Learn about network devices such as a switch, router, modem and NIC. Also learn about internet terms and services including DNS and the Cloud. Based on the J277 OCR GCSE Computer Science specification (first taught from 2020 onwards). 3.1b: Network Hardware + The Internet Exam Board: OCR Specification: J277 Watch on YouTube : The Internet Network Hardware DNS Servers The Cloud Network Devices When sending data across a network, files are broken down into smaller parts called data packets . Whole files are too large to transfer as one unit so data packets allow data to be transferred across a network quickly . Each packet of data is redirected by routers across networks until it arrives at its destination. Data packets may split up and use alternative routes to reach the destination address. When all the packets have arrived at the destination address the data is reassembled back into the original file. Wireless Access Point A Wireless Access Point provides a link between wireless and wired networks . It creates a wireless local area network that allows WiFi-enabled devices to connect to a wired network. Examples of a wireless access point in a public space could be a WiFi or Bluetooth hotspot , for example a WiFi hotspot in a coffee shop or airport to provide access to the internet. A wireless access point may be a separate device or built into another device such as a router. Router Routers are used to transfer data packets between networks . Routers receive data packets and use the IP address in the packet header to determine the best route to transmit the data. Data is transferred from router to router across the internet towards the destination. A router stores the IP address of each computer connected to it on the network and uses a list called a routing table to calculate the quickest and shortest route to transfer data. Switch A switch is used to connect devices together on a LAN . It receives data packets from a connected node, reads the destination address in the packet header and forwards the data directly to its destination. A switch will generate a list of the MAC addresses of all devices connected to it when it receives data , and must scan for a matching destination address before sending. An alternative to a switch is a hub but a hub is slower and less secure as it forwards a copy of received data to all connected nodes . Network Interface Controller / Card A Network Interface Controller (NIC ) commonly also known as a Network Interface Card is an internal piece of hardware that is required for the computer to connect to a network . The card includes a MAC address which is used when sending data across a LAN . An ethernet cable is plugged into the network card to allow data to be exchanged between the device and a network. A NIC used to be a separate expansion card but is now typically embedded on the motherboar d . Transmission Media Although not technically a device, the communication channel along which data is transferred will affect performance . Three common types of transmission media include: Ethernet cables - used typically on a LAN to transfer data between nodes and hardware such as switches. Examples include Cat5e and Cat6. Fibre Optic cables - very fast but more expensive and fragile cables typically used to send data quickly along a WAN . Data is sent as pulses of light . Coaxial cables - older , slower , copper cables that are not used as much in modern times as they can be affected by electromagnetic interference . The Internet The internet is a global network of interconnected networks . The world wide web (WWW ) is not the same as the internet. It is a way of accessing information , using protocols such as HTTPS to view web pages . Servers provide services on the internet , such as a web server which responds to the web browser (client) request to display a web page . The web server processes the client request to prepare the web page and return it so the web browser can display it to the user . A website must be hosted (stored) on a web server so that it can be accessed by others using the internet . A unique domain name (e.g. csnewbs.com) must be registered with a domain registrar – this is a company that checks the name is valid and not already taken . What is the Internet? DNS Servers A DNS ( Domain Name System ) server stores a list of domain names and a list of corresponding IP addresses where the website is stored. The first thing to understand is that every web page has a domain name that is easy for humans to remember and type in (such as www.csnewbs.com ) as well as a related IP address (such as 65.14.202.32) which is a unique address for the device that the web page is stored on. The steps taken to display a web page: 1. A domain name is typed into the address bar of a browser . 2. A query is sent to the local DNS server for the corresponding IP address of the domain name . www.facebook.com 3. The local DNS server will check if it holds an IP address corresponding to that domain name. If it does it passes the IP address to your browser . 66.220.144.0 4. The browser then connects to the IP address of the server and accesses the web site . If the local DNS server does not hold the IP address then the query is passed to another DNS server at a higher level until the IP address is resolved. If the IP address is found, the address is passed on to DNS servers lower in the hierarchy until it is passed to your local DNS server and then to your browser. Cloud Storage The cloud refers to networks of servers accessed on the internet . Cloud computing is an example of remote service provision . Cloud servers can have different purposes such as running applications , remote processing and storing data . When you store data in 'the cloud', using services such as Google Drive or Dropbox, your data is stored on large servers owned by the hosting company . The hosting company (such as Google) is responsible for keeping the servers running and making your data accessible on the internet . Cloud storage is very convenient as it allows people to work on a file at the same time and it can be accessed from different