Learn about protocols including FTP, HTTP, POP, SMTP, SNMP, TCP, UDP, ICMP, IP and the TCP/IP stack. Resources based on Unit F161 (Developing Application Software) for the OCR Cambridge Advanced Nationals in Computing (H029 / H129) AAQ (Alternative Academic Qualification). Qualification: Cambridge Advanced Nationals in Computing (AAQ) Certificate: Computing: Application Development (H029 / H129) Unit: F161: Developing Application Software 3.2 - Protocols Watch on YouTube: Protocols TCP/IP Stack You need to know the role and uses of specific common protocols (FTP , HTTP , POP , SMTP , SNMP , TCP , UDP , ICMP , IP ). You also need to understand the structure , content and use of the 4-layer TCP/IP stack . What You Need to Know Common Protocols A protocol is a set of rules that determines how data is communicated between devices over a network . FTP FTP (File Transfer Protocol ) is used to transfer files between computers over a network , typically between a client and a server . It is used when uploading or downloading files from a server , such as transferring website files to a web server . HTTP HTTP (HyperText Transfer Protocol ) is used to request and transfer webpages and other web content between a web browser and a web server . It is used when accessing websites or when web-based applications communicate with servers . However, HTTPS is the secure , encrypted version commonly used today. POP POP (Post Office Protocol ) is used by an email client to retrieve emails from a mail server , traditionally storing them on the user's device . It is used when emails need to be downloaded from a mail server for access through an email application , particularly where local or offline access is required . SMTP SMTP (Simple Mail Transfer Protocol ) is used to send and transfer email messages between email clients and mail servers and between mail servers . It is required when a user sends an email , including transferring that email between mail servers on its way to the recipient . SNMP SNMP (Simple Network Management Protocol ) allows network administrators and management software to monitor and manage devices on a network to collect information about their status . It is used to monitor devices such as routers , switches , servers and printers , for example checking whether a network device is operating correctly . TCP TCP (Transmission Control Protocol ) provides reliable and ordered delivery of data packets between devices . It checks that packets arrive correctly and retransmits missing packets when necessary. It is used when accuracy and reliability are more important than speed , such as transferring files , loading webpages and sending emails . UDP UDP (User Datagram Protocol ) sends data quickly , although without checking that every piece has arrived or is in the correct order , reducing delays . It is used when speed is more important than perfect delivery , such as live video/audio , online gaming and voice calls . ICMP ICMP (Internet Control Message Protocol ) is used to send network status , diagnostic and error messages between network devices . It is required when diagnosing network problems and checking whether another device can be reached , such as when using the ping command. IP IP (Internet Protocol ) addresses and routes data packets across networks by using IP addresses to uniquely identify devices . It is used when data needs to be sent between devices across networks , with IP helping packets travel from the source towards the correct destination using an appropriate route . TCP/IP Stack The TCP/IP stack is a four-layer model that describes how data is prepared , transmitted across networks and received by applications . When sending data , it travels down through the layers . When receiving data , it travels up through the layers . Different protocols are used at specific layers of the model. Application Layer This is the top layer , where network applications and services interact with the network . It includes protocols such as HTTP , FTP , SMTP , POP and SNMP . It determines how applications communicate and exchange specific types of data across a network . Example : A web browser uses HTTP to request content from a web server . Transport Layer This layer is responsible for transporting data between devices and includes TCP and UDP . It determines how data should be delivered , including whether reliability (using TCP ) or speed (using UDP ) is more important . Example : TCP can ensure that a downloaded file arrives completely and in the correct order , while UDP can prioritise speed during an online game . Internet Layer This layer is responsible for addressing and routing packets between networks and includes protocols such as IP and ICMP . It ensures packets can travel towards the correct destination