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Learn about project planning tools such as the Arrow diagram, Critical Path Analysis (CPA)/Critical Path Method (CPM), Flowcharts, Gantt charts, PERT charts and SWOT (Strengths / Weaknesses / Opportunities / Threats) analysis. 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) 3.2 - Project Planning Tools Watch on YouTube : Project planning tools Arrow diagram Critical path analysis Flowcharts Gantt charts PERT charts SWOT analysis Project Planning Tools Project planning tools help to visualise the project by clearly showing tasks , timelines and dependencies . They also break down complex work into smaller , manageable steps and can be used to track progress and identify delays . Each tool suits different project needs and has its own advantages and disadvantages . Choosing the right tool makes planning more accurate , efficient and successful . Arrow Diagram The arrow diagram method is a project planning tool that represents tasks as arrows connected in sequence to show their order and dependencies . It helps identify the critical path . This is the longest sequence of dependent tasks that determines the project’s minimum completion time . This method is useful for visualising task relationships , spotting bottlenecks and showing the order of activities . Critical Path Analysis Critical path analysis ( CPA ), also known as the critical path method ( CPM ), is a project planning tool used to identify the critical path . This is the sequence of tasks that determines the shortest possible project duration . It highlights tasks that cannot be delayed without affecting the overall timeline . Critical path analysis helps prioritise resources , manage dependencies and minimise project delays . Flowcharts A flowchart is a diagram that represents a process or workflow using standard symbols and arrows to show the sequence of steps . It helps visualise decision points and actions and clearly highlights the flow of information or tasks . Flowcharts make complex processes easier to understand , communicate ideas to clients and troubleshoot potential problems . Gantt Charts A Gantt chart is a visual project management tool that displays tasks along a timeline , showing their start and end dates . It helps track task dependencies , overlaps and progress at a glance . Gantt charts are useful for coordinating work , meeting deadlines and ensuring all project stages are completed in order . PERT Charts A PERT ( program evaluation and review technique ) chart is a project planning tool that maps tasks , their dependencies and timelines in a network diagram . It uses three time estimates ( optimistic , most likely and pessimistic ) to calculate expected completion times for each task . PERT charts are especially useful for scheduling complex projects and identifying the critical path to meet deadlines . SWOT Analysis SWOT analysis is a strategic planning tool used to identify a project’s strengths , weaknesses , opportunities and threats . Strengths and weaknesses focus on internal factors ( controllable by the organisation ), while opportunities and threats look at external influences ( outside of the organisation's control ). It helps guide decision-making by highlighting advantages , weaknesses to address and potential risks or openings in the wider environment . Q uesto's Q uestions 3.2 - Project Planning Tools: 1. Define the term 'critical path ' and explain why it is calculated . [3 ] 2. Explain the S , W , O and T in SWOT analysis (not just what they stand for). [4 ] 3. Choose three project planning tools and describe the advantages and disadvantages of each . [ 12 ] Henry Gantt , an American engineer , created the Gantt chart in the 1910s . It has been used as a planning tool in many major projects , including building the Hoover Dam . D id Y ou K now? 3.1 - Planning Projects Topic List 4.1 - Gathering Client Requirements