devices. However, if the internet connection fails , or the servers are attacked then the data could become inaccessible . Cloud Storage Characteristics: ✓ - Huge CAPACITY and you can upgrade your subscription if you need more storage. ✓ / X - Cloud storage is difficult to rank in terms of PORTABILITY , DURABILITY and ACCESS SPEED because it depends on your internet connection. A fast connection would mean that cloud storage is very portable (can be accessed on a smartphone or tablet) but a poor connection would make access difficult . ✓ - Cloud storage is typically free for a certain amount of storage. Users can then buy a subscription to cover their needs - Dropbox allows 2 GB for free or 2 TB for £9.99 a month. Q uesto's Q uestions 3.1b - Network Hardware & Internet: 1a. Explain how a switch works. [ 2 ] 1b. Describe the purpose of a router . [ 2 ] 1c. State what WAP stands for and why it is used . [ 2 ] 1d. State what NIC stands for and why it is required . [ 2 ] 1e. State the differences between the three main types of transmission media . [ 3 ] 2a. State what the internet is and how it is different to the world wide web . [ 2 ] 2b. What is web hosting ? [ 2 ] 3a. What is a DNS server ? [ 2 ] 3b. Describe, using a mix of text and icons / images , how a DNS server is used to display a web page . [5 ] 3c. Describe how a DNS server searches for an IP address if it is not found on the local DNS server . [ 2 ] 4a. Describe what cloud computing is. [ 2 ] 4b. State two advantages and two disadvantages of the cloud . [ 4 ] 3.1a - Network Types & Performance Theory Topics 3.2a - Wired & Wireless Networks

Learn about different formats for presenting data on the internet including webpages, blogs, streamed video and audio, document stores and RSS feeds. Based on the 2016 OCR Cambridge Technicals Level 3 IT specification for Unit 2 (Global Information). 1.6 - Information Formats Exam Board: OCR Specification: 2016 - Unit 2 The following formats are used to display information on the internet . Web Pages Web pages can be used for a diverse range of purposes including advertising products, reporting information , displaying images and eCommerce (online shopping). There are two types of web page: Static web page Static web pages contain content that is pre-built and remains the same each time the page is loaded . Static web pages are cheaper and easier to create and load quicker ; they use basic HTML. It can be changed by the site editor but will appear the same for everyone who has access to it, such as a classic promotional website for a small company. Dynamic web page Dynamic web pages are generated when they are loaded and can appear different to different users . Dynamic web pages are harder to code but they can be linked to databases to allow them to show personalised content to whoever is viewing the site; they are written in server-side languages like PHP. The Amazon homepage is an example of a dynamic web page as personalised deals based on previous user history will be shown if you are logged in with an account. Blogs Blogs are used to share information with like-minded individuals, such as those who enjoy the same hobbies or beliefs . Charities , game developers and other businesses also use blogs as a way of updating their customer base with what they have done or what they are working on. Blogs can feature multimedia such as text, images, videos and links to other sites. Advantages of Blogs Disadvantages of Blogs ✓ Share information with followers in the format of text, images and video . ✓ Blogs and vlogs can unite people with similar interests , such as a cookery blog or travel vlog. X Takes a lot of effort and time to create posts, especially if videos need to be edited before posting. Potential customers could be lost if blogs aren't updated regularly . X It can be difficult to build up a customer base directly from a blog. Posts must be engaging , researched and correct . Podcasts A podcast is a downloadable audio file , usually on a certain topic such as sports or gaming that can be listened to when convenient for the user. Spotify and Apple Music have a wide library of podcasts. Advantages of Podcasts Disadvantages of Podcasts ✓ Podcasts are not (usually) recorded live , so they can be edited and uploaded at a certain time each week. ✓ Podcasts can be listened to when convenient for the user, so they can't 'miss' it and can catch up when is best for them. ✓ Podcasts are becoming more and more popular , so the possible audience base is growing each year. Celebrity guests are one way to entice more listeners. X Takes time to record a podcast, especially if they need to be edited to add in music or sound effects or to remove mistakes . X It can be difficult to build up an audience directly from a podcast. Podcasts should be on a topic that interests people and spoken in an engaging way. Streamed Audio & Video Streaming is the process of receiving video / audio data in a continuous flow . This allows the user to access the video / audio immediately , without having to wait for the file to download entirely. For example, the BBC provide live radio streaming online for their radio shows and BBC iPlayer allows users to watch 'catch up' programs that previously aired. YouTube is a widely-used streamed video platform and Spotify is a popular streamed audio service. Advantages of Streamed Media Disadvantages of Streamed Media ✓ Streaming does not require data to be downloaded entirely before use - users can watch / listen as soon as the connection starts . ✓ Streaming is harder for users to share than downloading a file . Netflix uses this as a form of piracy protection . X Streaming requires high bandwidth so users may suffer performance issues on slower devices and networks . X Streaming requires a constant network connection compared to downloadable media which can be used when offline / outside. Social Media Channels Social media channels provide a huge amount of data on users in an informal space. Organisations can receive feedback through user posts and comments . Real-time statistics like views, likes and shares provide an