Chapter Notes: Making Programs Clear

Being Efficient

Efficient Programming

• This chapter focuses on learning how to follow, understand, edit, and correct algorithms to make them efficient.
• It emphasizes editing programs to simplify them and creating programs that reset objects.
• The programming tool used in this unit, which helps in creating and testing algorithms.
• It is recommended to specify where the online chapter about can be accessed to enhance learning.

Warm up

• The warm-up section introduces a scenario where a girl needs to reach her friends by following a specific algorithm.
• The algorithm involves hopping three times, jumping twice, and walking twice to reach the destination.
• The steps of the algorithm are outlined as:
  • Step 1: Start
  • Step 2: Hop forward
  • Step 3: Jump forward
  • Step 4: Walk forward
  • Step 5: Stop

Do you remember?
Before starting the unit, ensure the following skills are mastered:

• Ability to follow and understand algorithms.
• Ability to correct an algorithm with errors.
• Knowledge of writing precise instructions.
• Ability to create algorithms as programs.

Follow, understand, edit and correct algorithms

• An algorithm is defined as a set of instructions designed to perform a specific task.
• The steps of an algorithm must be in the correct order to ensure proper execution.
• It is essential to follow and understand an algorithm to determine if it functions correctly.
• If an algorithm does not work as intended, it must be edited and corrected to achieve the desired outcome.

Following and Understanding an Algorithm

• This section explores how algorithms guide users to a specific destination.
• An example involves a boy navigating to a friend's house using the following algorithm:
  • Move 3 blocks right
  • Move 4 blocks forward from the current position
  • Move 2 blocks left
  • Move 1 block forward
• Understanding the algorithm ensures it leads to the correct destination (e.g., the yellow or blue house).
• Verifying the algorithm confirms whether the boy reaches the intended house.

Algorithms for Editing and Correction

This section examines a scenario where a boy delivers a pizza using a given algorithm.

The original algorithm provided is:

• Move 3 blocks left
• Move 3 blocks forward
• Move 2 blocks right
• Move 2 blocks forward

Step-by-step analysis involves:

• Checking each instruction carefully.
• Following the instructions to see if the boy reaches the house.
• Identifying errors if the boy does not reach the destination.
• Making corrections to fix incorrect steps.

The corrected algorithm is:

• Move 1 block right (changed from Move 3 blocks left)
• Move 3 blocks forward
• Move 1 block right (changed from Move 2 blocks right)
• Move 2 blocks forward

• Verification ensures the corrected algorithm accurately leads to the house.

Concise Programs

Efficient algorithms accomplish tasks using the fewest possible steps, leading to efficient programs.
To make a program concise, the following techniques are used:

• Combine repeated code to reduce redundancy.
• Remove unnecessary code to simplify the program.

Combining and removing commands

An example compares two programs (Program A and Program B) that make a balloon float upwards while shrinking.

In Program A:

• The command "change y by 30" is used twice.
• The command "change y by 40" is used twice.
• The program consists of 8 blocks of code.

In Program B:

• The two "change y by 30" commands are combined into a single "change y by 60".
• The two "change y by 40" commands are combined into a single "change y by 80".
• The program is reduced to 6 blocks of code.

• Program B is more concise while achieving the same result as Program A.
• Keywords:
  • Efficient: Accomplishing a task in the least amount of time or steps.
  • Concise: Something that is short and to the point, without unnecessary elements.
• Example: Create a new  project where the Ripley sprite falls to the ground and grows larger as it descends.
• When the Green flag is clicked, the Ripley sprite should:
  • Move 40 positions down twice.
  • Pause for 1 second.
  • Grow by 10.
  • Move 50 positions down twice.
  • Grow by 15.
• Position the Ripley sprite as specified in the provided picture.
• Use the specified  blocks to create the program.
• Run the program to verify that Ripley falls and increases in size as it descends.

Resetting Objects

• This section introduces the concept of resetting objects, similar to video games where characters return to their starting positions.
• Resetting an object or character involves adding specific blocks of code to restore its original state.

Reset Position

• A sample code for the Cat sprite demonstrates movement across the screen when the Green flag is clicked.

• The Cat moves 400 steps forward with each click of the Green flag.
• Without resetting, clicking the Green flag again causes the Cat to walk off the screen's edge.
• To prevent this, a "Go To x: -200 y: 0" block is added after the "When Green flag clicked" block to reset the Cat's starting position.

• The negative sign in the x-coordinate (-200) is crucial to ensure the sprite is positioned correctly; omitting it places the sprite incorrectly.
• A "Wait" block is added before the "Move" block to prevent the sprite from appearing stationary during execution.

Reset Size

• The Cat sprite's code increases its size by 10 three times when the Green flag is clicked, causing it to grow with each run.
• Repeated execution without resetting results in excessive growth, which is problematic.
• To address this, a "Set the size to ( )" block is used to reset the sprite's size to its original value.

• The original size of any sprite is 100%, so the block is set to 100% to restore the Cat's initial size.
• Testing the reset ensures the Cat sprite returns to its original size each time the Green flag is clicked.

• When a sprite is added to a program, its default size is 100%, which can be increased for a larger sprite or decreased for a smaller one.
• Resetting is defined as returning an object to its original state, such as its initial position or size.