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3.2: Data Packets & Switching Exam Board: Eduqas / WJEC Specification: 2020 + What is a data packet? 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. Contents of a Data Packet Data packets contain six distinct pieces of data which are used to redirect the packets towards the destination address. Packet Switching vs. Circuit Switching The key difference is that a circuit-switched network sends data along the same route . A packet-switched network sends data packets along different routes . Packet Switching With a packet-switched network the data is split into packets . The data packets are transmitted over a network and may take different routes to its destination. When all the packets have arrived the data is reassembled . The Internet is an example of a packet-switching network. Advantages of Packet Switching: Transmission is more secure as it is harder for a hacker to intercept complete data because it can take different routes . If a network device fails the data packets can take an alternative route . Data packets can be sent efficiently and individually across less busy routes . Disadvantages of Packet Switching: ​ Reassembling the data takes longer because packets may arrive out of order . It is less reliable than circuit switching as some data packets may not reach the destination (this is called packet loss ). Circuit Switching When data is transmitted over a circuit-switched network all of the data takes the same route to the destination address in one continuous stream . The data is quickly reassembled at the destination because it is already in the correct order . The old telephone system is an example of a circuit-switched network. Advantages of Circuit Switching: ​ Reassembling the data is quick because the packets arrive in the order that they were sent. It is more reliable than packet-switching because data is sent in one continuous stream . The transmission is fast and should encounter fewer errors - once the connection has been securely established . Disadvantages of Circuit Switching: Less secure as hackers could intercept the data and more easily access the data as it all takes the same route. Establishing a connection takes time to set up. If any device fails on the route then the whole connection breaks and data transfer will be incomplete. Q uesto's Q uestions 3.2 - Data Packets & Switching: ​ 1. Draw the data packet diagram and label all 6 pieces of information . [ 6 ] ​ 2a. Describe how packet switching works . [3 ] 2b. Describe the advantages of packet switching . [3 ] 2c. Describe the disadvantages of packet switching . [2 ] ​ 3a. Describe how circuit switching works . [3 ] 3b. Describe the advantages of circuit switching . [3 ] 3c. Describe the disadvantages of circuit switching . [3 ] 3.1 - Network Characteristics Theory Topics 3.3 - Network Topology

Exam Board: OCR 4.1c - Signed Binary & Floating Point Specification: A-Level 2015 An instruction set is a list of all the instructions that a CPU can process as part of the FDE cycle . ​ CPUs can have different sets of instructions that they can perform based on their function. The two most common instruction sets are the simpler RISC (Reduced Instruction Set Computer ) and more complicated CISC (Complex Instruction Set Computer ). Instruction Sets This page is still being updated. Graphical Processing Unit What is cache memory? ​ Cache memory is temporary storage for frequently accessed data . ​ Cache memory is very quick to access because it is closer to the CPU than other types of memory like RAM . Multicore & Parallel Systems What is cache memory? ​ Cache memory is temporary storage for frequently accessed data . ​ Cache memory is very quick to access because it is closer to the CPU than other types of memory like RAM . Multicore & Parallel Systems What is cache memory? ​ Cache memory is temporary storage for frequently accessed data . ​ Cache memory is very quick to access because it is closer to the CPU than other types of memory like RAM . Q uesto's Q uestions 4.1c - Signed Binary & Floating Point: ​ 1. What is cache memory ? [ 2 ] ​ 4.1b - Denary, Binary & Hexadecimal Theory Topics 4.1d - Binary Calculations

Extended Task 7 'Guess the Number' Multiplayer Game A primary school teacher wants to create a fun activity for their students to play when it is raining and they have to stay inside during break and lunch. Five pupils can play the game at once. Each player chooses a number between 1 and 100 . Then a random number is generated. ​ Whoever was furthest from the random number is out of the game . The four remaining players then pick a new number . This continues with one player being removed each round until only one player is left and they are the winner. ​ Add your own flair and additional features to your program as an extension, including preventing the same number being chosen by multiple players . 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 use loops to allow the users to enter their numbers. You may wish to use subroutines to decompose the problem into separate rounds. You will need to import the random library to generate a random number in each round. You will need to compare each number to the randomly selected answer using comparison operators such as > and <. 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: Introduction & Round One Round Two ⬅ Extended Task 6 (Word Game)