insight to user opinion . Social media channels include traditional sites such as Facebook and Twitter as well as business and recruitment platforms such as LinkedIn . Discussion boards and forums , such as Reddit , are increasingly popular for users to discuss similar hobbies and interests such as politics, gaming and healthy eating. Advantages of Social Media Disadvantages of Social Media ✓ Social media can increase a business' online presence as it is online 24/7 for users to comment and interact with posts. ✓ Posts can be shared between users and their contacts, allowing a post to 'go viral' and be seen by potentially millions of viewers . ✓ Posts can be shared in different information styles such as text , images , video or hyperlinks to other websites. ✓ Businesses can use social media to communicate with their customer s , such as direct messages on Facebook if a customer is unhappy. X Businesses may need to hire a social media manager to interact with customers , update posts and remove spam. X Negative posts can be shared and spread very quickly , such as if a customer complains about how a business treated them poorly. X Businesses must be cautious about what they post , to not accidentally offend others and damage their reputation . Emails Emails can be used to provide information to a large amount of people almost instantly . A company may use an email to advertise new products , inform potential customers of a marketing promotion or target specific users based on previous interactions. Advantages of Emails Disadvantages of Emails ✓ Faster (almost instant) and cheaper (usually free) to send an email compared to traditional letters . ✓ Files can be attached to the email, such as images, videos or forms to complete. ✓ An audit trail can be kept, recording communication between the company and its customers. ✓ Emails can be sent, delivered and read at the user's convenience and to any internet-enabled device across the world . X An internet connection is required to open and read the email. Larger attachments may not open on mobile devices. X Malware can spread through email attachments. Phishers use emails to gain access to personal information and account details . X Some attachments sent via email may be unreadable on different devices / operating systems. X Emails may automatically go into the spam / junk folder and be deleted without being read . Document Stores Document stores allow users to store online files in cloud storage . Common services are Google Drive , Dropbox and Microsoft's OneDrive . Storing documents in the cloud allows users to edit and access them from any location with an internet connection and opens up opportunities for collaboration . Many organisations offer cloud storage space for free up to a certain amount before charging customers for more data. Document stores are very convenient for users and replace the need for portable storage devices like USB sticks. Teachers can use documents stores to share resources with other staff in a school . Documents stores can only be accessed with an internet connection so files will be unavailable during maintenance or network failure. Users rely on the cloud hosting provider, such as Microsoft and Google to keep the data secure and available . RSS Feeds RSS Feeds (short for Rich Site Summary ) allow users to subscribe to updates from their favourite websites. It is a web feed that updates whenever a subscribed site releases new information. For example, the BBC used to post updates for important news headlines which appeared in a subscribed user's RSS feed. As of 2020 most browsers no longer have built-in RSS functionality and it is rarely used . Q uesto's Q uestions 1.6 - Information Formats: 1. Describe the difference between static and dynamic web pages . [4 ] 2. For each type of information format describe its advantages and disadvantages . a. Blogs [8 ] b. Podcasts [8 ] c. Streamed Audio / Video [8 ] d. Social Media [8 ] e. Emails [8 ] 3. Explain how document stores could be used by organisations and individuals . [4 ] 4. Explain what an RSS feed is and how an organisation could use it . [3 ] 1.5 - WWW Technologies Topic List 1.7 & 1.8 - Internet Pros & Cons

Learn about two important expansion cards that can be connected to the motherboard - graphics cards and sound cards - and how they work. Expansion Cards PCI slots What are expansion cards? Expansion cards are additional components that you plug into the motherboard’s expansion slots to add or enhance features . The slots are called PCI (on older computers ) or PCIe (on newer models ). Common types are graphics cards (video ), sound cards (audio ), network cards (internet ) and capture cards (streaming ). Graphics Card A graphics card processes images , videos and 3D graphics so they look smooth and realistic . It is used for gaming , video editing , 3D modelling and Virtual Reality (VR ). It has its own processor - the Graphics Processing Unit (GPU ) - and dedicated memory (VRAM ), so it doesn’t overload the CPU or RAM . Modern graphics cards can also handle tasks like artificial intelligence (AI ) and bitcoin mining . Graphics cards usually have a cooling system, like a fan , so it doesn't overheat. The graphics processing unit ( GPU ) is a chip that renders images and video. The graphics card has ports such as HDMI or DisplayPort to connect monitors or TVs. The PCIe connector allows the graphics card to slot onto the motherboard. Sound Card The DAC ( Digital-to-Analogue Converter ) converts digital data (1s and 0s) from the computer into analogue sound waves for speakers/headphones. The ADC ( Analogue-to-Digital Converter ) converts analogue input (like voice from a microphone) into digital data the computer understands. Jacks are small round sockets where you plug in audio devices like headphones, microphones, or speakers. The PCIe connector allows the sound card to slot onto the motherboard. A sound card improves the quality of audio input/output compared to the motherboard’s built-in sound . They are not needed by most users , because of the motherboard's built-in sound , but they are used by music production , gaming or professional audio work . It can support surround sound systems , high-quality microphones , and musical instruments using jacks (audio ports ). Integrated cards Built directly into the motherboard . Cheaper , uses less power and is good enough for basic tasks (e.g. web browsing , watching videos and office work ). Shares the computer’s RAM and processor (CPU ) instead of having its own . An example is integrated graphics on a laptop for browsing and schoolwork . Dedicated cards These are separate expansion cards (e.g. graphics card or sound card ) to connect to the motherboard 's PCIe slots . They usually have their own processor and memory (e.g. GPU & VRAM for graphics ). Much more powerful , ideal for gaming , video editing , 3D design or professional audio . Uses more power and costs more . KS3 Home