using IP addresses . Example : IP is used to route packets across the internet to the destination device . Network Access Layer This is the lowest layer , concerned with how data is physically transmitted across the network using technologies such as Ethernet (a wired connection) and WiFi . It handles communication between a device and the network it is directly connected to . Example : A laptop could transmit data wirelessly to a local router using WiFi . Q uesto's Q uestions 3.2 - Protocols: 1. What is a network protocol , and why do you think protocols are needed when devices communicate ? [ 2 ] 2. State the role of FTP , HTTP , POP , SMTP and SNMP and give an example of when each would be used. [2 each ] 3. State the role of TCP , UDP , ICMP and IP and give an example of when each would be used. [2 each ] 4. Describe the structure and purpose of each of the four layers of the TCP/IP stack . [2 each ] 5. Explain how different protocols and layers of the TCP/IP stack can work together to transfer data across a network , such as sending an email on a wired connection . [ 4 ] Online games use UDP because receiving data quickly is often more important than receiving every single packet . A tiny amount of missing data may be preferable to the game pausing while it waits for it to be resent . D id Y ou K now? 3.1 - APIs Topic List 4.1 - Security Considerations

Learn about the eight rules of Boolean algebra expressions. Based on the 2020 Eduqas (WJEC) GCSE specification. 2.2: Boolean Algebra Exam Board: Eduqas Specification: 2020 Boolean algebra is used to simplify Boolean expressions so that they are easier to understand. Because calculations can use dozens of logical operators, they are simplified in Boolean Algebra using symbols rather than words. Take your time and don't panic. In an exam, you might get a list of identities (rules) to use. One tip to solving boolean algebra is to imagine that A and B are real expressions . In the examples on this page, imagine: A represents the true statement 'the sky is blue' B represents the true statement 'grass is green' 0 always means FALSE 1 always means TRUE Boolean Symbols A = NOT A A . B = A AND B A + B = A OR B Boolean Identities are the rules that are used to simplify Boolean expressions. Each identity (law) has an AND form and an OR form , depending on whether AND or OR is being used . Commutative Law AND form: OR form: This law just switches the order of the expressions . For example, 'sky is blue' AND 'grass is green' makes logical sense in either order. Idempotent Law = AND form: OR form: This law removes repetition . Complement Law NOT AND form: The sky cannot be blue and not blue at the same time, so it must be 0 (FALSE). OR form: The sky is blue or not blue must be 1 (TRUE) as it has to be one of these options. Identity Law AND form: 1 represents TRUE . Both statements are true so it can be simplified as just A . OR form: 0 represents FALSE . Because A is true, you can ignore the false statement and it can be simplified as just A . Annulment Law AND form: 0 represents FALSE . Even though A is true, a statement cannot be true and false at the same time, so it must be 0 (FALSE). OR form: 1 represents TRUE . Both statements are true so this can be simplified as just 1 (TRUE). Absorption Law AND form: OR form: Absorption law reduces a bracket into one value. If the first A is true then both values in the brackets are true but if the first A is false then both values are false. Therefore this equation relies entirely on A and can be simplified as just A . Association Law ( ) AND form: OR form: This law separates a bracketed expression that uses the same operator inside and outside the brackets by removing the brackets . Distribution Law ( ) = ( ) ( ) AND form: OR form: The value outside of the bracket (e.g. A) is multiplied by both values inside the brackets , forming two new brackets which are linked by the logical operator formerly within the bracket . Notice that the logical operator role is switched , e.g. AND switches from within the brackets, to between the new brackets. A note about distribution law - The three values may not necessarily be three separate letters (e.g. A, B and C) as B or C could be NOT A for example. A NOT value is considered a new value , e.g. A and Ā are separate values. Another note about distribution law - Exam questions may ask you to perform the distribution law (or any law) in reverse . For example, converting (A+B) . (A+C) into A + (B.C) Boolean Algebra Exam Question Some previous exam questions have listed helpful laws for you but others haven't, so you should know each individual law . In a previous exam, the candidates were given three general laws to help them . P, Q and R just represent three different values. P . 