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A list of programming topics including HTML, Greenfoot, Python. All Programming Topics Python HTML Greenfoot Assembly Language App Inventor 2

Learn about applications, utility software, open source and closed source, translators including interpreters, compilers and assemblers, stages of compilation (lexical analysis, syntax analysis, code generation and optimisation) and linkers, loaders and libraries. Based on the OCR H446 Computer Science A-Level specification. Exam Board: OCR A-Level 2.2 - Applications Generation Specification: Computer Science H446 Watch on YouTube : Application software Utilities Open & closed source High & low level language Translators Stages of compilation Linkers, loaders & libraries This topic explores key types of software and how they support computer systems and users . It explains different kinds of applications , utilities , translators and compares open and closed source software . Another important concept is compilation , with knowledge required of its different stages , as well as linkers , loaders and software libraries . Applications Software Applications software allows users to carry out productive or creative activities such as document editing , data analysis , communication or media creation . Common examples include word processors (e.g. Microsoft Word or Google Docs ), spreadsheets (e.g. Excel or Sheets ), database management systems (e.g. Access ), web browsers (e.g. Chrome or Safari ) and graphics editors (e.g. Photoshop ). Applications can be general-purpose , serving many uses , or special-purpose , created for a specific function like payroll or medical record management . Utilities Utility software is system software designed to maintain , optimise and manage a computer’s performance , often running in the background to support the operating system . Examples include security tools like an antivirus , backup , compressors , disk management utilities and defragmenters . Defragmentation is the process of reorganising files on a hard drive so that parts of each file are stored together in contiguous blocks , improving access speed . Open Source & Closed Source Open source software has its source code (the actual code written by its developers ) made publicly available , allowing users to view , modify and share it freely . An open source licence encourages collaboration , transparency and community-driven improvement . However, it may lack official technical support or guaranteed updates . Closed source software has its source code private , restricting modification and redistribution . It is usually sold commercially with paid licences , regular updates and dedicated technical support . Bug fixes and quality assurance are out of the user's control , being managed by the developer . Support may end without warning . High & Low Level Languages Programming languages can be split into high-level and low-level , based on how close they are to the computer’s hardware . High-level languages are easier to read and write , while low-level languages give direct control over hardware but are harder to use . High-level languages like Python or Java are similar to natural human language, making them easy to write , understand, and debug . Low-level languages include machine code (binary ) and assembly language but are written for specific processor architecture . Translators Translators are programs that convert source code written in one programming language into another form that the computer's CPU can understand - typically machine code (binary ). An assembler translates assembly language into machine code that the CPU can execute directly . An interpreter translates and executes high-level code in a line-by-line method, stopping when an error occurs . A compiler translates the entire high-level program into machine code before execution , producing an executable file . Stages of Compilation Compilation is a complicated process to convert high-level program code into machine code . It consists of four key stages : Lexical analysis breaks the source code into tokens , such as keywords , identifiers and operators . Spaces and comments are removed and a symbol table of identifiers is created. Syntax analysis checks that the token sequence follows the grammatical rules of the programming language , building an abstract syntax tree . Code generation converts the abstract syntax tree into object code (unfinished machine code ) the CPU can understand . Code optimisation improves the efficiency of the generated code , for example by reducing redundant instructions or improving execution speed . Libraries, Linkers & Loaders Compilation also requires additional programs, such as a linker and loader and the use of libraries . A library is a collection of pre-written code created by other programmers that contains useful routines and functions which can be reused in a program. A linker combines object code and libraries , resolving references so that a final executable file can be created . A loader copies an executable file from secondary storage into RAM , ready for execution by the processor . Q uesto's K ey T erms Applications: database, word processor, web browser, graphics manipulation, spreadsheet software, presentation software Utilities: defragmentation, system cleanup, file manager, device driver, security tools Open & Closed Source: source code, open source, closed source Translators: assembler, interpreter, compiler, machine code Stages of Compilation: lexical analysis, token, syntax analysis, abstract syntax tree, code generation, code optimisation, library, linker, static linking, dynamic linking, loader D id Y ou K now? Grace Hopper , a US Navy rear admiral , is credited with creating one of the first compilers in 1952 and coining the term ' compiler '. She also helped develop the languages FLOW-MATIC and later COBOL , which is still used today . 2.1 - Systems Software A-Level Topics 2.3 Software Development