The third part of a quick guide to the basics of Python aimed at Key Stage 3 students. Learn about creating and using inputs. Python - #3 - Inputs 1. Asking Questions Input means to enter data into a program. Use the input command to ask a question. You must save the answer into a suitably named variable using the = symbol. Task 1 - Create a new Python program and save the file as 3-Inputs.py Use the picture to help you ask what someone's name is. Run the program and type your name. When you run the program (F5) you can type your answer on any question line in the Python Shell . 2. Asking more Questions There is no limit to how many questions you can ask in Python. It is the most important way to interact with the user of your program. Task 2 - Ask two more questions on topics of your choice. 3. Using Variables in a Sentence When we have printed the answers so far, they have not been very informative! You can print variables together with sentences so that they mean more. Use a comma ( , ) between variables and sentences . Task 3 - Use the pictures to help you add commas and sentences to your program to be more informative. BONUS: After I took the screenshot of my code I added in print lines in the two blanks spaces that print a line of dashes. Try to do the same to make your program easier to read. 4. Using Integers An integer is a whole number . When you are asking a question that you know will have a number for an answer , you need to add int ( before your input. Don't forget to add double close brackets at the end of the question line ! Task 4 - Underneath your previous questions (don't delete anything) ask 2 questions that will have numbers for answers. You must use int ( - see the image for help. Challenge Programs Use everything that you have learned on this page to help you create these programs... Challenge Task 1 - Funny Food Create a new Python program. Save it as ' 3-FunnyFood.py ' Add a comment at the top with your name and the date. Create a program that asks two questions, one for their favourite colour and one for their favourite food. Print a funny sentence using both of their answers. BONUS : Try to use only one print line. Remember: Break up variables in a print line by using commas. When you run it, it could look something like this: Challenge Task 2 - Trivia Question Create a new Python program. Save is as ' 3-Trivia.py ' Add a comment at the top with your name and the date. Create a program that asks the user a trivia question of your choice. Print the correct answer AND their answer. BONUS : Use only one print line. BONUS : Try to use only two lines in total . Remember: Break up variables in a print line by using commas. When you run it, it could look something like this: Challenge Task 3 - Getting to School Create a new Python program. Save it as ' 3-School.py ' Add a comment at the top with your name and the date. Create a program that asks two questions, one for how they get to school and one for how long it takes. Don't forget - use int( and then double close brackets for a number! Print an appropriate response that uses both of their answers. BONUS : Use two separate input lines. BONUS : Try to use only one print line . Remember: Break up variables in a print line by using commas. When you run it, it could look something like this: <<< #2 Variables #4 Calculations >>>

Learn about the different parts of computational thinking including thinking abstractly, ahead, procedurally, logically and concurrently. Based on the OCR H446 Computer Science A-Level specification. Exam Board: OCR A-Level Specification: Computer Science H446 1.1 - Computational Thinking Watch on YouTube : Thinking Abstractly Thinking Ahead Thinking Procedurally Thinking Logically Thinking Concurrently Computational thinking is the process of approaching and solving problems in a logical , systematic way (like a computer would ) using techniques such as abstraction , decomposition , pattern recognition and algorithmic thinking . There are five categories of computational thinking you need to know. Thinking Abstractly Abstraction is the process of removing unnecessary detail so that a problem can be represented more simply . It helps programmers focus on the essential features of a task, reducing complexity and making solutions easier to design , understand and maintain . When programming , abstraction can be applied by simplifying real-world systems into models that contain only the information needed for solving the problem . Because abstractions leave out certain details , they always differ from reality , and it is important to understand which elements have been included , which have been excluded and why . YouTube video uploading soon Thinking Ahead Programs often make use of inputs and outputs to receive data from the user or another system and then return results or feedback. Many programs rely on preconditions - rules or requirements that must be met before a function or procedure runs correctly - to prevent errors and ensure reliable behaviour . Caching is a technique where previously calculated or frequently accessed data is stored temporarily so it can be retrieved more quickly . This improves performance but can use extra memory and risks becoming outdated if the cached data no longer matches the current state . Reusable program components , such as functions , procedures and modules , are important because they reduce duplication , make programs easier to maintain , and allow well-tested code to be used across multiple solutions . YouTube video uploading soon Thinking Procedurally Pseudocode , program code and flowcharts are ways of representing a sequence of steps in an algorithm , showing clearly the order in which instructions should be carried out . Sub-procedures (such as functions and procedures ) are used in programs to break complex tasks into smaller , reusable parts , making the code easier to understand , test , maintain and debug . A structure diagram is a visual representation that shows how a program is broken down into its main components and sub-components , helping programmers plan the overall design and understand how different parts of the program fit together . YouTube video uploading soon Thinking Logically Decisions are needed in computer programs so that the software can choose different actions based on the data it receives or the situation it is in , rather than always following the same sequence of instructions. These decisions are controlled by logical conditions - statements that evaluate to true or false - which determine which path the program will take; for example, if score > 100 might trigger a bonus feature only when the condition is true . Because decisions allow the program to branch , they directly affect the flow of execution , enabling different outcomes , repeated actions or alternative processes depending on the conditions met . YouTube video uploading soon Thinking Concurrently Concurrency means designing a program so that multiple tasks can be processed at the same time , rather than strictly one after another. Programmers need to identify which parts of a program can safely run concurrently - for example, independent calculations or background tasks - and which parts must wait for others to finish because they rely on shared data or sequential results . Concurrent processing can bring benefits such as faster performance , better use of multicore processors and improved responsiveness , but it also introduces drawbacks, including increased complexity and the need for careful coordination to avoid errors when tasks depend on one another . YouTube video uploading soon This page is under active development. Check here for the latest progress update. Q uesto's K ey T erms Computational Thinking: abstraction, thinking abstractly, thinking ahead, precondition, caching, reusable components, thinking procedurally, thinking logically, concurrency, thinking concurrently D id Y ou K now? Building a Lego set is a great example of both abstraction and decompostition . For example, the Eiffel Tower Lego set is an abstracted version of it is real-life counterpart condensed into 10,001 pieces . There are over 75 numbered bags inside the box to follow instructions step-by-step to construct the 4'11" model . A-Level Topics 2.1 - Programming Techniques

