. Describe how peer-to-peer networks and client-server networks function. 1b. Give one use for both types of network. 2a. Draw and label a diagram for all 6 network topologies . 2b. Describe 2 advantages and 2 disadvantages of each network topology . 3 . What is an IP address ? Why is it necessary for networks? 4. Describe what is meant by a default gateway . 5a. What is subnetting ? 5b. What is the purpose of a subnet mask ? 5c. State a common subnet mask . How many unique devices can be used on a network with this subnet mask? 6. Describe 1 reason why a network manager may use automatic configuration and 1 reason why they may use manual configuration . Advantages: The network can be controlled centrally from the server to easily backup data and update software . Hardware, software and resources can be shared across the network, such as printers, applications and data files . The network allows for improved scalability , meaning more clients can be easily added to the central server . Disadvantages: Without a dedicated server there is no central device to manage security or backups . Backups must be performed on each individual system. Computer performance will decrease with more devices connected to the network, especially if other machines are slow. Advantages: This is a simpler network than client-server to set up as no server is required . Clients are not dependent on a server . Perfect for quickly sharing files between systems , such as downloading media files. 3.2 - Virtualisation Topic List 3.4 - Connection Methods

Test your ability to create a more complex program in Python based on a given scenario. Perfect for students learning GCSE Computer Science in UK schools. Extended Task 3 Hi, Susanna here, I want to make a blackjack-like program that I can play for fun at home in between revising for Computer Science. The aim of my blackjack game is to get as close to 21 as possible with the most number of cards, without going over. So... The user can choose whether to be hit with a new card (a number between 1 and 8) or fold and stop. Each number they are dealt adds up to their total . If the total goes over 21, then they lose . If they bust (when over 21) or folded then their final number and their number of cards is displayed . Blackjack For this task, you will need to create a document and include the following sections (with screenshots where appropriate): An introduction to explain the Purpose of your program . A List of Requirements for a successful program. Screenshots of your code (with comments in your code to show understanding). Testing – Create a plan to show how you will test your program and then explanations of any errors that you found and how they were fixed . An Evaluation of what worked, what didn’t, and how you met each of your requirements from your original list. Also, discuss further improvements that you could have made to improve your program. Example solution: Helpful reminders for this task: Think about the type of loop that you need. Will you need more than one loop? What variables will you need? Remember to use an input . What will you ask the user? How will you use their response? Remember to use ‘import random’ and randint to create a random number . What outputs do you need and when? What should you display… After each hand? At the beginning? At the end? ⬅ Extended Task 2 (Lottery) Extended Task 4 (Vet Surgery) ➡

Learn how to use App Inventor 2 to create simple programs. Try to complete the final task (7) on this page. Perfect for Key Stage 3 students to experiment with block coding, objects and properties. App Inventor Task 7 - Pop-up Blob The previous apps have been preparing you to make a longer and more complicated app. Now we will put together all of the skills you have learned to create a fun game. Check the video: Open App Inventor 2 (use the button below) and create a new project. You will need to log in with a Google account. App Inventor 2 Ready for a challenge? This is what the program looks like in Designer layout. To the left are the components with all their Properties correct. To the right are the Components names. Put the three labels and button inside a HorizontalArrangement from the Layout section of Palette . The Text for ScoreLabel is 'Score: 0'. The Text for TimeRemainingLabel is 'Time Remaining:'. The Text for SecondsLabel is '20'. Place an ImageSprite inside a Canvas (both from the Drawing and Animation section of Palette ). Download the blob image from the Basics page here and upload it as the Picture for the ImageSprite . Change to Blocks layout and drag a initialize global to block from Variables . Type 'Score' in the empty space to create a variable that we will use to track how many times the blob has been touched. Attach a 0 block from Math to start the score at 0. This big block of code uses some of the concepts which you have used before. Whenever the Blob is touched the variable Score is increased by 1. The X and Y coordinates of the Blob are changed by random numbers so it will appear in a random location on the screen. The bottom blocks change the ScoreLabel to show the current score. Every second that the timer ticks we want to check if the score is more than 1 (to check it hasn't reached 0). If it is more than 1 second then the time will count down by 1. In the else part you need to add the following: Set Blob Enabled to false . Set Blob Visible both