Learn about two methods of representing negative numbers in binary - sign and magnitude and two's complement. Based on the 2020 Eduqas (WJEC) GCSE specification. 4.2: Signed Binary Exam Board: Eduqas Specification: 2020 What are Sign and Magnitude and Two's Complement? Sign and Magnitude and Two's Complement are both methods of writing positive and negative binary values . Sign and Magnitude is simpler but will cause incorrect answers if used in binary calculations . Two's Complement is more complex but will generate correct answers when used in binary calculations . Sign & Magnitude The most significant bit (MSB ) is the largest bit of a binary number - the one furthest to the left . The MSB is the sign - it represents whether the binary value is positive or negative . If the sign is 0 then the binary number is positive . If the sign is 1 then the binary number is negative . The other bits represent the magnitude - the value of the binary number. For an 8-bit binary number , the range is -127 to 127 , because only 7 bits are used to define the magnitude. Sign & Magnitude: Problems Sign and magnitude is not commonly used by computers for two main reasons: Performing binary addition and subtraction (see section 4.3 ) will often cause a wrong result . In the example below, -7 + 3 should equal -4 but the result given is 2. + Sign and magnitude creates two different values for 0 - positive 0 and negative 0 which is incorrect. Two's Complement Two's complement is a method of representing positive and negative binary values. It is used often by computers because binary calculations will work correctly and there is only one value for zero. Two's Complement: Denary to Binary To represent a negative value using two's complement follow these steps: Write out the positive value in binary . Start on the right-hand side and move along, copy all 0s until you get to the first 1 . The first 1 is copied too. After the first 1 invert each value (change to its opposite ). So 0 becomes 1 and 1 becomes 0 . 1. 2. 3. Two's Complement: Binary to Denary To convert a binary number to denary using two's complement you must remember that the MSB is a negative value . Just add the numbers with 1 together to work out the denary value . Q uesto's Q uestions 4.2 - Signed Binary: Sign & Magnitude 1. Using sign and magnitude , convert the following values to denary : a. 00011101 b. 11100011 c. 10110110 d. 01001111 [1 each ] 2. Using sign and magnitude , convert the following values to binary : a. 83 b. -13 c. -102 d. -24 [1 each ] 3. Describe two problems when using sign and magnitude . [ 4 ] 4. Using sign and magnitude , the range of numbers that can be represented in 6 bits is from - 31 to + 31 . State the range of numbers that can be represented using sign and magnitude in the following bits: a. 8 bits b. 4 bits [1 each ] Two's Complement 1. Using two's complement , convert the following values to binary : a. -20 b. -49 c. -87 d. -113 [2 each ] 2. Using two's complement , convert the following values to denary : a. 10110010 b. 11101110 c. 01101011 d. 10011111 [2 each ] Watch the video to learn how sign and magnitude is used to represent negative numbers in binary . Watch the video to learn how two's complement is used to represent negative numbers in binary . Watch on YouTube Watch on YouTube 4.1 - Number Systems Theory Topics 4.3 - Binary Calculations

Learn about the five main roles of an operating system including CPU management, security, managing processes and the user interface. Based on the J277 OCR GCSE Computer Science specification (first taught from 2020 onwards). 5.1: Operating Systems Exam Board: OCR Specification: J277 Watch on YouTube : Operating Systems What is an Operating System? An operating system (OS ) is software that helps to manage the resources of a computer system and provide the interface between the user and the computer’s hardware . There are five main functions of an operating system: Memory Management & Multitasking All programs must be temporarily stored in RAM for the CPU to be able to process them. The OS transfers programs in and out of memory from the hard drive (or virtual memory ) when processing is required - programs are removed from RAM when closed to free up space for other tasks. The operating system can only perform one process at a time , but through memory management it can appear that more than one process is being executed - this is called multitasking . Peripherals Management & Drivers A peripheral is an external device connected to a computer system to input or output data . Data is transferred between external devices and the processor and this process needs to be managed by the operating system . A device driver is a program that provides an interface for the OS to interact and communicate with an external device . Drivers are hardware dependent and OS-specific . The driver translates the OS’ instructions into a format the specific hardware can understand . Because the CPU and the peripheral will process data at different speeds , a buffer is typically used to temporarily store data until it can be processed . User Management The OS allows users to create , manage and delete individual accounts . User accounts can be granted different access rights such as an administrator or guest . The OS will manage security settings such as allowing passwords to be reset and can also be used to monitor login activity . File Management The operating system creates and maintains a logical management system to organise files and directories (folders ). File management allows files to be named , renamed , opened , copied , moved , saved , searched for , sorted and deleted . It also allows users to set access rights for specific files and to view file properties . User Interface The final function of an operating system is to provide a user interface , allowing a human to interact with the computer system . The way in which a user can navigate a computer system is known as human-computer interaction ( HCI ). Graphical User Interface (GUI) The most common type of user interface is a graphical user interface (GUI ) which can be presented in the following ways: Icons are displayed to represent shortcuts to applications and files. Multiple