Learn about the two types of data storage unit systems and how the increments work, including kilobyte and kibibyte. Based on the 2016 OCR Cambridge Technicals Level 3 IT specification. 1.7 - Units of Measurement Exam Board: OCR Specification: 2016 - Unit 1 All computer systems communicate , process and store data using binary because this is the format that the processor understands . Binary is a number system consisting entirely of 0s and 1s . A single binary data value (a 0 or a 1 ) is called a bit . 4 bits is called a nibble (e.g. 0101 or 1100). 8 bits is called a byte (e.g. 10101001 or 01011100). There are two main measurement systems : Metric Units of Measurement The gap between units when using metric values (also known as the decimal system ) is always 1,000 . For example, there are 1,000 bytes in 1 kilobyte and 1,000 kilobytes in 1 megabyte . To convert between metric units , divide by 1,000 when moving to a larger unit (e.g. 500 megabytes is 0.5 gigabytes ) and multiply by 1,000 when moving to a smaller unit (e.g. 4.7 terabytes is 4,700 gigabytes ). For example, 8,520 KB is the same as 8.52 MB or 0.00825 GB . Metric values (usually) have a prefix ending in ‘ a ’ such as mega byte or giga byte. Binary Units of Measurement The gap between units when using binary values is always 1,024 . For example, there are 1,024 bytes in 1 kibibyte and 1,024 kibibytes in 1 mebibyte . To convert between binary units , divide by 1,024 when moving to a larger unit (e.g. 4,096 kibibytes is 4 mebibytes ) and multiply by 1,024 when moving to a smaller unit (e.g. 55 pebibytes is 55,296 tebibytes ). For example, 34 KiB is the same as 34,816 MiB or 35,651,584 GiB . Bi nary values have a prefix ending in ‘ bi ’ , such as ki bi byte or me bi byte. Computer scientists often use the binary system of measurement because the storage size is technically more accurate . Q uesto's Q uestions 1.7 - Units of Measurement: 1 a. Create a table or list that clearly shows the relationship between values from bit up to petabyte for the metric (decimal) measurement system . [4 ] 1 b. Create another table to display the binary measurement system from bit to pebibyte . [4 ] 2. Make the following conversions and show your working out . [2 each ] a. 40 megabytes into kilobytes . b. 8500 gigabytes into terabytes . c. 100 mebibytes into kibibytes . d. 854,016 mebibytes into gibibytes . e. How many bytes are there in 3 megabytes ? f. How many bytes are there in 3 mebibytes ? 1.6 - Hardware Troubleshooting 1.8 & 1.9 - Number Systems Topic List