to false . Set TimeRemainingLabel Visible to false . Set SecondsLabel Visible to false . When the Reset Button is clicked the score variable is changed to 0 and the Seconds label is rewritten to 0. Make sure you use the " " block from Text and not a block from Math. Inside the when ResetButton Click block you need to reverse the code you have added for the else block when the timer ticks: Set Blob Enabled to true . Set Blob Visible both to true . Set TimeRemainingLabel Visible to true . Set SecondsLabel Visible to true . Extra Step: Challenges 1. Large score display . If you watch the video at the top of the page again, you will see that when the time runs out (is less than 1) some of the labels turn invisible and the TextColour and FontSize of the ScoreLabel changes. Try to do the same in your app. Remember to reverse what you have done in the code for the reset button; otherwise, the labels will still be invisible! 2. Customise your game . Change the background of the Canvas to an image, change the blob to a different image and add a sound when the character is 'popped'. 3. *HARDER Challenge* Add a High Score Label . Follow these hints carefully and use the colours to help you. You need to initialize a new Variable called HighScore and set it to 0 . You also need to add a new HighScoreLabel and put it in your Horizontal Arrangement in Designer layout. Add an if then block in the else part of the When Timer Timer block you already have. If Score > HighScore then HighScore = Score . This will change the value of HighScore to the current Score if it is higher than the current high score. Remember to make the HighScoreLabel display the new HighScore . KS3 Home

Learn about how images are represented in a computer system, including file size, resolution, colour depth and metadata. Based on the J277 OCR GCSE Computer Science specification (first taught from 2020 onwards). 2.4d: Image Storage Exam Board: OCR Specification: J277 Watch on YouTube : Pixels & Resolution Colour Depth & Metadata Image File Size Bitmap Images Bitmap images are made of pixels - single-colour squares - arranged on a grid . Each pixel is assigned a binary value which represents the colour of that pixel. The quality of a bitmap image depends on the total amount of pixels , this is known at the image resolution . Because it is made of pixels, scaling a bitmap image up will result in a visible loss of quality . Most images on computers are bitmaps, such as photos and screenshots . How to Calculate the File Size of a Bitmap File Size = Resolution x Colour Depth The resolution of an image is the width in pixels multiplied by the height in pixels. The colour depth (also known as bit depth ) is the number of bits that are used to represent each pixel's colour . 1 bit represents 2 colours (0 or 1 / black or white). 2 bits will allow for 4 colours, 3 bits for 8 colours, 4 for 16 etc. A colour depth of 1 byte (8 bits ) allows for 256 different colours . Remember you must multiply the colour depth , not the number of available colours (e.g. 8 not 256). The RGB (Red , Green , Blue ) colour model uses 3 bytes (a byte of 256 red shades , a byte of 256 green shades and a byte of 256 blue shades ) that together can represent 16.7 million different colours. Example Height = 6 bits Resolution = height x width Resolution = 8 x 6 = 48 bits -------------------------- Colour Depth = 1 bit (only 2 colours) -------------------------- File Size = Resolution x Colour Depth File Size = 48 x 1 = 48 bits File Size in bytes = 48 ÷ 8 = 6 bytes File Size in kilobytes = 6 ÷ 1000 = 0.00 6 kilobytes Width = 8 bits Look carefully at the exam question to see if the examiner is expecting the answer in bits, bytes or kilobytes . Always calculate the file size in bits first then: Divide the file size in bits by 8 to convert to bytes . Divide the file size in bytes by 1000 to convert to kilobytes . Metadata for Images Metadata is additional data about a file . Common image metadata includes: Height and w idth in pixels Colour depth Resolution Geolocation Date created Last edited File type Author details Metadata is important, For example, the dimensions must be known so the image can be displayed correctly . Metadata for a picture taken on a smartphone: width in pixels, e.g. 720 height in pixels, e.g. 480 Q uesto's Q uestions 2.4d - Image Storage: 1. Describe how bitmap images use pixels . [ 2 ] 2. Define the terms image resolution and colour depth . [2 ] 3. How many colours can be represented with a colour depth of... a. 1 bit [ 1 ] b . 5 bits [ 1 ] c. 1 byte [ 1 ] 4. How is the file size of an image calculated? [2 ] 5a. An image file has a width of 10 pixels , a height of 8 pixels and a colour depth of 2 . What is the file size in bytes ? [3 ] 5b. An image file has a width of 120 pixels , a height of 120 pixels and a colour depth of 1 . What is the file size in kilobytes ? [3 ] 5c. An image file has a width of 32 pixels , a height of 21 pixels and a colour depth of 1 . What is the file size in bytes ? [3 ] 6. State what is meant by metadata and give three examples of metadata for a graphics file. [ 3 ] 2.4c - Character Storage Theory Topics 2.4e - Sound Storage