Test your understanding of printing, comments and variables. Try practice tasks and learn through text and images. Perfect for students learning GCSE Computer Science in UK schools. top Python - Section 1 Practice Tasks Task One: Weekdays Create a program that prints all 5 weekdays , with each day on a new line . Requirements for a complete program: Use only one print line - use \n . No empty space at the start of a printed line. Example solution: Monday Tuesday Wednesday Thursday Friday Task Two: Colour & Animal Sentence Write a program that uses two variables , one for a colour and one for an animal . Print a sentence using both variables . Requirements for a complete program: Use both your variables within one print line. Include capital letters, appropriate punctuation and no irregular spacing in the printed line. Remember: Break up variables in a print line by using commas or plus signs between each part of the "sentence" . Example solutions: Have you ever seen a purple cat? A horse that was green galloped past! Three yellow ants ate my lunch. Task Three: Number, Adjective & Animal Write a program that uses three variables , a number , an adjective (descriptive word) and an animal . Print a sentence using all three variables . Requirements for a complete program: Use all three variables within one print line. Include capital letters, full stops and no irregular spacing in the printed line. Remember: Break up variables in a print line by using commas or plus signs between each part of the "sentence" . Example solutions: What? 64 sneaky elephants just ran past me! There were 12 hungry bears in the park. 85 patient spiders waited in the corner. ⬅ 1d - Using Va riables 2a - Inputting Text ➡

Learn about the motherboard, graphics processing unit (GPU), sound card, embedded systems and input / output systems. Based on the 2020 Eduqas (WJEC) GCSE specification. 1.6: Additional Hardware Exam Board: Eduqas Specification: 2020 1.6a - Internal Hardware Motherboard The motherboard is the main circuit board of a computer , unique for each device. It holds and connects the different components together , allowing data to be transferred between them. Components such as the CPU and ROM are directly attached to the motherboard. The motherboard has expansion slots for additional cards (i.e. sound cards) and ports (i.e. USB). Graphics Processing Unit (GPU) Sound Card A GPU is a microprocessor that performs complex calculations to generate graphical images to be displayed on a monitor . There are two types of GPU, integrated GPUs within the motherboard circuitry or dedicated GPUs on an additional card (known as a 'graphics card'). An integrated GPU is cheaper and generates less power because it uses the RAM of the computer . Integrated GPUs are used in tablets and laptops as they generate less heat and are optimal for general computing uses (e.g. web browsing or watching movies). A dedicated GPU is more expensive and generates more heat, often requiring a fan because it contains its own memory . Dedicated cards are used by animation professionals and professional gamers who require the best graphics. Sound cards convert analogue sound waves into digital data (binary) when inputting audio through a microphone. 0010 1011 0101 0101 0110 0111 0101 0001 0101 0010 1011 0101 0101 0110 0111 0101 0001 0101 Sound cards also convert digital data (binary) into analogue sound waves to output audio through speakers or headphones. 1.6b - Embedded Systems Example: A washing machine has a control chip that manages the different program cycles. An embedded system is a computer system built into a larger machine to provide a means of control . Embedded systems perform a specific pre-programmed task which is stored in ROM . An embedded system uses a combination of hardware and software . Example: A traffic light has a control chip that determines when to change to a green or red light. 1.6c - Input & Output Devices Input devices are used by humans to interact with a computer system , through methods such as text , voice or touch . Output devices show the result of computer processing , such as sound , printed text or a visual display on a monitor. Storage devices , such as a USB stick or an external hard drive, are neither input nor output devices - see 1.4 . Input Devices These are just some of the more common input devices . A mouse and a keyboard have been described in further detail. Are there any devices below you haven't heard of before? Mouse Benefits: Easy to navigate a graphical user interface. A wireless mouse takes up less space . Faster to select options (e.g. in a video game). Drawbacks: Difficult to use for people with restricted hand movement . Difficult to use on some surfaces . Other input devices: Scanner Controller Microphone Webcam Chip Reader OCR Scanner OMR Scanner Barcode Scanner Graphics Tablet Sensors (e.g. light or temperature) Touch Screen Remote Control Biometric Scanner (e.g. fingerprint or iris) Concept Keyboard Sip / Puff Switch Keyboard Benefits: Quick to input text . Easy to use with a familiar layout on most keyboards. Keys can be customised and shortcuts can be used . Drawbacks: Takes up a large amount of space on a desk. Difficult for people to use with restricted hand movement or poor eyesight . Output Devices