In this lesson, you'll build on your understanding of algorithms and flowcharts, and learn about pseudocode as a tool for planning code. You'll create your own flowcharts and pseudocode, then see how they translate into a simple program using MakeCode for micro:bit. By the end, you'll design your own algorithm from scratch.

Here's what you'll cover:

1. Recapping flowcharts and their key shapes.
2. Creating a flowchart for an online shopping cart.
3. Introducing pseudocode and its features.
4. Writing pseudocode based on your flowchart.
5. Coding a temperature reaction program in MakeCode.
6. Designing your own algorithm with a flowchart and pseudocode.

In the previous lesson we introduced you to algorithms and flowcharts, let's recap what we learned.

Algorithm

An algorithm is simply a step-by-step set of instructions that helps you solve a problem or complete a task. Imagine it as a clear guide that tells you exactly what to do, one thing at a time, in the right order, so you end up with the result you want.

Key Properties

1. Precise - every step is clearly defined, like "add 2 cups of flour" not "add some flour"
2. Finite - it ends after a fixed number of steps, like a recipe that finishes when the cake is baked
3. Effective - it solves the problem correctly, like a sorting algorithm that always sorts the list properly
4. Efficient - it does the job with minimal steps or time, like quicksort vs bubble sort

Flowcharts

Flowcharts are visual representations of algorithms using shapes and arrows to show the flow of steps and decisions.

Basic Shapes

Oval

Used for the start and end of the algorithm. It marks where the process begins and finishes.

Rectangle

Represents a process or action step, like "Display a message" or "Calculate a sum".

Diamond

Indicates a decision point, where the flow branches based on a yes/no question, such as "Is it raining?".

Parallelogram

Often used for input or output, like reading data from a user or showing results.

Arrow

Shows the direction of the flow, connecting the shapes in the correct order.

Example Flowchart

Here's a simple flowchart for making a decision about going outside based on the weather: It starts with an oval 'Start', then a diamond decision 'Is it raining?', with 'Yes' leading to a rectangle 'Take umbrella' and 'No' leading to a rectangle 'Enjoy the sun', both connecting to an oval 'End'.

Now it's time to practise creating your own flowchart. You'll design a simple flowchart for an online shopping cart process using the tool you've used before at www.drawio.com.

The flowchart should represent a basic online shopping experience: starting from browsing items, deciding to add to cart, continuing shopping or checking out, and ending with payment confirmation.

Let's move on to another important tool for planning algorithms: pseudocode. Pseudocode is a way to describe the steps of an algorithm using simple, human-readable language that looks a bit like programming code, but without worrying about the exact rules of a specific programming language. It bridges your flowchart to potential code.

What is Pseudocode?

Pseudocode acts as a bridge between your ideas (like those in a flowchart) and actual code. It helps you outline the logic of your program clearly before you start coding. This makes it easier to spot mistakes early and ensures your algorithm is precise, finite, effective, and efficient.

Key Features of Pseudocode

1. Readable: It uses everyday words mixed with code-like structures, so anyone can understand it.
2. Flexible: No strict syntax – you don't have to worry about semicolons or brackets.
3. Structured: It often includes keywords like IF, ELSE, WHILE, FOR, to show decisions and loops.

Common Elements

• Variables: Assign values, e.g., SET age TO 16
• Input/Output: READ input or DISPLAY message
• Decisions: IF condition THEN ... ELSE ... END IF
• Loops: WHILE condition DO ... END WHILE or REPEAT ... UNTIL condition
• Start/End: Often begins with START and ends with END

Example Pseudocode

Remember the weather flowchart from earlier? Here's how it might look in pseudocode:

This matches the flowchart's decision diamond and process rectangles, but in text form. It's simple and helps you think through the steps before coding.