windows can be opened at the same time and switched between. A folder and file system is displayed and manipulated allowing for copying , searching , sorting and deleting data. The interface can be customised , such as changing font sizes and the desktop background . The taskbar allows shortcuts to be pinned for quick access . Menus can be opened from the Start button to display files and shortcuts. System settings can be accessed such as network and hardware options . Command-Line Interface Other types of user interface do exist, such as a command-line interface (CLI ). This type of interface is entirely text-based and requires users to interact with the system by typing commands . This is a complicated process and mistakes could easily accidentally delete data. There are many commands to learn so only experts who have been trained t o learn this interface will be able to efficiently make use of it. Other Interfaces Humans can interact with computers using other types of interface , such as: Touch-sensitive interface (e.g. smartphones ). Voice-sensitive interface (e.g. smart speakers ). Menu-driven interface (e.g. ATMs in banks). Q uesto's Q uestions 5.1 - Operating Systems: 1. Describe each role of the operating system : Providing a user interface [ 3 ] Memory management (and multitasking) [ 3 ] Peripheral management (and drivers) [ 3 ] User management [ 3 ] File management [ 3 ] 2. Describe 5 different ways the operating system can provide a graphical user interface (GUI) . [5 ] 4.2 - Preventing Vulnerabilities Theory Topics 5.2 - Utility Software

Learn about the responsibilities of job roles such as an application designer, mobile application designer, project manager, systems analyst, systems designer, user experience designer (UXD) and user interface designer (UID). 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) 6.1 - Job Roles Watch on YouTube : Job roles Developing a new application is rarely a solo project and often involves a team working together . There are seven specific job roles for application development you need to know, from application designer to user interface designer (UID ). For each job role , you must understand its main responsibilities and how it contributes to software application development . Job Roles Application Designer Application designers create the blueprint that guides developers , ensuring the software performs required tasks efficiently and logically . They design the structure and layout of software applications . Mobile Application Designer Mobile application designers ensure the software is suitable and user-friendly on mobile devices . They design apps specifically for mobile platforms (e.g. iOS or Android ) with touch-semsitive interfaces and responsive design . Project Manager Project managers keep the project organised , on track and within budget , making sure all team members work efficiently towards the same goals . They must be organised to effectively plan and oversee the entire software development process . Systems Analyst Systems analysts ensure the final software solves the right problems by fully understanding what users and businesses actually need . They gather and analyse user requirements and identify possible improvements or new system solutions . Systems Designer Systems designers provide the technical structure of the system , ensuring it functions correctly and efficiently under real-world use . They translate requirements into detailed system designs and specify data structures . User Experience Designer (UXD) UXDs ensure the software is pleasant and efficient to use, increasing user satisfaction and reducing errors or frustration . They focus on how users interact with the application and research user behaviour through testing and feedback . User Interface Designer (UID) UIDs make the application visually appealing and easy to navigate , supporting a good first impression and smooth interaction . They design the visual elements including the style of buttons , menus , icons and overall layout . Q uesto's Q uestions 6.1 - Job Roles: 1. Explain how UXDs and UIDs can work together to design applications . [5 ] 2. Describe how systems analysts contribute to application development . [4 ] 3. Describe the responsibilities of two other roles not mentioned in Q1 or Q2 . [ 6 ] There were estimates of about 6,000 developers working together across Rockstar's global video game studios to make Grand Theft Auto VI . D id Y ou K now? 5.3 - HCI Designs & Diagrams Topic List 6.2 - Communication Skills

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 6 'Guess the Word' Game Create a Python program similar to the hit New York Times puzzle game Wordle . Allow the user to make guesses to match the randomly chosen hidden word , stopping when they get it correct. You can download a list of 5-letter words on this page. You will need to read in each line of the list and randomly select one - don’t forget to import the random library . Check if each letter of the user’s inputted word is in the randomly selected word . If you are using an IDE like Replit you can use the colorama library and the Fore command to turn the text: Green if the letter is in the correct position . Red if the letter is not in the selected word . Yellow if the letter is in the selected word but not in the correct position . Add your own flair and additional features to your program as an extension, including limiting the number of guesses and recording how many attempts it took to get the correct answer. Download a file of 534 5-letter words: 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 a while loop to repeatedly allows the user to enter words until they match the correct word. Section 10 will help you to open, write and r ead from files . Download the file of 5-letter words from the link above. You will need to randomly select a word from the file. The choice command will help. Selection will be necessary to check if each letter in the inputted word matches the letter in the same position in the correct word. String handling is needed to select specific letters in a string. You will need to use .rstrip() on the selected line (word) that you have randomly chosen from the file. This removes any hidden characters that may interfere with checking if it is equal to the inputted word. 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: The word the user enters should be checked , letter by letter , against the letters in the same position in the randomly chosen correct word . Remember that the first letter in a word has the position 0 , not 1. Below is an example of some incomplete code you may wish to use in your solution. ⬅ Extended Task 5 (Colour Collection) Extended Task 7 (Number Game) ➡

