Be a Problem Solver Chapter Notes | Year 3 Computing IGCSE (Cambridge) PDF Download

Input and Output

• Inputs and outputs are integral to everyday activities, where an action (input) leads to a result (output).
• Example: Using a remote control to change the television channel:
  • Input: The user presses the keys on the remote.
  • Output: The television changes channel.

You Will Learn

• To identify the inputs to algorithms.
• To create algorithms that produce an output from a given input.
• To code programs in Scratch that reset objects to their original state.
• The unit focuses on using Scratch to code programs.

Do You Remember?

• Before starting this unit, ensure you can:
  • Follow and understand algorithms.
  • Identify the steps in tasks and create algorithms.
  • Create programs with multiple algorithms running simultaneously.
• There is an online chapter dedicated to Scratch for further reference.

Identifying Inputs

• An algorithm is a set of instructions designed to complete a task.
• Every algorithm consists of two main parts: input and output.
• Keywords:
  • Input: Data that is given to an algorithm.
  • Output: The result of processing the input.
• An algorithm can have one or more inputs.
• Example: Algorithm for making orange juice:
  • Steps:
    1. Start
    2. Gather the ingredients: water, sugar, and orange juice concentrate.
    3. Add water to jug.
    4. Add juice concentrate to jug.
    5. Add sugar to jug.
    6. Mix all ingredients together with a spoon.
    7. Serve juice in a glass.
    8. Stop
  • Inputs: Water, sugar, orange juice concentrate.
  • Output: Finished orange juice.
• Example: Algorithm for adding two numbers:
  • Steps:
    1. Start
    2. Enter first number.
    3. Enter second number.
    4. Let answer = first number + second number.
    5. Show the answer.
    6. Stop
  • Inputs: First number, second number (Steps 2 and 3).
  • Output: The sum of the two numbers (Step 5).
  • Example execution: Enter first number: 2, Enter second number: 5, Output: Answer = 7.

Linear Algorithms

• Objective: Create two algorithms for a horse to move, each with an input and an output.
• Algorithm A: Resets the horse to its starting position.
  • Input: Clicking the Green flag.
  • Output: Setting the horse position to x = −100, y = −45.
  • Steps:
    1. Start program when Green Flag is clicked.
    2. Set horse position to x = −100, y = −45.
    3. Stop program.
• Algorithm B: Moves the horse to a random location.
  • Input: Clicking on the horse.
  • Outputs:
    • The horse switches costume after one second.
    • The horse moves to a random position on the screen.
  • Steps:
    1. Start program when sprite is clicked.
    2. Switch costume to horse-b.
    3. Wait 1 second.
    4. Switch costume to horse-a.
    5. Go to random position.
    6. Stop program.

Coding Linear Algorithms

• Steps to create the program for Algorithm A in Scratch:
  1. Create a new project in Scratch and delete Sprite 1.
  2. Search and select the Farm backdrop.
  3. Search and select the Horse sprite.
  4. Under the Events group of blocks, select the "when Green flag clicked" block.
  5. Under the Motion group of blocks, select the "go to x, y" block. Change the number for x to −100 and y to −45.
• Result: The code resets the sprite to the specified position.
• Steps to create the program for Algorithm B in Scratch (keeping Algorithm A code):
  1. Under the Events group of blocks, select the "when this sprite clicked" block.
  2. Under the Looks group of blocks, select the "switch costume to" block. Select horse-b from the dropdown.
  3. Under the Control group of blocks, select the "wait () seconds" block. Keep the default as 1 second.
  4. Under the Looks group of blocks, select the "switch costume to" block. Select horse-a from the dropdown.
  5. Under the Motion group of blocks, select the "go to ()" block. Keep the default as random position.
• Running the program:
  1. Click the Green flag: The Horse goes to its starting position (x = −100, y = −45).
  2. Click on the Horse:
     • The Horse switches to horse-b costume and waits one second.
     • The Horse moves to a random position and switches to horse-a costume simultaneously.

Go Further

• Algorithm for making pizza dough:
  • Steps:
    1. Start
    2. Gather the ingredients: flour, sugar, yeast, salt, water, oil.
    3. Mix the dry ingredients in a bowl.
    4. Add the water and oil into the bowl while mixing.
    5. Mix until the dough forms into a ball.
    6. Let dough sit for 1 hour until it doubles in size.
    7. Roll out the dough with a rolling pin.
    8. Place dough into pan.
    9. Stop
  • Inputs: Flour, sugar, yeast, salt, water, oil.
  • Output: Prepared pizza dough in a pan.
• Algorithm for adding the vegetables:
  • Steps:
    1. Start
    2. Gather the ingredients: pizza sauce, tomatoes, mushrooms, green peppers, cheese.
    3. Add pizza sauce to dough.
    4. Slice tomatoes.
    5. Cut green peppers.
    6. Cut mushrooms.
    7. Grate cheese.
    8. Place all vegetables on top of dough.
    9. Stop
  • Inputs: Pizza sauce, tomatoes, mushrooms, green peppers, cheese.
  • Output: Pizza dough topped with sauce and vegetables.
• Algorithm for baking the pizza:
  • Steps:
    1. Start
    2. Set the oven to 425 degrees.
    3. Add uncooked pizza to oven.
    4. Bake for 15 minutes.
    5. Remove cooked pizza from oven.
    6. Stop
  • Input: Uncooked pizza.
  • Output: Cooked pizza.

Did You Know?

• Inputs and outputs are ubiquitous in daily life.
• Example: In the human body:
  • Inputs: Food and water.
  • Output: Energy that powers the body, enabling movement, thinking, and heart function.

What Can You Do?

• Skills achieved:
  • I can identify the inputs to algorithms.
  • I can create algorithms to give an output from an input.
  • I can reset objects in Scratch.
• With these skills, you can now use Scratch to code programs effectively.

Glossary

• App: Another name for software.
• Automatic: Collects data with little or no human input.
• Backup: An exact copy of the original file.
• Biometric: Measurements of the human body.
• Bug: An error in the program.
• Cipher: A set of rules to convert plain text to ciphertext.
• Ciphertext: Text that only people with the cipher can understand.
• Computer-controlled device: A machine that inputs data and performs a specific task.
• Computer virus: A program written to cause damage to data and software.
• Concise: Short.
• Decision: A choice about something.
• Edit: To change.
• Efficient: Getting a result using the least amount of time or steps.
• E-reader: A device that lets you read electronic books.
• Error: A mistake.
• Format: The way something looks.
• Hardware: Physical objects that make up the computer.
• Input: Data that is given to an algorithm.
• Interactive smartboard: A whiteboard connected to a computer and a projector.
• Internet of Things: Smart devices connected to the internet.
• Logical thinking: To understand a problem and come up with a solution that makes sense.
• Manual: Needs human input.
• Multifunction: Does more than one thing.
• Numerical: Made of numbers.
• Output: The result of processing the input.
• Plain text: Any set of letters, words, or numbers that anyone can understand.
• Range: A group of selected cells.
• Repetitive: Doing the same thing over and over again.
• Reset: To return to the original state.
• RFID: A type of tracking device.
• Services: Things that can be done on a network.
• Smart device: An electronic device that is connected to other devices via the internet.
• Software: A computer program, the set of instructions that a computer follows to perform a task.
• Static objects: Sprites that do not have any code.
• Sub-task: A task that is part of a more complex task.
• Volume: How loudly or quietly a sound is played.
• World Wide Web: A service on the internet to find and show web pages.