Draw a flowchart from pseudocode

9.2 Algorithms – From Pseudocode to Flowchart

What is a Flowchart?

A flowchart is a visual diagram that shows the steps of an algorithm using standard symbols. Think of it as a recipe card for a computer: each symbol is a cooking step, and the arrows tell you the order.

  • 🟢 Oval – Start or End
  • 🔲 Rectangle – Process (e.g., “Add 1 to counter”)
  • 🔺 Diamond – Decision (e.g., “Is counter < 10?”)
  • ➡️ Arrow – Flow of control

Step‑by‑Step: Turning Pseudocode into a Flowchart

  1. Identify the start point. In pseudocode, this is usually the first line. Draw an oval and label it “Start”.
  2. Translate each line.
    • Assignments or calculations → rectangle
    • Loops (e.g., while, for) → diamond for the condition, then rectangle for the loop body, and an arrow back to the diamond.
    • Conditional branches → diamond with two arrows: one for true, one for false.
  3. Connect the symbols. Use arrows to show the direction of execution. Make sure there are no dead ends.
  4. Mark the end. After the last line of pseudocode, draw an oval labeled “End”.
  5. Check for clarity. Each symbol should be labeled clearly, and the flow should read naturally from left to right or top to bottom.

Example: A Simple Increment Loop

Consider the following pseudocode:

START
  counter ← 0
  WHILE counter < 5 DO
    counter ← counter + 1
  END WHILE
END
Pseudocode Line Flowchart Symbol Description
START Oval Indicates the beginning.
counter ← 0 Rectangle Initialise counter.
WHILE counter < 5 DO Diamond Decision: is counter less than 5?
counter ← counter + 1 Rectangle Increment counter.
END WHILE Arrow back to Diamond Loop back to decision.
END Oval End of algorithm.

Exam Tips for Flowchart Questions

  • 📝 Read the pseudocode carefully. Look for loops, conditions, and assignments.
  • 🔍 Identify the flowchart symbols. Remember the mapping: oval = start/end, rectangle = process, diamond = decision.
  • ➡️ Draw arrows correctly. They should point from one symbol to the next, showing the order of execution.
  • ⚠️ Check for missing branches. A diamond must have two arrows: one for true and one for false.
  • 📐 Keep it neat. Use straight lines and avoid crossing arrows where possible.
  • 🧠 Use analogies. Think of the algorithm as a recipe; each step is a cooking action.

Quick Recap

To convert pseudocode into a flowchart:

  1. Start with an oval labelled “Start”.
  2. Translate each line to the appropriate symbol.
  3. Connect symbols with arrows.
  4. End with an oval labelled “End”.
  5. Review for clarity and completeness.

Remember: a good flowchart is like a clear map – it shows the way from the beginning to the finish without any detours. Happy diagramming! 🚀

Revision

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