Learn about key mnemonics used in assembly language and how very simple programs can be created. Assembly Language Assembly language is a low-level programming language - it is closer to machine code (binary) than high-level programming languages like Python. Assembly language uses mnemonics (abbreviations of commands) to signify instructions; for example, input is written as INP and output is written as OUT . Little Man Computer is a representation of assembly language . This simulator will help you understand assembly language and allow you to check if your instructions are correct. Assembly Language Mnemonics INP (Input) INP is used to input a number . The number is temporarily stored in the accumulator . OUT (Output) OUT is used to output the number currently stored in the accumulator . STA (Store) STA stores the value that is currently in the accumulator . It can be used to assign a value to a variable. ADD (Addition) ADD is used to add a number to the value currently stored in the accumulator. SUB (Subtraction) SUB takes away a number from the value currently stored in the accumulator. LDA (Load) LDA is used to load the value of a stored variable back into the accumulator . BRZ (Branch if Zero) BRZ is used to loop only if the value in the accumulator is currently 0 . BRP (Branch if Positive) BRP is used to loop only if the value in the accumulator is currently positive (including 0). BRA (Branch Always) BRA is used to loop continuously . HLT (Halt) HLT will stop running the program . Every program MUST have a HLT command. DAT (Data Definition) DAT must be used to define a variable name (and / or set it with a starting value). Data definitions must be written at the end of the instructions . Peter Higginson's Little Man Computer simulation Examples of Simple Assembly Language Programs #1 - Input & Output Program Purpose: Input a number, store the number as a variable called Number1 and output the number. 1. Lets the user input a number 3. Outputs the value in the accumulator - which will be the number that was just inputted. 5. Defines a variable called 'Number1'. This has to be at the end of the program and you must write the variable name first, not the command first. INP STA Number1 OUT HLT Number1 DAT 2. Stores the number in a variable named 'Number1' - there must be no spaces in a variable name. 4. Halts (stops) the program. Type these instructions line by line into the Little Man Computer simulator to see how it works. #2 - Addition Program Purpose: Input and store two numbers. Add them together. Output the total. 1. Lets the user input a number 3. Lets the user input another number 5. Adds number1 to the value in the accumulator (which is currently number2 as you just inputted it). 7. Halts the program. Type these instructions line by line into the Little Man Computer simulator to see how it works. Then change the program to subtract the number instead. INP STA Number1 INP STA Number2 ADD Number1 OUT HLT Number1 DAT Number2 DAT 2. Stores the inputted number in a variable named 'Number1'. 4. Stores the inputted number in a variable named 'Number2'. 6. Outputs the value in the accumulator (which is now number1 added to number2. 8. & 9. The two variables Number1 and Number2 are defined on separate lines. #3 - Load in Order Program Purpose: Input and store three numbers. Load and output them in the order that they were entered. 1. - 6. Lets the user input three numbers and immediately stores each one as they are entered. 8. Now that Number1 has been loaded into the accumulator, this value is outputted. 13. Halts the program. Type these instructions line by line into the Little Man Computer simulator to see how it works. Let the user input a fourth number and output this fourth number last . INP STA Number1 INP STA Number2 INP STA Number3 LDA Number1 OUT LDA Number2 OUT LDA Number3 OUT HLT Number1 DAT Number2 DAT Number3 DAT 14. - 16. The three variables Number1, Number2 & Number3 are defined on separate lines. 9. - 12. Number2 is loaded and output then Number3 is loaded and output 7. Once all three numbers have been inputted and stored, the first number is loaded back into the accumulator. #4 - Branching Program Purpose: Input and store two numbers. Output the largest number. (Branching required). 1. - 4. Lets the user input two numbers and immediately stores each one as they are entered. 7. BRP is 'Branch is Positive'. If the result of Number1 - Number2 is positive then the program will jump to line 11. You can write any value instead of 'loop', such as 'jump' or 'break'. If the result is not positive it will continue to the next line. 11. - 13. The program will jump to line 11 if the result of Number1 - Number2 is positive. This means that Number1 is larger than Number2 so Number1 is loaded and output then the program is halted. INP STA Number1 INP STA Number2 LDA Number1 SUB Number2 BRP loop LDA Number2 OUT HLT loop LDA Number1 OUT HLT Number1 DAT Number2 DAT 5. & 6. Loads Number1 and subtracts Number2 from it. 8. - 10. The program will continue to line 8 if the result of Number1 - Number2 is not positive. Because the result is a negative number, this tells us that Number2 is larger than Number1. So we load Number2, output it because it is bigger, then halt the program. 14. - 15. The variables Number1 & Number2 are defined on separate lines. Type these instructions line by line into the Little Man Computer simulator to see how it works. Change the program so that the smallest number is output .