Exam Board: OCR 3.1a - Compression Specification: A-Level 2015 An instruction set is a list of all the instructions that a CPU can process as part of the FDE cycle . ​ CPUs can have different sets of instructions that they can perform based on their function. The two most common instruction sets are the simpler RISC (Reduced Instruction Set Computer ) and more complicated CISC (Complex Instruction Set Computer ). Instruction Sets This page is still being updated. Graphical Processing Unit What is cache memory? ​ Cache memory is temporary storage for frequently accessed data . ​ Cache memory is very quick to access because it is closer to the CPU than other types of memory like RAM . Multicore & Parallel Systems What is cache memory? ​ Cache memory is temporary storage for frequently accessed data . ​ Cache memory is very quick to access because it is closer to the CPU than other types of memory like RAM . Multicore & Parallel Systems What is cache memory? ​ Cache memory is temporary storage for frequently accessed data . ​ Cache memory is very quick to access because it is closer to the CPU than other types of memory like RAM . Q uesto's Q uestions 3.1a - Compression: ​ 1. What is cache memory ? [ 2 ] ​ 2.4c - Object-Oriented Language Theory Topics 3.1b - Encryption & Hashing

Links: Installing Greenfoot Greenfoot Game Tutorial Glossary of Key Code Help with Errors I'm Greta the Gecko and I'm here to teach you Greenfoot.

6.1b: Legislation Exam Board: OCR Specification: 2020 Data Protection Act (2018) 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 state that data must be: 1. Collected lawfully and processed fairly. 4. Data must be accurate and up-to-date. 2. Only used for the reasons specified. Principles of the Data Protection Act (2018) 5. Data must not be stored for longer than necessary, 3. Data must be relevant and not excessive. 6. Data must be stored and processed securely. 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. 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 . However, it is difficult to trace who has stolen work once it has been uploaded to the internet and copies can easily spread, especially television shows and movies. ​ 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. Software Licences A software licence refers to how a user can legally use the software , there are two main types: Open Source Licence Source code is the software code written by programmers . ​ If the software is open source it means that users can view and modify the source code . Linux, Python and Firefox are examples of open source software. Benefits Drawbacks Because the source code is available to edit , it can be customised to the organisation's needs . Often shared in the public domain so users can work together to modify, debug and improve a product. Unwanted features can be removed to make the software run faster . There are security risks - some editors may add malicious code to the program. Open source software is often low in price and sometimes free. It may be difficult to receive support as development is often distributed between people in different locations. The code may be prone to errors as it may not have been tested fully. It requires technical skills to be able to adapt source code efficiently and to maintain the code . Proprietary Licence Another term for a proprietary licence is closed source because the code is restricted - users are prevented from being able to view or modify the source code . You buy the right to use the software but you don't actually own it. Microsoft Office, Fortnite and Spotify are examples of closed source software. Benefits Drawbacks The code is well tested and has been professionally developed. Updates will generally be secure . Users must rely on the company to provide updates and fix issues. This might be infrequent or stop completely. ​ The company can be held to account if it does not perform as listed in the terms and conditions upon purchase. Often not free and may be expensive. Most developers will provide some form of help/support . Users cannot modify, debug or improve the code for their own benefit. Q uesto's Q uestions 6.1b - Legislation: ​ 1a. State the 6 principles of the Data Protection Act (2018) . [ 6 ] 1b. Explain how the Data Protection Act works . In your answer, you should include definitions of a data subject , the data controller and the Data Commissioner . [ 6 ] ​ 2. Describe the 4 principles of the Computer Misuse Act (1990) . [3 ] ​ 3a. What is the purpose of the Copyright, Designs & Patents Act (1988) ? [ 2 ] 3b. Describe 3 actions that CDPA (1988) prohibits . [ 3 ] ​ 4a. Describe the difference between an open source and a proprietary licence . [ 2 ] 4b. State two benefits and two drawbacks of using software with a: ​ Open source licence [ 4 ] Proprietary licence [ 4 ] 6.1a - Impacts of Technology Theory Topics