1 = P (Identity Law) P . Q + P . R = P. (Q + R) (Distribution Law) P + P = 1 (Complement Law) Using the rules above , candidates were asked to simplify the following expression : X = A . B + A . B The general laws have been give n to you for a reason. You need to look at the laws provided and see which one currently matches the expression in front of you . If you look closely in this example, the second law is very similar to the expression you are asked to simplify so you can use it to make the first simplification, just swap P for A, Q for B and R for NOT B: Using this law P . Q + P . R = P. (Q + R) X = A . B + A . B simplifies as: X = A . (B + B) Now you need to see which of the three provided laws can be used with the current expression . The third law is very similar to the expression you now need to simplify further , just swap P for B and NOT P for NOT B: Using this law P + P = 1 X = A . (B + B) simplifies as: X = A . (1) And finally, there is one law left to use. The first law is very similar to the expression you now need to simplify further , just swap P for A. Using this law P . 1 = P X = A . (1) simplifies as: X = A You have now used all three laws and the expression is fully simplified . Remember - Look at the laws that you have been given and see which law matches your expression . Q uesto's Q uestions 2.2 - Boolean Algebra: 1. Draw the example equations and write a brief description of each of the eight Boolean laws : Commutative Law Idempotent Law Complement Law Identity Law Annulment Law Absorption Law Associate Law Distributive Law 2. Below are three Boolean identities: P . P = 0 (P + Q) . R = (P . R) + (Q . R) P + 0 = P Using the three rules above , simplify the following expression: X = (A + B) . Ā This law is called ' Inverse Law ' in the Eduqas 2016 teacher guidance but ' Complement Law ' in the 2020 specification. This law is called ' Zero and One Law ' in the Eduqas 2016 teacher guidance but ' Annulment Law ' in the 2020 specification. This law is called ' Associate Law ' in the Eduqas 2016 teacher guidance but ' Association Law ' in the 2020 specification. This law is called ' Distributive Law ' in the Eduqas 2016 teacher guidance but ' Distribution Law ' in the 2020 specification. 2.1 - Logical Operators Theory Topics 3.1 - Network Characteristics

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 elements of a data flow diagram and factors that may disrupt them. Based on the 2016 OCR Cambridge Technicals Level 3 IT specification for Unit 2 (Global Information). 5.2 - Data Flow Diagrams Exam Board: OCR Specification: 2016 - Unit 2 A data flow diagram is a visual representation of how data is transferred within a system or organisation . Data flow diagrams are often abbreviated to just 'DFD '. You will need to recognise the symbols , understand the diagrams and explain how data flow can be affected . Data Flow Diagram Symbols The common symbols used in a DFD are shown below: External Entity (e.g. Employee, Customer) Alternative DFD symbols you may see on the exam paper (both sets of symbols have been accepted in previous exam papers): Process (e.g. Calculate Pay, Review Application) Data Store (e.g. Staff Database, Customer Database) External Entity Process Data Store Data Flow Level 0 data flow diagrams show the transfer of data in a simple manner . Processes may be generalised and not shown separately , for a more basic overview . Below is an example of a Level 0 DFD to show the process of an employee submitting an application to be promoted : Level 1 data flow diagrams show the transfer of data in a more detailed manner . Processes are shown separately , for a more complex and realistic overview . Below is an example of a Level 1 DFD to show the process of an employee submitting an application to be promoted . The individual processes have been expanded from the Level 0 DFD above to show how the application must first be signed off by an administrator before it is reviewed by management: Rules for Drawing a Level 1 DFD Data flows only in one direction . Every data flow is labelled (with the data itself , not the action). Every data flow connects to at least one process . At least one input or output for each external entity . Impacts Affecting the Flow of Information There are several reasons why the flow of information within an organisation may be delayed or inefficient , such as: Information characteristics e.g. information is entered incorrectly, causing delays. Human error e.g. information is lost or staff don't follow protocol. Hardware failure e.g. network connection breaking or system failure. Communication breakdown e.g. meetings postponed or emails unread. Q uesto's Q uestions 5.2 - Data Flow Diagrams: 1. Draw the symbols for the four parts of a data flow diagram . [4 ] 2. Look at the image of the Level 1 DFD . State one example of: An external entity A process A data flow A data store [1 each ] 3. Give one difference between a Level 0 and Level 1 DFD . [2 ] 4. State three rules for drawing a correct data flow diagram . [3 ] 5. After heavy snow, a school has decided to shut for the next two days. Many parents were not informed of this decision and are angry that they brought their children in. Give three reasons why the transfer of data (the data being a message about school closure) might not have flowed efficiently in this example. [6 ] 1 Level 0 Data Flow Diagram Level 1 Data Flow Diagram 5.1 - Data Types & Sources Topic List 6.1 - Security Principles