Monitor These are just some of the more common output devices . A monitor and a printer have been described in further detail. Are there any devices below you haven't heard of before? Other output devices: Plotter Speakers Projector Alarm Light Headphones Touch Screen Braille Terminal What is it? A monitor is required to see the result of human input and computer processing . Monitors can be bought in different sizes and resolutions for a range of purposes such as video editing or playing games . Monitors settings can be changed to alter the brightness or contrast . Printer What is it? A printer uses ink or toner to print a document (such as text or images) onto paper . Inkjet printers use ink cartridges , are generally slower and print in a lower quality . Laser printers use toner cartridges and are generally quicker and print to a higher quality . Q uesto's Q uestions 1.6 - Additional Hardware: 1.6a - Internal Hardware 1. What is the purpose of the motherboard ? [2 ] 2a. What is the purpose of the GPU ? [ 2 ] 2b. Describe two differences between integrated and dedicated expansion cards . [ 4 ] 3. Explain how a sound card works. [ 4 ] 1.6b - Embedded Systems 1. What is an embedded system ? [3 ] 2a. Give two examples of an embedded system. [ 2 ] 2b. Research and describe another example of an embedded system. [ 2 ] 1.6c - Input & Out[ut Devices 1. Choose four input devices and describe at least two benefits and two drawbacks of using each one. [ 8 ] 2. Describe three output devices . [ 3 ] 3. Justify which input and output devices would be most suitable in the following scenarios: a. A teacher needs to take the class register . [ 4 ] b. A family want to communicate with their cousins in Australia. [ 4 ] c. The school movie club wants to play Star Wars in the assembly hall. [ 4 ] d. An e-sports player is taking part in an online multiplayer tournament . [ 4 ] e. A laboratory needs security so that only registered scientists can enter. [ 4 ] 1.5 - Performance 2.1 - Logical Operators Theory Topics

Learn how to create and use procedures in Python. Try practice tasks and learn through text and images. Perfect for students learning GCSE Computer Science in UK schools. top Python 7a - Procedures Subroutines A subroutine is a section of code that can be re-used several times in the same program. It is separate from the main code and has to be ‘called’ upon. Subroutines are designed to be repeated, and they have three key benefits: Subroutines make programs easier to read . They reduce the duplication of code . Complex problems are broken down into smaller chunks . There are two types of subroutines: procedures and functions . A procedure just executes commands , such as printing something a certain number of times. A function produces information by receiving data from the main program and returning a value to the main program. For example, a function could take the radius of a sphere from the main program, calculate a sphere’s area and return the value of the area to the main program. A function generally requires parameters to work – these are the values to be transferred from the main program to the subroutine. Procedures A procedure i s a type of subroutine that runs independently of the main program . A subroutine must be defined at the top of the program before the main code by typing def and the name of the subroutine . In the example below I have created a procedure to calculate the multiplication of two numbers and a separate procedure for the division. The main program starts beneath the subroutines , against the left side of the editor. I have created a while true loop that asks the user if they want to multiply, divide or stop the program. If they choose to multiply, the multiply subroutine is called . This initiates that subroutine then returns to the main program when it is complete. If they choose to divide, the divide subroutine is called instead. Typing stop will break (end) the loop. Here you can see the two parts of the program put together. Subroutines must be written first , with the rest of the program underneath. Subroutines can be called in any order . Below I have run the program and divided then multiplied before breaking the loop: Practice Tasks 1 1. Create a procedure called hello that just prints “Hello there! ”. In the main program create a for loop that calls the procedure 10 times. You must use a procedure. 2. Create a program with two procedures. The addition procedure allows the user to add two numbers together. The subtraction procedure allows the user to take a number away from another. Use a while true loop in the main program and a break to stop the loop. Example solution for #1: Local & Global Variables Programming languages use local variables and global variables . A global variable can be used anywhere in the program . A local variable can only be used in the subroutine it is created in . I have adapted the multiply / divide program below to use global variables by stating the global command and the name of the variables in each subroutine. This allows me to ask the user to enter numbers in the main program. Practice Tasks 2 1. Adapt your addition / subtraction program from the first practice task section to use global variables. 2. Create a program that asks the user to enter their name in the main program. Call a subroutine that greets the user using the name variables. You must use a procedure and a global variable . Example solution for #2: ⬅ Section 6 Practice Tasks 7b - Functions ➡