Learn about the purpose and characteristics of the eight application types, including examples. Application types include communication, educational, entertainment, games, lifestyle, productivity, protection & utility and web browsers. Resources 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) 1.3.1 - Application Types Watch on YouTube : Application Types There are several types of applications that can be developed , each with a different purpose and common characteristics . There are eight application types you need to know for this 'Fundamentals of Application Development ' unit, including their purpose and common characteristics . Communication Purpose: Communication applications allow users to exchange information with others , most often in real-time . Data can be transferred in a range of formats including text , images and video . Education Purpose: To teach users about specific topics and help people learn new skills . This may be aimed at certain ages or user groups such as those learning a new language . Characteristics of Communication Applications: Has a simple user interface designed for quick and reliable data exchange . Supports multiple formats (text , images , audio , video and files ). Requires a network connection to send and receive data . Often has built-in security and privacy , such as end-to-end encryption . May use presence awareness such as showing ‘typing… ’ or ‘online now ’. Characteristics of Education Applications: It may be structured around learning milestones or long-term goals . Often interactive , such as quick quizzes or regular recaps of topics. Could include different formats of learning (such as text , visuals or audio ). Usually tracks skills or scores over time to show progress in a user-friendly way . Age-appropriate in content and design , possibly with difficulty levels . Examples: WhatsApp, Messenger, Zoom, Slack, Gmail Examples: Duolingo, Kahoot!, Quizlet, Memrise, Anki Entertainment Purpose: To provide enjoyment through formats such as video or audio , often with automatic suggestions based on previous interactions including watched videos , likes or comments . Characteristics of Entertainment Applications: Simple design to focus on keeping users engaged . May include streamed media content or the option to download . Designed for passive or relaxed use , e.g. watching or listening without interacting . Uses algorithms for recommendations based on user preferences . May include social features such as comments or sharing with friends . Examples: Netflix, Disney+, Spotify, YouTube, Twitch Games Purpose: To offer interactive challenges in a fun and possibly competitive way. Games may be played together online or offline for a single-player experience . Characteristics of Game Applications: Based on clear rules and objectives with reward systems , e.g. achievements . High interactivity and quick responsiveness to keep players engaged . Requires graphical rendering , user inputs and sound design . May support local multiplayer or online play with competition , like leaderboards . Often has a range of difficulty levels to keep players challenged . Examples: Minecraft, Fortnite, Among Us, EA Sports FC, Candy Crush Lifestyle Purpose: Supports a healthy and organised way of living . They often help people to manage their daily tasks and form positive personal routines . Productivity Purpose: To support users to complete tasks , manage their time or organise information in a helpful way , all to to maximise productivity . Characteristics of Lifestyle Applications: Often personalised to user preferences or personal data . May use real-time inputs such as location or health data , like steps taken . It may be integrated with smart wearable devices such as a smartwatch . Designed to be used briefly but daily (e.g. checking steps or logging meals ). Encourages improved habits or healthier improvements . Characteristics of Productivity Applications: Has a focus on efficiency , reliability and easy usability . Often allows collaboration and file sharing (e.g. working with colleagues ). Prioritises data organisation and quick access to relevant information . Usually integrated with cloud services or other apps like calendars . It may be designed for professional , personal or educational use . Examples: MyFitness Pal, Noom, Headspace, FitBit, Couch to 5k Examples: Microsoft Word, Calendar, Google Drive, Notion, Trello Protection & Utility Purpose: To secure the computer system against malicious threats and perform housekeeping tasks that maintain stability and a smooth performance . Characteristics of Protection & Utility Applications: Works in the background without frequent user interaction . Often requires permissions to access sensitive data . Needs to be updated frequently , e.g. adding new virus signatures to the database of an antivirus . May be event-driven (e.g. alerts or automatic scans at regular intervals ). Should use low system resources if it needs to be running constantly . Web Browsers Purpose: Accesses , retrieves and displays web