Learn about the three types of translators - assemblers, interpreters and compilers. Also, understand the differences between compilers and interpreters. Based on the 2020 Eduqas (WJEC) GCSE specification. 10.1: Translators Exam Board: Eduqas Specification: 2020 What is a translator? A translator changes (translates) a program written in one language into another language (usually machine code ). There are three types of translator : Assembler An assembler converts low level assembly language into machine code . INP STA 33 INP STA 34 LDA 33 ADD OUT HLT Interpreter An interpreter converts high-level language one line at a time into machine code and executes it. PYT HON Compiler A compiler converts high-level language into machine code for execution at a later time. The entire program is converted at once . PYT HON 0010 1011 0101 0101 0110 0111 0101 0001 0101 0101 0010 1011 0101 0101 0110 0111 0101 0001 0101 0101 0010 1011 0101 0101 0110 0111 0101 0001 0101 0101 Differences between an interpreter and a Compiler: Interpreter Compiler Execution Method: An interpreter translates source code (high level code) into machine code one line at a time . Execution Speed: An interpreter is slower than a compiler because the code must be reinterpreted each time the program is run. Complexity: Interpreters are smaller, simpler programs . Error Reporting: In error reporting, the interpreter would encounter the errors and report it to the user immediately and stops the program from running. Repetition: Interpreted programs can be edited and run without translating the whole program . Interpreters must reinterpret the program every time it is run. Execution Method: A compiler translates all the source code (high level code) into machine code in one go . A compiler produces an executable file that will run on other machines without the compiler needing to be installed. Execution Speed: Compilers can produce much more efficient code than interpreters making the compiled programs run faster . Complexity: Compilers tend to be large complex programs . Error Reporting: The compiler would analyse the entire program , taking note of where errors have occurred and record them in an error file . Repetition: Compilation requires analysis and the generation of the code only once , whereas interpreters must re-interpret each time. However, compiled programs have to be re-compiled after any changes have been made. x1 ∞ x1 Q uesto's Q uestions 10.1 - Translators: 1. Briefly describe each type of translator : a. Assembler [ 1 ] b. Interpreter [ 2 ] c. Compiler [ 2 ] 2. Compare interpreters and compilers for each of the following features : a. Execution Method b. Execution Speed c. Complexity d. Error Reporting e. Repetition [ 10 total ] 9.1 - IDE Tools Theory Topics 10.2 - Stages of Compilation

The list of topics in the 2020 OCR GCSE Computer Science specifications. OCR GCSE Computer Science These pages are based on the J277 GCSE Computer Science specification from the Cambridge OCR exam board. Component One: Computer Systems OCR GCSE Key Term Generator Paper 1 Playlist on YouTube 1. Systems Architecture 1.1a - The CPU 1.1b - The Fetch-Execute Cycle 1.2 - CPU Performance 1.3 - Embedded Systems 2. Memory & Storage 2.1 - Primary Storage (Memory) 2.2 - Secondary Storage 2.3 - Units 2.4a - Number Systems 2.4b - Binary Addition & Shifts 2.4c - Character Storage 2.4d - Image Storage 2.4e - Sound Storage 2.5 - Compression 3. Networks 3.1a - Network Types & Performance 3.1b - Network Hardware & Internet 3.2a - Wired & Wireless networks 3.2b - Protocols & Layers 4. Network Security 4.1 - Network Threats 4.2 - Preventing Vulnerabilities 5. Systems Software 5.1 - Operating Systems 5.2 - Utility Software 6. Impacts 6.1a - Impacts of Technology 6.1b - Legislation Component Two: Computational Thinking, Algorithms and Programming Paper 2 Playlist on YouTube 1. Algorithms 1.1 - Computational Thinking 1.2 - Designing Algorithms 1.3 - Searching & Sorting Algorithms 2. Programming Fundamentals 2.1 - Programming Fundamentals 2.2 - Data Types 2.3 - Additional Programming Techniques 3. Producing Robust Programs 3.1 - Defensive Design 3.2 - Testing 4. Boolean Logic 4.1 - Boolean Logic 5. Languages & IDEs 5.1 - Languages & Translators 5.2 - Integrated Development Environment