Learn about the decomposition methods used in project planning such as abstraction, pattern recognition, modularisation (top down and bottom up) and parsing of requirements. 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) 4.3 - Decomposition Methods Watch on YouTube : Abstraction Pattern Recognition Modularisation Parsing of Requirements Decomposition methods break complex problems or systems into smaller , more manageable parts . This makes development easier to plan , understand and implement . Decomposition also helps reduce errors and improve efficiency , as individual tasks can be more easily tested and debugged. For each of the four decomposition methods ( abstraction , pattern recognition , top-down and bottom-up modularisation and parsing requirements ) you need to know when each method is suitable to use , its advantages and disadvantages , how client requirements affect their selection and how they can be used to visualise application designs . Decomposition Methods Abstraction Abstraction is the process of simplifying a problem by ignoring irrelevant data and focusing only on the most important details . It is used in the early stages of design or planning , when managing complexity in large systems and when creating reusable components . Pattern Recognition Pattern recognition is used to identify similarities or trends in problems or client requirements . This allows for the reuse of existing components and aids in finding solutions for common issues . It is used during the planning or analysis phases and when dealing with similar tasks , inputs , outputs or processes . Modularisation Modularisation refers to the individual components that make up a larger project . In top-down modularisation , a larger system is broken down from a general overview into its most specific parts . The purpose of bottom-up modularisation is to build the system starting with the smaller , detailed components and combining them into larger subsystems . Parsing of Requirements To parse requirements means to systematically break down and analyse client requirements into actionable tasks or functions . It is used at the start of a project to ensure shared understanding between development teams and clients . Q uesto's Q uestions 4.3 - Decomposition Methods: 1. Explain the differences between top-down and bottom-up modularisation . [4 ] 2. Explain when abstraction would be an appropriate decomposition method to use. [3 ] 3. What are the advantages and disadvantages of parsing requirements ? [ 4 ] 4. Give one way each decomposition method can be used in software application development . [ 4 ] Alan Turing and his team used pattern recognition to analyse recurring sequences in encrypted German messages , helping to break the Enigma code , which was a major factor in the Allies’ victory in World War II . D id Y ou K now? 4.2 - Client Requirement Specs Topic List 5.1.1 - Human-Computer Interaction

Learn about the factors that affect the performance of networks, as well as different types of network types such as LAN and WAN. Based on the J277 OCR GCSE Computer Science specification (first taught from 2020 onwards). 3.1a: Network Types & Performance Exam Board: OCR Specification: J277 Watch on YouTube : LAN & WAN Network Performance Client-Server Network Peer-to-Peer Network Star Topology Mesh Topology What is a network? A network is more than one computer system connected together allowing for communication and sharing of resources . 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 Wide Area Network 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.bbc.co.uk 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. 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: 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. 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. 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 . The network infrastructure of a LAN (such as servers and routers) is usually owned and managed by the network owner . A wide area network (WAN ) has computer systems situated geographically distant to each other, possibly across a country or even across the world . WANs often use third party communication channels , such as connections by internet services providers like BT or Virgin Media. Data Packets When sending data across a network, files are broken down into smaller parts called data packets . Whole files are too large to transfer as one unit so data packets allow data to be transferred across a network quickly . Each packet of data is redirected by routers across networks until it arrives at its destination. Data packets may split up and use alternative routes to reach the destination address. When all the packets have arrived at the destination address the data is reassembled back into the original file. What is a network topology? Network topology refers to layout of computer systems on a local network . Devices in a network topology diagram are often called 'nodes' . Two types of typology are star and mesh . Star Topology Each computer system is connected to a central device , usually a hub or switch . How it works: Each computer system is connected to the central hub or switch and transfers its data packets there. The hub or switch looks at the destination address and transfers the packets directly to the intended computer. 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 full mesh network, each computer system is connected to every other computer system . There is also a partial mesh network where only some nodes (e.g. a printer) are connected to every other node. 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 full 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 . Performance There are several different factors that can affect the performance ( speed ) of a network, such as: The bandwidth available * Interference (e.g. thick walls) Number of users at the same time Distance to travel / signal strength Number of data collisions Amount of data to transfer * Bandwidth is the maximum amount of data that can be sent across a network at once . Q uesto's Q uestions 3.1a - Network Types & Performance: 1a. Describe the difference between a LAN and WAN . [2 ] 1b. Give an example of how a LAN and a WAN could each be used . [ 2 ] 2 a. Describe how peer-to-peer networks and client-server networks function. 2b. Give one use for both types of network. 3. Draw and label diagrams of client-server , peer-to-peer , star and mesh networks. [8 ] 4. An office currently uses a star topology but is considering changing to a mesh topology . Describe two advantages and two disadvantages of both topologies. [ 8 ] 5. State five factors that could affect the performance of a network . [5 ] 2.5 - Compression 3.1b - Network Hardware & Internet Theory Topics