Learn about the purpose, characteristics, advantages, disadvantages, examples and client requirements of application software categories including open, closed, shareware, freeware and embedded software. 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) 1.3.2 - Application Software Categories Watch on YouTube : Open Software Closed Software Shareware Freeware Embedded Software There are five application software categories you need to know : Open Closed Shareware Freeware Embedded For each software category you need to know : Its purpose and common characteristics . The types of devices the software may be used on. The advantages and disadvantages of using the software. How client requirements affect the selection of that software. Application Categories Open Software Closed Software Open (usually known as open-source ) software is developed to be freely accessible and allow users to view , modify and distribute the source code . Its purpose is to promote collaboration and customisation when developing software . Closed (or closed-source or proprietary ) software is developed and distributed by a company or individual who owns the source code . The purpose is to maintain control , generate profit and ensure a consistent user experience . Shareware Shareware is closed software that is distributed for free on a trial basis , often with limited features or time restrictions . The purpose is to let users try before they buy , encouraging them to later purchase the full version . Freeware Freeware is closed software that is completely free to use , usually without restrictions like time limits or limited features , but still owned by a developer or company . The purpose is to provide software for free while retaining control over its code and distribution . Embedded Software Embedded software is designed to run on specific hardware and perform dedicated tasks . It is usually built into devices that are not traditional computers (like washing machines or microwaves ), allowing those devices to function efficiently and potentially automatically . Q uesto's Q uestions 1.3.2 - Application Software Categories: 1. Summarise the five categories of application software in two sentences each . [5 ] 2. An independent video game company has made a short game with just three levels. Justify which application software category they should use and why . [4 ] 3. Describe the advantages and disadvantages of using embedded software . [ 4 ] WinRAR is a shareware compression tool with a 40-day free trial , but it never actually locks users out. Since 1995 , WinRAR has been downloaded an estimated 500 million times . D id Y ou K now? 1.3.1 - Application Types Topic List 1.3.3 - Application Software Types

Test your understanding of working with files in Python, including reading, searching, writing and editing. Try practice tasks and learn through text and images. Perfect for students learning GCSE Computer Science in UK schools. Python - Section 10 Practice Tasks Task One Create a file in Python called DaysOfTheWeek.txt. Write the days of the week into the file in a single print line but put each day on a new line. Check the file to see if it has worked. Example solution: Task Two Create a file called Colours.txt. Use a for loop to ask the user to enter 8 different colours. Write each colour onto the same line, with a space between the colours. Close the file and open it again in read mode and print it. Example solution: Task Three Create a file named "Holiday.txt". Ask the user to enter the family name, destination and and number of passengers. Print each family's details on their own line. Bonus: Edit this program to add a search feature to look for the family name. Example solution: Task Four Use the holiday file from task three above. You are going to change the destination. Ask the user to enter a family name and then a new destination. Update the destination with the new value. Check the file to ensure the destination has been updated successfully. Use section 10c to help you with this task. Example solution: ⬅ 10c - Remove & Edit Lines 11 - Graphical User Interface ➡

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 4 Hi, Jacob Mortimer here from Cats & Dogs Veterinary Surgery . There was a flood last week, and our computer systems were totally destroyed . I need you to create a program , using a file , that allows my receptionist to: Add new animals to the file . Search through the file and print the details of a specific animal . Allow a specific animal to be removed from the file . Vet Surgery For this task, you will need to create a document and include the following sections (with screenshots where appropriate): An introduction to explain the Purpose of your program . A List of Requirements for a successful program. Screenshots of your code (with comments in your code to show understanding). Testing – Create a plan to show how you will test your program and then explanations of any errors that you found and how they were fixed . An Evaluation of what worked, what didn’t, and how you met each of your requirements from your original list. Also, discuss further improvements that you could have made to improve your program. Reminders for this task: You will need to create a selection of options for the user to choose from. Subroutines and a while true loop may help. Section 10 will help you to open, write and read from files . Section 10c shows how to edit data in a file. You will need to adapt this code and not write the line that has been selected, instead of writing a modified version of it. 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: Entering 1 allows the user to enter the details of a new animal which is saved into the file . Entering 4 will stop the loop and ends the program. Entering 2 allows the user to enter the details of an animal to search for . If the animal is in the file, their details are printed clearly on a new line. Entering 3 allows the user to enter the details of an animal to remove from the file . If the animal is in the file, all lines are transferred into a temporary file except for the line to be removed . ⬅ Extended Task 3 (Blackjack) Extended Task 5 (Colour Collection) ➡