pages from web servers . It provides tools like bookmarks , tabs and history to help users easily navigate the interne t. Characteristics of Web Browser Applications: Displays webpages that are built using HTML , CSS and JavaScript . Supports security protocols such as HTTPS , which uses encryption . Enables customisation and user control , e.g. bookmarks , extensions and themes . Contains an address bar to directly type in URLs or search terms . Allows for multiple tabs to run concurrently . Types of Application Examples: Avast Antivirus, CCleaner, 1Password, Battery Saver, Microsoft Defender Examples: Google Chrome, Safari, Mozilla Firefox, Microsoft Edge, Opera Q uesto's Q uestions 1.3.1 - Application Types: 1. Choose four application types and explain how each can be used in a school . [8 ] 2a. For two application types you did not mention in Q1 , explain their characteristics . [6 ] 2a. For the remaining two application types you have not mentioned , explain their purpose . [ 4 ] Minecraft is the best-selling video game of all time , with over 350 million copies sold since its official release in 2011 . D id Y ou K now? 1.2 - Operating Systems Topic List 1.3.2 - Application Software Categories

A simple Python editor using the Skulpt and Code Mirror libraries. Learn how to create simple programs in Python. Try practice tasks and learn through text and images. Perfect for students learning GCSE Computer Science in UK schools. Simple Python Editor You can use this simple Python editor below to complete most of the tasks in the CSNewbs Python sections (except colorama and text files ). It includes basic libraries such as random and time . When you're ready, click 'Run Code ' to see the result in the output below . Python Homepage

Learn about the seven steps of the fetch-decode-execute cycle and important registers in the CPU. Based on the 2020 Eduqas (WJEC) GCSE specification. 1.2: The FDE Cycle Exam Board: Eduqas Specification: 2020 The Fetch - Decode - Execute (FDE) cycle is performed by the CPU millions of times every second. This cycle is how the CPU processes data and instructions for each program or service that requires its attention. Important Registers A register is a small storage space for temporary data in the CPU . Each register has a specific role . There are five essential registers used in the FDE cycle : Program Counter (PC) A register that tracks the RAM address of the next instruction to be fetched . Memory Address Register (MAR) A register that tracks the RAM address of the instruction that is to be fetched . Memory Data Register (MDR) The MDR stores the instruction that has been transferred from RAM to the CPU . Current Instruction Register (CIR) A register that stores the instruction that has been fetched from RAM , and is about to be decoded or executed . Accumulator (ACC) The ACC stores the result of mathematical or logical calculations . Fetch - Decode - Execute Cycle The essential idea of the FDE cycle is that instructions are fetched from RAM , to be decoded (understood) and executed (processed) by the CPU . 1. The Program Counter (PC ) register displays the address in RAM of the next instruction to be processed . This value is copied into the Memory Address Register (MAR ). 0054 2. The PC register is increased by 1 . This prepares the CPU for the next instruction to be fetched. 0055 3. The CPU checks the address in RAM which matches the address held in the MAR . 0054 4. The instruction in RAM is transferred to the Memory Data Register (MDR ). 5. The instruction in the MDR is copied into the Current Instruction Register (CIR ). MDR MDR CIR 6. The instruction in the CIR is decoded (understood) and executed (processed). Any result of an execution is stored in the Accumulator (ACC ) register. CIR ACC 7. The cycle repeats by returning to the first step and checking the program counter for the address of the next instruction . Q uesto's Q uestions 1.2 - The Fetch - Decode - Execute (FDE) Cycle: 1 . What is the purpose of the registers ? [1 ] 2 . Describe the purpose of each register : a. The Program Counter (PC) [ 1 ] b. The Memory Address Register (MAR) [ 1 ] c. The Memory Data Register (MDR) [ 1 ] d. The Current Instruction Register (CIR) [ 1 ] e. The Accumulator (ACC) [ 1 ] 3. Draw a diagram of the seven steps of the Fetch - Decode - Execute cycle . [7 ] 1.1 - The CPU 1.3 - Primary Storage Theory Topics