Learn how to read and search through files in Python. Try practice tasks and learn through text and images. Perfect for students learning GCSE Computer Science in UK schools. Python 10b - Read & Search Files Reading from a File To read and print from a file you must open it in read mode by typing "r" instead of "a". If you are writing and reading in the same program, make sure you close the file in append mode before you open it in read mode . The program below uses the Customers.txt file from the last section. A simple for loop can be used to print each line of the file. The end = "" code just prevents a space between each line. Practice Task 1 Open one of the files that you used in Section 10a and print each line. Example solution: Reading Specific Lines from a File Sometimes it is necessary only to print certain lines. The following example uses a file where I have written a sentence of advice on each line. The user is asked to enter a number between 1 and 6. If they enter 1, the first line of the file is printed. If they enter 2, the second line of the file is printed etc. Remember Python starts counting everything at 0 so each line is a digit less than you would expect . Square brackets must be used to denote the line to print: [1] not (1). The end = "" code is not necessary but removes space after the line. Practice Task 2 Create a text file (saved in the same folder as your Python file) with a list of video games. Ask the user to enter a number between 1 and 10. Print the line for the number that they input. Example solution: Print a Random Line The randint command can be imported and used to print a random line from a file . The example below prints one of the 12 months . The file is opened in read mode and the readlines() command extracts each line , placing them in a list . A random number is then generated between 0 and one less than the total number of lines . This random number is then used to print a line from the extracted list of lines . Python code from random import randint file = open ( "months.txt" , "r" ) lines = file.readlines() random = randint(0,11) print (lines[random]) months.txt January February March April May June July August September October November December potential outputs March December April July If the length of the file is not fixed (e.g. new lines are being added or lines removed ) then the random number generation line can be adapted to use the len command to calculate the current number of lines . This is required to know the upper limit of the random number . random = randint(0,len(lines)-1) Searching Through Files A for loop is used to search through a file , line by line . First, an input line is used to allow the user to enter their search term . If the term that is being searched for is found, then the whole line is printed. The example below uses a variable named found to state if there is a match when the file is searched. If the search term is found, then the found variable is changed to true . If the search term is not found , the found variable remains as false, so the 'no customers found' statement is printed . Practice Task 3 You should have completed Practice Task 2 from Section 10a (the A Level task). Add extra code to that program so that you can search for specific students. Example solution: ⬅ 10a - Open & Write Files 10c - Remove & Edit Lines ➡

Learn how to handle strings (text) in Python. Try practice tasks and learn through text and images. Perfect for students learning GCSE Computer Science in UK schools. top Python 9a - String Handling What is String Handling? String handling refers to the manipulation of a string variable , typical uses include: Checking the length of a variable. Searching a variable for a certain phrase. Checking the number of times a specific character or word is used . String handling is used to examine passwords and to ensure that they are of an acceptable strength (e.g. by checking that they are at least 8 characters in length and include a mixture of capital letters , lowercase letters and symbols ). Password: arsenal Password: $tr0nG_pA$$w0rd Lowercase & Uppercase .lower() and .upper() are functions that convert a string into a fully lowercase or uppercase version. dogbreed = "Chihuahua" print (dogbreed.upper()) CHIHUAHUA character = "sPoNgeBoB" print (character.lower()) spongebob You may have realised that Python is very specific . 'yes ', 'Yes ' and 'YES ' are all treated as different values . Converting user input into one case , such as lowercase, and then comparing that input is a better way of checking an input than having an if statement with multiple or comparisons. The program below converts the user input into lowercase to compare. 'yes', 'Yes' and 'YES' are all converted to 'yes'. answer = input ( "Would you like water? " ) answer = answer.lower() if answer == "yes" : print ( "I'll fetch you a glass." ) else : print ( "Don't dehydrate!" ) Would you like water? yes I'll fetch you a glass. Would you like water? Yes I'll fetch you a glass. Would you like water? YES I'll fetch you a glass. Practice Task 1 Ask the user to enter their first name and surname. Print their surname in uppercase followed by their first name in lowercase. Example solution: Enter First Name: Jayden Enter Surname: Hargrove Welcome HARGROVE, jayden Count Characters The easiest way to count how many times a certain value appears within a string is to use the .count() command. It is important to note that, just like when using an input statement or calculation line, you must save the calculation into a variable . An example, for counting the number of e’s in a sentence, is below: sentence = input ( "Enter your sentence: " ) e_count = sentence.count( "e" ) print ( "There were" , e_count, "e's in your sentence!" ) Enter your sentence: even ellie eats elderberries There were 9 e's in your sentence! Practice Task 2 Create a program that counts how many instances of the letter a have been entered in a sentence. Bonus: Use the .lower() function in your code to include capital letters. Example solution: Enter a sentence: An angry aardvark