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 >

1.5 - WWW Technologies Exam Board: OCR Specification: 2016 - Unit 2 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 . ​ There are three types of world wide web technologies : Internet Intranet Extranet The internet i s a global network of interconnected networks . ​ The internet is public and users have open access . ​ ​ Examples of use: Accessing web pages to shop and watch videos . Businesses may use web pages to advertise their products and allow customers to purchase items. An intranet is a private network that is only accessible to authorised users (e.g. members of a business or school). Intranets are private and users have closed access . ​ Examples of use: Because an intranet is a secured online area , schools often use an intranet to log in to that displays information for teachers and students (such as test results or upcoming events ). Businesses might use an intranet for employees to see sales and performance data or for communication because it can be accessed remotely . An extranet is a private network that is accessible using the internet but provides access only to authorised users . ​ Extranets are private and users have shared access . ​ Example of use: Hotel booking companies (like booking.com) use an extranet to allow hotel owners to log in via the internet to access and update their information. Network Characteristics When connecting to WWW technologies there are several characteristics that a user must consider:​ Speed Speed refers to how quickly data can be accessed . For example, an extranet is the slowest network to use because it must be accessed through the internet first. Security Security relates to how likely the data will be kept secure . An intranet is more secure than the internet because only authorised users can log in. Access Levels Access levels , or permissions , refers to who can see what, in terms of data and files . Resources on an intranet can be set so that only certain users can view them. Accessibility This characteristic relates to how available the data is . For example, the internet can be accessed on any network-enabled device, at any time . Q uesto's Q uestions 1.5 - WWW Technologies: ​ 1. Explain the difference between the internet and the world wide web . [2 ] ​ 2. Describe each of the 3 types of WWW technology . You must mention whether they are private or public and what type of access they have. a. Internet b. Intranet c. Extranet [2 each ] ​ 3. Describe at least one example of how each of the 3 types of WWW technology could be used . [6 ] ​ 4. Describe the 3 WWW technologies in terms of each of the 4 network characteristics . You need to think carefully about this; the descriptions under each icon above can help you with certain answers. To start, describe the speed, security, access levels and accessibility of an intranet . [12 each ] 1.4 - Internet Connections Topic List 1.6 - Information Formats

Frequently Asked Questions about Computer Science Newbies Who made CSNewbs? My name is Mr Pulsford . I am from London and I am currently the Head of C omputer Science at a secondary school in South Yorkshire , England . When and why did you make this? I wanted to make a resource that my students could access outside of the classroom . I was working on a paid summer project at G o o g l e in London in 2016 when I was inspired to start the site. I've been updating it ever since as much as I can, outside of lessons and life. I made CSNewbs to support students in lessons and at home because Computer Science can be a tricky subject and many websites are too technical or peripheral . Which courses does CSNewbs cover? The ' GCSE ' section follows the OCR specification ( 2020 ) and Eduqas / WJEC specification ( 2020 ). The ' CTech ' section follows the OCR Cambridge Technicals Level 3 IT 2016 specification for Unit 1 (Fundamentals of IT) and Unit 2 (Global Information). The ' Programming ' section contains material for Python , HTML , Greenfoot and others. The ' KS3 ' section covers basic Computer Science topics aimed at Year 7 - 9 students . ​ Do the exam boards pay you money for this? CSNewbs is not affiliated with any exam board , financially or otherwise . The content on this site has been independently created by closely following the publicly released specifications by Eduqas and OCR. ​ Can I get a level 9 / distinction just from CSNewbs? The content on this website is of high-quality and should be used to guide students towards a better understanding of the course's content. Like all resources however , it should be supported with a range of appropriate material and sound classroom teaching . CSNewbs makes no miraculous claims linking content use and final exam results.​ How did you make this website? CSNewbs.com was created and is maintained using Wix . What's the deal with copyright? CSNewbs is protected by copyright , and copy / paste features have been disabled on the site. All images have either been created by myself or used from Wix's copyright-free vector gallery / their stock image library . Embedded videos are linked to content from the CSNewbs YouTube page. If you think any content on this site infringes a copyright-protected work , please email me, and I will make immediate changes . I don't see any adverts, how are you making money? You're right, there are no adverts and I intend to keep it that way. I don't make and never have made any money from this website. Can you add Unit 3 / OCR A-Level / something else? The site continues to expand over time with new content . The eventual aim is to cover every exam board for GCSE Computer Science but that will take a lot of time! How come something on the site isn't working at my school? Your school's IT administrators may have blocked some elements such as JavaScript or embedded YouTube videos . The videos can be watched directly on YouTube (if not blocked on your school network). Who is the robot? The robot is called Questo . It's the site mascot and it appears on most pages to ask you questions about the content (' Questo's Questions '). It used to have a body but since 2020 it's just a head. I can't believe one person made this whole site while teaching and the rest, what are your long-term plans? If you work for an exam board or educational resource organisation , and your organisation has opportunities available , please send me an email. How can I contact the creator of CSNewbs? The contact email is: Privacy Policy There are social media pages for CSNewbs but with busy times recently they are rarely updated :

