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An introduction to visual diagrams that represent the flow of an algorithm.
Have you ever tried to explain how to tie a shoelace to someone who has never seen a shoe? It’s harder than it looks! What if you could draw a 'treasure map' for instructions that anyone—or any computer—could follow perfectly?
Before a programmer writes a single line of code, they need a plan. A flowchart is a visual diagram that shows the step-by-step 'flow' of an algorithm. Think of it as a map where arrows tell you exactly which way to go next. Instead of reading a long wall of text, your eyes follow the shapes to see how a task gets done from start to finish. In computer science, we use specific shapes to represent different types of actions. For example, every flowchart must have a clear beginning and end, usually shown as an Oval.
Let's look at a simple linear process: 1. Oval (Start): The alarm rings. 2. Rectangle (Process): You hit the 'Snooze' button. 3. Rectangle (Process): You wait minutes. 4. Oval (End): The alarm rings again.
Quick Check
If you see a rectangle in a flowchart, what does it represent?
Answer
A process or a specific action that needs to be taken.
Life isn't always a straight line; sometimes we have to make choices! In a flowchart, we use a Diamond shape to represent a Decision. Inside the diamond, we ask a 'Yes/No' question. This is where the path splits into two directions. One arrow is labeled 'Yes' and the other is labeled 'No'. This allows our algorithm to handle different situations. For instance, if you are checking if you have enough money for a snack, the logic might look like: ?
How do you decide if you need an umbrella? 1. Start: Walk toward the door. 2. Decision (Diamond): Is it raining outside? 3. Path A (If Yes): Grab an umbrella Go outside. 4. Path B (If No): Just go outside. 5. End: You are outside.
Quick Check
How many arrows usually come out of a Decision (Diamond) shape?
Answer
Two arrows (usually labeled 'Yes' and 'No' or 'True' and 'False').
Sometimes, an algorithm needs to repeat a step until a goal is reached. This is called a Loop. In a flowchart, you create a loop by drawing an arrow that points backward to an earlier step. This keeps the 'flow' moving in a circle until a specific condition changes. For example, if you are eating a bowl of cereal, you keep taking a bite as long as the bowl is not empty. The logic checks: ? If 'Yes', take another bite and go back to the check!
Imagine a robot that gives high-fives: 1. Start: Set counter . 2. Process: Give a high-five. 3. Process: Add to the counter (). 4. Decision: Is ? 5. If No: Follow the arrow back to step 2. 6. If Yes: Stop.
Which shape is used to represent the very beginning of an algorithm?
If an algorithm needs to decide between two different actions, which shape should you use?
An arrow pointing back to a previous step in a flowchart creates a 'loop'.
Review Tomorrow
In 24 hours, try to draw the three main shapes (Oval, Rectangle, Diamond) and label what each one does from memory.
Practice Activity
Draw a flowchart for a simple daily task, like making a peanut butter and jelly sandwich. Make sure to include a 'Decision' diamond (e.g., 'Is the jelly jar empty?').