named Aaron. That sentence had 8 a's. Finding the Length of a String Just like when we wanted to find the length of a list, we use the len command to see how many characters are in a string . It is sensible to save the result of the function into a variable so it can be used later . fruit = input ( "Enter a fruit: " ) length = len (fruit) print ( "That fruit was" , length, "characters." ) Enter a fruit: pineapple That fruit was 9 characters. A common reason for finding the length is as part of validation , for example, checking a password is more than 8 characters : password = input ( "Enter a new password: " ) length = len (password) if length >= 8: print ( "Password accepted!" ) else : print ( "Password is too short, must be at least 8 characters." ) Enter a password: snake54 Password is too short, must be at least 8 characters. Enter a password: pebblesthedog76 Password accepted! Practice Task 3 Create a program that asks for a name. Check that the name is between 4 and 10 characters. Print appropriate messages if it is within this range and if it isn't. Example solution: Enter a name: Tom That name is too short, it must be between 4 and 10 characters. Checking the Start / End of a String To determine if the first character in a string is a specific value use the .startswith() command. .startswith() is a function that will return True or False . Below is an example program to check if a name begins with the letter L . name = input ( "Enter a name: " ) if name.startswith( "L" ) == True : print ( "I like that name." ) else : print ( "I don't like that name." ) Enter a name: Lionel I like that name. Enter a name: Katjaa I don't like that name. Similarly, you can use .endswith() to check the last characters of a string . Practice Task 4 Ask the user to enter a country. Print a message if it ends with 'land', 'stan' or any other ending. Use .endswith() Example solution: Enter a country: Finland You have entered a 'land' country. There are 9 in the world. Enter a country: Kyrgyzstan You have entered a 'stan' country. There are 7 in the world. Enter a country: Peru Thanks for your entry. Note: You don't need to check if it's a valid country. Reversing a String To reverse a string, you write the variable name and then use square brackets to move one character at a time backwards. The first two colons are left empty as they denote where to start and end from (which don’t need to be changed). Therefore the -1 states that it will reverse from the end to the start : Ask the user to enter a random sentence. Print the sentence in reverse. Example solution: Practice Task 5 Printing Parts of a String You may want to print just part of a string or variable using square brackets. You can also use len to work out the length and work back, if you want to display the last characters: Practice Task 6 Ask the user to input a long word. Output the middle character of the word. Example solution: Split Strings Use the .split command to split a string into separate words . An empty split command such as words.split() will split at each space . You can enter a value in the brackets to split at certain characters , such as words.split(",") Use the len function to count the number of words once they have been split. You can use a for loop to cycle through each word. The program below checks the length of each word . Practice Task 7 Ask the user to input a sentence. Calculate and print the amount of words in the sentence. Calculate and print the amount of words that begin with s. Example solution: ⬅ Section 8 Practice Tasks 9b - Number Handling ➡

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 5 Collection of Colours A new paint company , 'Sparkle and Shine Paint Schemes ' needs a program that can manage the different colours they sell to customers. They currently have a file with many different colours and want a program made with features to add, remove and list the different colours . 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. Reminders for this task: You will need to create a selection of options for the user to choose from. Subroutines and a while true loop may help. Section 10 will help you to open, write and read from files . Section 10c shows how to remove lines from a file. There are multiple ways to approach this program, and your solution might look different from the example. Break the problem down and focus on one part at a time. Example solution: Use a menu to select the different options using a command word. Download the colours file: Selecting Total will list the number of colours in the file. This should change whenever a new colour is added or one is removed . Selecting Add will allow the user to enter the name of a new colour to be added to the file . Selecting Letter will allow the user to enter a letter . All colours beginning with that letter should be displayed . Selecting Remove will allow the user to enter a colour to be removed from the file . Selecting Random will display a random colour from the file. Selecting End will stop the program. ⬅ Extended Task 4 (Vet Surgery) Extended Task 6 (Word Game) ➡

Learn about the tags in the head section of an HTML document including the title and meta tags. 7. Head Tags HTML Guide Watch on YouTube: Remember that all HMTL documents are split into the head and the body. The following tags must be typed inside of your head tags . title Title The title is not the main heading. The title is the page title itself that you can see at the tab at the top of your web browser. Add a title to your web page. metadata Metadata Metadata is information about the web page itself. This commonly includes data about the author, the page's contents and any keywords. Metadata will not appear on the actual web page . Add meta data tags between your head tags for author, keywords and a description. The meta tag is made up of a name and content . Author represents who created the web page. Keywords are commonly used words. Description is used for displaying search engine results (such as a Google search). Next it is time to embed YouTube videos into your web page. 6. Organisation Tags HTML Guide 8. Videos