Learn how to add a counter to Greenfoot to keep track of the score. Learn how to add and subtract points to the counter. Part 6 of the Greenfoot Tutorial for the Eduqas / WJEC GCSE 2016 specification. 6. The Counter Greenfoot Tutorial 1. Import the Counter The counter class can be imported into your Greenfoot world. Select Edit in the main Greenfoot window then ' Import Class... ' and choose Counter . Watch on YouTube: The Counter class will appear in the Actor classes list . Right-click on the Counter, choose the ' new Counter() ' option and drag it into the world. Now right-click on the background and select 'Save the World' once you have dragged the counter into the world. 2. Increase the Counter by 1 Two lines of code are required to increase the counter . Add this code when your main character is removing the collectible object . This code allows your main character to access the 'add' method from the Counter class . The method 'add ' just increases the value of the counter by the number in the brackets . To decrease the counter , type a negative value in the brackets, such as -1 . < Part 5 - Play Sounds 3. Compile and Run Click the Compile button at the top of the code editor . Then you can go back to the main Greenfoot window and click Run to test if your counter increases . Click on me if you've got an error that you're stuck with. Part 7 - Extension Ideas >

Learn about the different phases in software development models including planning, requirements, feasibility, design, construction / creation, testing, implementation (phased / parallel / big bang (crash)), documentation creation and maintenance. Based on Unit F160 (Fundamentals of Application Development) for the OCR Cambridge Advanced National in Computing (H029 / H129) (AAQ - Alternative Academic Qualification). Qualification: Cambridge Advanced National in Computing (AAQ) Unit: F160: Fundamentals of Application Development Certificate: Computing: Application Development (H029 / H129) 2.2 - Phases of Software Development Models Watch on YouTube : Phases of Software Development Models There are seven phases of software development models you need to know. As well as knowing the common phases and the key tasks within each phase , you must also understand how and why phases interact with each other and why they may iterate . Phases of Software Development Models Key Phases Planning (including requirements and feasibility ) Design Construction / Creation Testing Implementation (including phased , parallel and big bang ( crash ) methods) Maintenance Documentation creation Phased Parallel Big Bang Q uesto's Q uestions 2.2 - Phases of Software Development Models: 1. Describe the common tasks in each of the first four phases of software development . [8 ] 2. Explain the three implementation methods : phased , parallel and big bang (crash ). [6 ] 3. Describe the common tasks in the final two phases . [4 ] 4. Explain why it is important that phases interact with each other. [ 2 ] Maintenance is important - as of 2025 , some US air traffic control towers still use and maintain systems using Windows 95 and floppy disks because of their reliability . D id Y ou K now? 2.1 - Software Development Models Topic List 3.1 - Planning Projects

Learn about network operating systems, open source operating systems and proprietary operating systems. Resources based on Unit F160 (Fundamentals of Application Development) for the OCR Cambridge Advanced Nationals in Computing (H029 / H129) AAQ (Alternative Academic Qualification). Qualification: Cambridge Advanced National in Computing (AAQ) Unit: F160: Fundamentals of Application Development Certificate: Computing: Application Development (H029 / H129) 1.2 - Operating Systems Watch on YouTube : Network Operating System Open Operating System Proprietary Operating System An operating system is software that manages the resources of a computer system , such as memory , users and files . It also provides a user interface so that humans can interact with the device's hardware . An operating system allows application software to be opened and run . There are three types of operating system that you need to know - network , open and proprietary . Operating Systems Network Operating System (NOS) A network operating system (NOS ) is software that manages network resources and allows computers to communicate over a network . Windows Server , developed by Microsoft , is an example of a network operating system . Characteristics of a Network Operating System Allows for the centralised management of users , data and security across multiple devices on a network . Enables resources such as files , applications and printers to be shared over the network . Manages user authentication and permissions control . Oversees remote access and system monitoring tools . The main type of device that uses a NOS is a server . Other devices, such as desktops or laptops , connect to the server to access shared resources . Windows Server is an example of a popular NOS . Advantages of a Network Operating System Administrators can manage users , files and security on a network from one central location . Resources such as files , printer access and applications can be shared across the network . Access levels can be controlled and user authentication helps protect data . An NOS is scalable - more devices and users can be added as needed . Central servers managed by a NOS make it easier to back up and restore important files . Disadvantages of a Network Operating System Purchasing a NOS and maintaining the servers it runs on can be expensive . Setup and management is complex and may require