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 2 Lottery 17 8 4 13 20 Create a program to simulate a lottery draw. First, create an appropriate print line to welcome the user to your lottery draw. Then let the user enter five numbers between 1 and 20. Next, randomise five numbers between 1 and 20. Check to see how many numbers match and output an appropriate response for each scenario (e.g. “You have not matched any numbers, better luck next time!”) Once you have made the base program implement subroutines and lists . Make it as efficient as possible and professional-looking. Use pauses to reveal each number one at a time like a real lottery draw to build suspense. 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: Inputting Numbers Random Numbers Logical Operators Subroutines ⬅ Extended Task 1 (Pork Pies) Extended Task 3 (Blackjack) ➡

Learn about HTML, CSS, JavaScript, search engine indexing, the PageRank algorithm and client-side and server-side processing. Based on the OCR H446 Computer Science A-Level specification. Exam Board: OCR A-Level 3.4 - Web Technologies Specification: Computer Science H446 Watch on YouTube : HTML CSS JavaScript Search engine indexing PageRank algorithm Server-Side & Client-Side Processing This topic looks at the languages that web pages are comprised of (HTML , CSS and JavaScript ) as well as search engines and network processing (client-side and server-side ). HTML HTML ( HyperText Markup Language ) is the standard language used to create and structure web pages . It uses tags enclosed in angle brackets to define elements on a page . A web page begins with , which contains a section for metadata , links and the

Learn about ways to measure the success of protection. Based on the 2016 OCR Cambridge Technicals Level 3 IT specification for Unit 2 (Global Information). 6.4 - Protection Measures Exam Board: OCR Specification: 2016 - Unit 2 Staff Responsibilities It is the staff of an organisation that will spend the most time handling and amending data so the company must have sufficient and effective protection measures in place so that staff are confident in their role and know their responsibilities of information security. Certain staff members may be responsible for types of data within an organisation, such as personal and confidential data. Clearly assigning specific people to roles ensures that they know what their job is and that they are responsible if data is lost. Organisations also need to carefully consider which members of staff have access rights to certain information. If data is sensitive or confidential then the more people that have access to that data , the higher the risk of it being lost or tampered with (accidentally or on purpose). Sensitive data should only be handled and accessed by those who need to use it as part of their job role to limit the chance of data loss. Staff should be trained so that they know how to adequately handle information including basic data security techniques and how to protect data from unauthorised access and loss. Disaster & Recovery Planning With important data often stored on a computer network, it is absolutely vital that a detailed and effective disaster recovery policy is in place in the event of data being lost due to an unexpected disaster. Disasters include natural disasters (e.g. fire, flood, lightning), hardware failure (e.g. power supply unit failing), software failure (e.g. virus damage) and malicious damage (e.g. hacking). There are three clear parts to a disaster recovery policy: Before the disaster: All of the possible risks should be analysed to spot if there are any weaknesses in preparation. Preventative measures should be taken after the analysis, such as making rooms flood-proof or storing important data at a different location . Staff training should take place to inform employees what should happen in the event of a disaster. During the disaster: The staff response is very important – employees should follow their training and ensure that data is protected and appropriate measures are put in place. Contingency plans should be implemented while the disaster is taking place, such as uploading recent data to cloud storage or securing backups in a safe room and using alternative equipment until the disaster is over. After the disaster: Recovery measures should be followed, such as using backups to repopulate computer systems. Replacement hardware needs to be purchased for equipment that is corrupted or destroyed. Software needs to be reinstalled on the new hardware. Disaster recovery policies should also be updated and improved . Assessment and Effectiveness