Learn how to edit code in Greenfoot to make objects move using the arrow keys. Use methods such as isKeyDown, setRotation and move. Part 2 of the Greenfoot Tutorial for the Eduqas / WJEC GCSE 2016 specification. Right-click on your main character class and select ' Open editor '. The editor allows you to write different methods - actions that the class can perform. The act() method will repeat whenever the Run button is pressed. 1. Open the Code Editor 2. Movement with the Arrow Keys Greenfoot Tutorial Watch on YouTube: 2. Copy the Code CAREFULLY You need to use an if statement to check if a certain key (like the right arrow key) is being pressed down . An if statement must be contained in standard brackets . After each if statement, the proceeding code must be typed within curly brackets - see the image on the left . Tip - If the brackets are on the same line then use the standard brackets ( and ) If the brackets are on different lines then use curly brackets { and } Your code must be perfect or it won't work. 'Greenfoot ' requires a capital G and the isKeyDown method most be written with a lowercase i but uppercase K and D . When the right arrow key is pressed the object will change its rotation to 0° which is right . It will also move 1 place in this direction. Rotations in Greenfoot: 3. Code the Other Arrow Keys Directly underneath the if statement for turning and moving right, add the code for turning and moving down . You can see in the diagram above the degrees to rotate in each of the four directions . Write the code to move in all four directions. Ensure you have the correct number of brackets or the program won't start. Remember brackets that start and end on the same line are ( ) and brackets over multiple lines are { } . 4. 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 . Press the arrow keys to test your main character moves . Click on me if you've got an error that you're stuck with. < Part 1 - Setup & Populating the World Part 3 - Movement (Random) >

Learn about arrays, records and SQL (structured query language) including the SELECT, FROM and WHERE commands. Based on the J277 OCR GCSE Computer Science specification (first taught from 2020 onwards). Exam Board: OCR Specification: J277 2.3: Additional Programming Techniques Watch on YouTube : String Manipulation File Handling Arrays Subprograms Random Numbers SQL This section of the specification includes programming topics that are outlined in 1.2 (Designing Algorithms). You must have an understanding of more complex programming techniques , such as how to manipulate strings , handle files and use subprograms . The best practice for learning is to try the tasks in the Python pages on this website (see the link to the right). Visit the Python section of CSNewbs ---> Subprograms What is a subprogram? Large programs are often broken down into smaller subprograms (also called subroutines ). Each subprogram focuses on a specific function of the code, helping to decompose a complex problem into more manageable chunks . Defining subprograms A subprogram is defined (identified) using the def command in Python. A program may use many subprograms , which are usually defined at the start of the code . Calling subprograms Running a line of code that includes the name of a subprogram will call (activate) it. When called , the program will run the subprogram code before returning back to the line that called it . Subprograms are only run when called , so depending on decisions made, a program may end without calling every (or any) subroutine. Parameters A parameter is a value that is passed into a subprogram when it is called , allowing the value to be used within the subprogram . A subprogram may not use a parameter , e.g. multiply() , or one parameter , e.g. multiply(num) , or several e.g. multiply(num1,num2) . Any parameters must be identified when the subprogram is defined , e.g. def multiply(num): Return The return command will send a value back to the line the subprogram was called on, allowing it to be used there . For example, the 'quad' subprogram in the example below returns the value of the 'result' variable back to the main program, allowing it to be printed . A subprogram will end either by reaching the last line of code within it, or when it reaches a return command . Subprograms that return a value are called functions . Subprogram example This subprogram is defined using the identifier 'quad ' with a parameter named number . The subprogram is called in the main program, multiplies the number passed in as a parameter by 4 and returns a value back to the main program to be printed. def quad (number): result = number * 4 return result #Main Program number = int ( input ( "Enter a number: " )) print ( "The number quadrupled is" , quad(number)) Enter a number: 5 The number quadrupled is 20 Functions and Procedures There are two types of subprograms . A function is a subprogram that returns a value , using the return command, which allows the value to be used in the line of code the function was called in. The 'divide' function below returns the value of the variable 'total' to the main program to be printed. A procedure is a subprogram that does not return a value . Example of a Procedure def multiply (num): total = num * 2 print ( "The number doubled is" , total) #Main Program num = int ( input ( "Enter a number: " )) multiply(num) Enter a number: 4 The number doubled is 8 Example of a Function def divide (num): total = num / 2 return total #Main Program num = int ( input ( "Enter a number: " )) print ( "The number halved is" , divide(num)) Enter a number: 9 The number halved is 4.5 Advantages of using subprograms Subprograms break a complex program down into smaller