skilled administrators . If the main server running the NOS fails , connected computers may lose access to resources . Heavy traffic or poor configuration could slow the network down . Who uses a Network Operating System? Application developers can use a NOS to build , test and manage apps that work across networks , such as web applications , multiplayer games or cloud tools . This type of operating system is also used by organisations that need to manage multiple devices , users and resources efficiently across a network , such as a small business or a school . Open Operating System An open operating system is open-source , meaning its source code is freely available for anyone to view , modify and distribute . Source code is the original set of instructions written by a programmer using a high-level language such as Python , Java or C++ . Characteristics of an Open Operating System Users have access to the source code and can see how the OS works . The source code can be modified to suit the specific needs of the user . Development and maintenance may be led by an online community . An open OS is usually free with no licensing costs for most versions. Linux is an example of an open operating system . Android is technically an open-source OS , but most commercial Android devices (like Google Pixel phones ) include proprietary components (like Google Docs or Gmail ), which makes the full system not completely open source . Advantages of an Open Operating System It is usually free to use , modify and distribute the source code . Because the source code can be seen and modified , this type of OS is flexible and customisable . There may be updates from an online community maintaining and improving the software . Promotes experimentation to learn how systems work and try new ideas . Disadvantages of an Open Operating System Programming knowledge and skills are required to modify the source code . There may be security risks if someone edits the source code and redistributes it with malicious code . There will be less official support compared to a proprietary operating system . Some proprietary applications (like Microsoft Access for databases) will only work on a proprietary OS (like Windows ). Who uses an Open Operating System? App developers would use an open OS when the device their application will be used on is not tied to a specific proprietary system (like Windows or MacOS ). For example, a charity making a free educational app for developing countries would choose an open OS so it can run on low-cost , older smartphones . It can be customised and tested on a range of devices . Applications for specific single-purpose systems would also use an open OS , such as an information terminal in a museum . Linux could be used to develop a simple user interface and remove unnecessary features . Proprietary Operating System A proprietary operating system is software that is owned by a company or individual and the source code is not accessible for users to view , modify or distribute . Users must typically buy a licence or agree to the terms of use . Characteristics of a Proprietary Operating System The source code is hidden from the user and cannot be legally modified . A paid licence or subscription is usually required to use the software . It may be maintained and updated by the developer(s) who own it . Only the developer controls updates and the features that are added or fixed . Examples include Microsoft Windows (e.g. Windows 11 ), macOS (for Apple desktops and MacBooks ), iOS (for iPhones ) and iPadOS for iPads ). Advantages of a Proprietary Operating System There is an expectation that it is user-friendly and has been well tested . There may be official support and regular updates for improvements and bug removal . A proprietary OS has a high compatibility with proprietary software such as Microsoft Office or Adobe editing apps . The OS is expected to be stable and secure , with access restricted to system files . Disadvantages of a Proprietary Operating System A paid licence to use the OS is often required , which may be expensive . There is limited customisation for users as the source code cannot be seen or modified . Users rely on the vendor (developer ) for updates and bug fixes . Some proprietary OS are designed to only work on specific hardware (such as iOS only working on iPhones ). Who uses a Proprietary Operating System? App developers will need to use a proprietary OS if they are developing applications for a device that requires a specific proprietary OS , for example if they are creating a game for iPhones , they will need to use iOS . A company designing a finance application on desktops with Microsoft Access and Microsoft Excel must use a proprietary OS like Windows so that it can be integrated with these other types of proprietary applications . Q uesto's Q uestions 1.2 - Operating Systems: 1. What is an operating system ? [2 ] 2. For each of the three types of operating systems , create a poster , information sheet or factfile which includes the following information : Characteristics Advantages Disadvantages Example of how it could be used [10 per OS ] Windows 11 is Microsoft's current operating system . Windows 1.0 was their first release, introduced in 1985 and included basic versions of Calculator , Notepad and Paint . D id Y ou K now? 1.1 - Programs & Applications Topic List 1.3.1 - Application Types