Organisations should conduct information security risk assessments periodically to ensure that their physical and logical measures are up-to-date and that they provide the most effective methods of protection. There may be training drills of what should happen if a disaster or substantial data loss occurs so that the company is prepared . By testing the security measures in place, they can identify any weak-points and fix those highlighted vulnerabilities to minimise the possibility of external and internal data intrusion. As part of an organisation's security assessment, they may identify specific cost impacts . These are necessary financial expenditures to ensure the security of data and systems, such as: Software - e.g. security software such as firewalls may be purchased to protect networked systems. Hardware - e.g. buying secure storage devices and new computer systems. Training - e.g. hiring industry experts to train staff on how to keep data secure. Security - e.g. hiring staff to protect server rooms. Q uesto's Q uestions 6.4 - Protection Measures: 1. Describe why staff are so important when it comes to data protection . [3 ] 2. Explain the steps an organisation should take as part of a disaster recovery plan . Split your answer into before, during and after the disaster. [12 ] 3. Why is it important to conduct information security risk assessments ? [2 ] 4. Describe two cost impacts to a bank of keeping customer data secure. [4 ] 6.3 - Impacts Topic List 6.5 - Physical Protection

Learn about algorithms including pseudocode and flowcharts. Based on the 2020 Eduqas (WJEC) GCSE specification. 8.2: Understanding Algorithms Exam Board: Eduqas Specification: 2020 What is an algorithm? An algorithm is a set of instructions , presented in a logical sequence . In an exam you may be asked to read and understand an algorithm that has been written. To prove your understanding you may be asked to respond by actions such as listing the outputs of the algorithm, correcting errors or identifying an error within it. Programmers create algorithm designs as a method of planning a program before writing any code. This helps them to consider the potential problems of the program and makes it easier to start creating source code. There are two main methods of defining algorithms : Defining Algorithms - Pseudocode & Flowcharts Pseudocode Pseudocode is not a specific programming language but a more general method of describing instructions . It should be unambiguous, and it should not resemble any particular kind of programming language (e.g. Python or Java), so it can theoretically be turned into working code in any language. Generally, pseudocode can be written in any way that is readable and clearly shows its purpose. However, the Eduqas exam board advises that pseudocode for the programming exam should follow the conventions below : Annotation { Write your comment in curly brackets} Define data type price is integer firstname is string Declare a variable's value set price = 100 set firstname = "Marcella" Input / output output "Please enter your first name" input firstname Selection (must have indentation) if firstname = "Steven" then output "Hello" + firstname elif firstname = "Steve" then output "Please use full name" else output "Who are you?" end if Iteration (while loop) while firstname ! = "Steven" output "Guess my name." input firstname repeat Iteration (for loop) for i in range 10 input item next i Define a subroutine Declare Sub1 [Subroutine content indented] End Sub1 Call a subroutine call Sub1 Flowcharts A flowchart can be used to visually represent an algorithm. The flowchart symbols are: Algorithm Examples Below are two different methods for representing the same algorithm - a program to encourage people to buy items cheaply at a supermarket. The program allows the price of items in a supermarket to be entered until the total reaches 100. The total price and the number of items entered are tracked as the program loops. Once the total reaches 100 or more, an if statement checks how many items have been entered and a different message is printed if there are 20 or more items, 30 or more items or less than 20 items. Pseudocode Flowchart {This is a program to see how many items you can buy in a supermarket before you spend over £100} total is integer, itemsentered is integer, itemprice is integer set total = 0 set itemsentered = 0 while total < 100 output "enter the price of the next item" input itemprice total = total + itemprice itemsentered = itemsentered + 1 repeat if itemsentered >= 20 then output "You are on your way to saving money." elif itemsentered => 30 then output "You're a real money saver." else output "Look for better deals next time." end if Reading Algorithms In an exam you may be asked to read an algorithm and prove your understanding , most commonly by listing the outputs . Start from the first line and follow the program line by line , recording the value of variables as you go . When you encounter a for loop , repeat the indented code as many times as stated in the range . Example Algorithm: Start NewProgram i is integer maxvalue is integer input maxvalue for i = 1 to maxvalue output (i * i) ??????? output 'program finished' End NewProgram Example Questions: 1. List the outputs produced by the algorithm if the 'maxvalue' input is 5 . 