Describe and Design Algorithms
When teaching algorithms the curriculum often uses the terms describe or design. The intent of these words is to plan your algorithms on paper before you open the coding platform.
Describe of the game
Pseudocode is when you describe the functionality of the code using words.
Purpose of the game.
The purpose of this program is have 2 sprites. One will be “Scratchie the cat” and one will be a “blue balloon”. Scratchie will need to be able to move from side to side. The balloon will drop from the top of the stage. If Scratchie is touched by the balloon Scratch will disappear and lose one life. Scratchie will get 3 lives before the game ends.
Describe of the balloon code - how will it work?
When the green flag is clicked the balloon will start in at a particular location using the co-ordinates (-196, 134). The next lot of code will repeat 10 times picking a random position on the x co-ordinate (across the screen). The balloon will drop from the top of the screen with an increment of -10. The minus value will ensure the balloon drops down the screen and will repeat 50 times.
Designing with flowcharts
Once you have describe the function of the game you can then create a flowchart to illustrate the design of the code.
A flowchart of potential code for the balloon falling from the top of the Scratch stage.
Actual code in Scratch to make a balloon fall from the top of the stage.
Video of how to create the code in Scratch.
This is the first post in a series of posts that complement a video series titled Balloon on YouTube. To create the flowchart with beginners you could model this on the board and students could repeat the process or copy your process on paper. Using pseudocode (or pseudo-text) also encourages literacy in the context of digital technology by writing about the planning for the project. Pseudocode and flowcharts also introduce discussions about the design of your algorithm, it’s purpose and considering the needs of the end user. You could also discuss tier 2 and 3 vocabulary that is used in digital technologies.
Curriculum Links
Australian Curriculum
Generating and designing
follow and describe algorithms involving sequencing, comparison operators (branching) and iteration
design algorithms involving multiple alternatives (branching) and iteration
Producing and Implementing
implement simple algorithms as visual programs involving control structures and input
implement algorithms as visual programs involving control structures, variables and input
NSW Syllabus
ST2-DDT-01
uses a design process to create products to address user needs or opportunities
ST2-DDT-02
designs and uses algorithms, represents data and uses digital systems for a purpose
ST3-DDT-01
uses design processes to create, evaluate and modify designed solutions
ST3-DDT-02
creates, evaluates and modifies algorithms to code or control digital devices and systems
ST3-CWT-01
creates written texts to communicate understanding of scientific and technological concepts and processes