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

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

Learn about the components of the Central Processing Unit (CPU) and Von Neumann architecture. Based on the J277 OCR GCSE Computer Science specification (first taught from 2020 onwards). Exam Board: OCR 1.1a: The CPU Specification: J277 Watch on YouTube : Purpose of the CPU CPU Components Von Neumann Architecture The Central Processing Unit ( CPU ) is the most important component in any computer system. Like many computer components, it is attached to the motherboard . The purpose of the CPU is to process data and instructions by constantly repeating the fetch-execute cycle . CPU Components The Control Unit (CU ) sends control signals to direct the operation of the CPU . Control signals and timing signals are sent to the ALU and other components such as RAM . It also decodes instructions as part of the fetch-execute cycle . ALU stands for ‘ Arithmetic and Logic Unit ’. It performs simple calculations and logical operations . A register is a temporary storage space for one instruction or address . Different registers are used during the fetch-execute cycle . Cache memory is used to temporarily store data that is frequently accessed . Cache memory is split into different levels . Cache is slower to access than the registers but much faster than RAM . Computer Architecture The way a computer is designed and structured is known as its architecture . The most common type of computer architecture is Von Neumann . It is named after the mathematician John Von Neumann (pronounced Von Noy-man) Von Neumann Architecture A computer with Von Neumann architecture stores both program instructions and data in the same memory (RAM ) and in the same format (in binary ). Instructions (technically called the opcode ) and data (technically called the operand ) are not the same . An instruction is an action to perform and data is the value to be used. For example with the command 'ADD 43 ', ADD is the instruction and 43 is the data . Von Neumann architecture also contains the key CPU components of a control unit , arithmetic logic unit (ALU ), registers and cache memory . Q uesto's Q uestions 1.1a - The CPU: 1a. What does 'CPU ' stand for ? [1 ] 1b. What is the purpose of the CPU ? [ 2 ] 2. Draw a diagram of the CPU , and l abel the four main components . [ 4 ] 3. Describe the purpose of: a. The Control Unit [ 2 ] b. The ALU [ 2 ] c. The registers [ 2 ] d. Cache memory [ 2 ] 4a. Describe the key feature of Von Neumann architecture . [ 2 ] 4b. Explain how an instruction is different to data . [ 2 ] 1.1b - Registers & FE Cycle Theory Topics

Learn how to handle errors in Python. Try practice tasks and learn through text and images. Perfect for students learning GCSE Computer Science in UK schools. 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) ➡

Learn about key registers used in the fetch - execute cycle such as the program counter and current instruction register. Based on the J277 OCR GCSE Computer Science specification (first taught from 2020 onwards). 1.1b: Registers & The F-E Cycle Exam Board: OCR Specification: J277 Watch on YouTube : Registers in the FE Cycle Reading instructions The fetch - execute (F-E) 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 requiring attention . Important Registers A register is a small storage space for temporary data in the CPU . Each register has a specific role . There are four essential registers used in the F-E cycle : Program Counter (PC) A register that tracks the RAM address of the next instruction to be fetched . Memory Address Register (MAR) Stores the RAM address of the current instruction (or data ) the CPU needs to access . Memory Data Register (MDR) The MDR stores the instruction that has been transferred from RAM to the CPU . Accumulator (ACC) The ACC stores the result of mathematical or logical calculations . The PC , MAR and MDR are used in the fetch stage , whereas the ACC is used in the execute stage . The PC and MAR store an address (a memory location in RAM ) whereas the MDR and ACC store data (a value ). Fetch - Execute Cycle The essential idea of the F-E 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 ). MDR 5. The instruction is decoded by the control unit which splits the instruction into an opcode (an action ) and an operand ( data or address ). 6. The instruction i s executed (run). Any result of an execution is stored in the Accumulator (ACC ) register, such as calculations made by the ALU . 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 1.1b - Registers & The F-E Cycle: 1 . What is the purpose of the registers ? [1 ] 2 . Describe the purpose of each register : a. The Program Counter (PC) [ 2 ] b. The Memory Address Register (MAR) [ 2 ] c. The Memory Data Register (MDR) [ 2 ] d. The Accumulator (ACC) [ 2 ] 3. Draw a diagram with icons and words to show the steps of the Fetch - Execute cycle . [7 ] 1.1a - The CPU Theory Topics 1.2 - CPU Performance