2. State the code that has been replaced by '???????' and what the code's purpose is. Example Answers: 1. Outputs: 1 4 9 16 25 program finished 2. Missing Code: next i Purpose: Moves the loop to the next iteration. Watch on YouTube Q uesto's Q uestions 8.2 - Understanding Algorithms: 1a. Read the algorithm shown on the left and list all outputs in the correct order if the inputs are 2 for height and 72 for weight . 1b. Give the code that is missing from line 25 . 8.1 - Programming Principles Theory Topics 8.3 - Writing Algorithms

Learn about how to perform binary addition and binary subtraction. Based on the 2020 Eduqas (WJEC) GCSE specification. 4.3: Binary Calculations Exam Board: Eduqas Specification: 2020 What are binary calculations? Binary addition and binary subtraction are methods of adding or subtracting binary values without having to convert them into denary. How to add binary numbers: How to subtract binary numbers: Overflow & Underflow Errors Overflow and underflow errors occur when there is not enough space to accurately represent a binary number in the bits available . What is an overflow error? An overflow error occurs when a binary value is too large to be stored in the bits available . In technical terms, an overflow error occurs if a carry (remainder) is present on the most significant bit (MSB ). The CPU then sets the overflow flag to true . The most significant bit (MSB ) is the largest bit (always the one furthest to the left ) of a binary value (e.g. 128 for an 8 bit value). A flag is an alert signal . It is either on or off. The overflow flag is turned on by the CPU when an overflow occurs. What is an underflow error? An underflow error occurs when a number is too small to be stored in the bits available . The value is too close to 0 to be accurately represented in binary. Q uesto's Q uestions 4.3 - Binary Calculations: 1a. Describe the terms ' most significant bit ' and ' flag '. [ 2 ] 1b. Using the terms from 1a , explain what an overflow error is. [ 2 ] 1c. Describe what is meant by an underflow error . [ 2 ] 2. Add together the following binary values. If an overflow error occurs you must state one has occurred. a. 010110012 and 010001012 [2 ] b. 110110112 and 010111012 [2 ] c. 001101102 and 011010112 [2 ] d. 110110112 and 010101112 [2 ] e. 011011012 and 110101102 [2 ] 3. Subtract the following binary values; put the first value on top of the second value: a. 100110102 and 000110002 [2 ] b. 110110112 and 010111012 [2 ] c. 011101102 and 011010112 [2 ] d. 110110112 and 010101112 [2 ] e. 111011012 and 110101102 [2 ] Watch on YouTube Watch on YouTube 4.2 Signed Binary Theory Topics 4.4 - Arithmetic Shift

Consider multiple extensions to increase the complexity of your Greenfoot game. Part 7 of the Greenfoot Tutorial for the Eduqas / WJEC GCSE 2016 specification. 7. Extension Ideas Greenfoot Tutorial This concludes the tutorial for a simple Greenfoot game! Try a combination of the suggestions below to add complexity to your game: 1. Make a New Class for 'Bad' Collectibles Create a new subclass in the Actor classes section for a new collectible that will lower the score if picked up. Add code to your main character to remove the collectible when they touch . Add code to decrease the counter by 1 at the same time. 2. Make the Collectibles Move Randomly Copy the code from your enemy class that makes it move randomly and bounce on edge , and paste this into your collectible class . This makes it harder to catch the collectables, especially if there are 'bad' objects to avoid. 3. Stop the Game Go to the code of your enemy and add the line underlined in red within your removal code. This will stop the game if your main character is eaten. 4. Make the Game Multiplayer Create a new subclass in the Actor classes section for a new main character that will be controlled by a second player . Add code to your new character to move it right, down, left and up . Choose different keys for each direction , such as the WASD keys or IJKL keys. If the second player touches a collectible , add code to decrease the score . Multiplayer Rules: Player 1 wins if the final score is above 0 . Player 2 wins if the final score is negative . It is a draw if it finishes on 0 . < Part 6 - The Counter