Python 12 - Error Handling Errors When an error occurs in Python, you may see a chunk of red text like this. ​ This is very useful when creating programs as it tells us the exact line of the error (10), and its type (NameError). ​ However, a completed program should have code in place for when an unexpected error occurs – we call this exception handling . General Exception In this example, Python will attempt to run the code indented beneath try . If there are no errors then the code will stop just before except . If an error does occur then the Exception code will be run . If we enter a correct value then the program will execute normally: But if an error occurs (such as writing a string when an integer is expected) then the Exception code will run : You can add the else command to your code that will execute only if there are no errors : If a valid number is entered then the else code will be printed: If a code generating an error is entered then the except code will be printed: Practice Task 1 Create a program that asks the user to input their age. ​ Don't forget to use the int command. ​ Use try and except to print a message if a number is not inputted. Example solution: Specific Exceptions The Exception command used in the section above is for any general error that occurs. You can also use specific except commands for a variety of errors. ​ Below is a program with two different specific exception commands for one try statement: If a Value Error occurs, such as when the wrong data type is entered , then related code will be printed: Or if the user tries to divide by zero then a Zero Division Error will be triggered which prints a relevant response: Other types of exception can be found here . Practice Task 2 Create a program that asks the user to input a number and then divides this value by 999. ​ Create a Value Error and Zero Division Error exception and include an appropriate message in both. Example solution for Zero Division: ⬅ 11 - Graphical User Interfac e Extended Task 1 (Pork Pies) ➡

Greenfoot Code Glossary Greenfoot Home This code will work for Version 2.4.2 which is used in Component 2 of the 2016 WJEC/Edquas specification . Key Down 270 if (Greenfoot.isKeyDown("right" )) { setRotation(0); move(1); } 180 90 0 Bounce At Edge if (isAtEdge()) { turn(180); } move(1); if (Greenfoot.getRandomNumber(10)<1) { turn(Greenfoot.getRandomNumber(90) - 45); } Random Remove Object if (isTouching(Apple.class )) { removeTouching(Apple.class ); } Play Sound Greenfoot.playSound("pop.wav" ); Stop Greenfoot.stop(); Counter - (Write this code when an object is removed) Counter counter = (Counter) getWorld().getObjects(Counter.class ).get(0); counter.add(1); Stuck? If you start typing but can't remember what commands come next, press Ctrl and Space together to show a list of all possible commands that you can use.

top Python 1a - Printing Printing in Python To output a message onto the screen, use the print command. Then place your message within brackets and speech marks . For example: print ( "Welcome to Python!" ) When you run the program, the text will print to the Python console: Welcome to Python! Printing Task 1 (Full Name & To Your Left) On the first line, print your first name and surname. ​ On the next line, write another print statement to print t he name of the person (or thing) to your left. Example solution: Elsie Parker pencil case Printing over Several Lines One way of writing across multiple lines is to write several print commands like this: print ( "Welcome to...." ) print ( "Computer Science " ) print ( "Newbies!!! " ) = Welcome to .... Computer Science Newbies!!! However, when we program, we always want to make our code the most efficient it can be by using as few lines as possible . ​ Therefore you can write \n within a printed statement to move it to the next line. ​ Make sure you use \ and not / otherwise it will print the slash and not make a new line! print ( "Welcome to....\n Computer Science\n Newbies!!! " ) = Welcome to .... Computer Science Newbies!!! Both pieces of code display the same thing, but the second one is more efficient because it only uses one line. Printing Task 2 (Name, Colour, Movie) Use \n to write your name, favourite colour and favourite movie in only one line of code. Example solution: Matthew yellow Interstellar ⬅ Setting Up Python 1b - Comments ➡