parts , making it easier to design and test . Each subroutine can be tested separately and abstraction can be used to simplify a complicated problem . Using subprograms allows code to be easily reused in other programs , as it has already been written , making it quicker to develop new programs or build on existing work. Using subprograms avoids code repetition , as they can be called as many times as necessary . This makes programs shorter and quicker to develop , making them easier to maintain and debug . Work can easily be split up between team members to work on different subprograms at the same time . Array An array is a static data structure that can hold a fixed number of data elements . Each data element must be of the same data type i.e. real, integer, string. The elements in an array are identified by a number that indicates their position in the array. This number is known as the index. The first element in an array always has an index of 0 . You should know how to write pseudo code that manipulates arrays to traverse , add , remove and search for data . The following steps use Python as an example, although Python does not use arrays and uses a similar data structure called a list (that can change in size as the program runs ). See the 8a and 8b Python pages for tasks on how to use lists . What Traversing an Array To traverse (' move through ') an array a for loop can be used to display each data element in order. Example code for traversing: Output: 'Inserting' a value In an array the size is fixed so you cannot insert new values, but you can change the value of elements that already exist. Overwriting the fourth element (Daphne) with a new value (Laura) will change it from Daphne to Laura. Example code for inserting: Output: 'Deleting' a value In an array the size is fixed so you cannot delete values, but you can overwrite them as blank . Overwriting the second element (Shaggy) with a blank space makes it appear deleted. Example code for deleting: Output: Searching an Array For large arrays a for loop is needed to search through each element for a specific value . This example checks each name to see if it is equal to Velma. Example code for searching: Output: Two-Dimensional Array Often the data we want to process comes in the form of a table . The data in a two dimensional array must still all be of the same data type , but can have multiple rows and columns . The two-dimensional array to the right shows the characters from Scooby Doo along with their associated colour and their species. Each value in the array is represented by an index still, but now the index has two values . For example [3] [0] is 'Daphne'. Unless stated in an exam , measure row first , then column . Searching a two-dimensional array: To print a specific data element you can just use the index number like Daphne above. To search for a specific value you will need two for loops , one for the row and another for the values of each row . The example to the right is looking for the value of ' Velma ' and when it is found it prints the associated data from the whole row . Example code for printing: Output: Example code for searching: Output: Records Unlike arrays, records can store data of different data types . Each record is made up of information about one person or thing . Each piece of information in the record is called a field (each row name). Records should have a key field - this is unique data that identifies each record . For example Student ID is a good key field for a record on students as no two students can have the same Student ID. A 2D array may be used to represent database tables of records and fields . SQL SQL (structured query language ) is a language that can be used to search for data in a database . The format of an SQL statement is: SELECT field1, field2, field3… FROM table WHERE criteria Example of an SQL statement using the Cars table: SELECT Make, Colour FROM Cars WHERE Miles > 1000 AND Age > 8 Cars table SQL uses wildcards which are symbols used to substitute characters . The * symbol represents ALL fields . Example: SELECT * FROM Cars WHERE Colour = “blue” < Click the banner to try a self-marking quiz (Google Form) about records and SQL. Q uesto's Q uestions 2.3 - Additional Programming Techniques: 1a. Describe what the following terms mean: subprogram , parameter , function , procedure . [ 2 each ] 1b. Describe three advantages of using subprograms . [ 6 ] 2. Describe the differences between a 1D array , 2D array and record . [ 3 ] 3. A one-dimensional array looks like this: TigerBreeds["Sumatran","Indian","Malayan,"Amur"] Write the code to: a. Print the element with the index of 3. [ 2 ] b. Change Indian to South China. [ 2 ] c. Remove the Amur element. [ 2 ] d. Search through the array for 'Malayan'. [ 2 ] 4a. Use the Cars table above to write the SQL statement to display the make and miles for cars that are grey OR blue . [ 3 ] 4b. Write an SQL statement to display all fields for cars that are 10 years old or less . [ 3 ] 2.2 Data Types Theory Topics 3.1 - Defensive Design