📚 Knowledge Library — Topic 7.5 — Algorithm Design & Problem Solving

Flowcharts Explained Simply

Learn how an algorithm is shown as a visual sequence using standard symbols, arrows and clear decision branches.

Start Learning Worked Example
1. Invitation

A flowchart turns an algorithm into a visual journey.

A flowchart is a diagrammatic representation of an algorithm.

Each symbol shows a different type of action, and arrows show the direction in which the algorithm moves.

💡 Key idea: a flowchart shows the sequence of steps in an algorithm.
Figure 1.1
A Visual Algorithm
Start
↓
Input
↓
Process
↓
Output
↓
Stop
2. Big Idea

Different shapes have different meanings.

Start / Stop

Terminator

Shows where the algorithm begins or ends.

Input / Output

Input / Output

Shows data entering or leaving the algorithm.

Process

Process

Shows an action or calculation.

Decision?

Decision

Asks a question with two possible outcomes.

3. FutureLogic Bridge

Think of following signs through an airport.

Airport signs guide you from check-in to security, then to the correct gate.

At some points, you make a decision: domestic or international? Gate A or Gate B?

💡 Bridge: flowchart symbols are signposts, and arrows show the route.
Figure 3.1
Follow the Route
Check-in
↓
Security
↓
Which gate?
↓
Boarding
4. Start and Stop

Every flowchart needs a clear beginning and end.

The rounded terminator symbol is used for Start and Stop.

A Start symbol normally has one arrow leaving it. A Stop symbol normally has one arrow entering it.

💡 Start begins the route. Stop ends the route.
Figure 4.1
Terminator Symbols
Start
↓
Stop
5. Input and Output

Parallelograms show data entering or leaving.

An input might ask the user to enter a number. An output might display a result or message.

The text inside the symbol should clearly state what is being input or output.

💡 INPUT receives data. OUTPUT displays data.
Figure 5.1
Input and Output
INPUT Number
↓
OUTPUT Total
6. Process

Rectangles show an action or calculation.

A process changes data or performs a task.

Examples include adding values, increasing a counter or assigning a new value to a variable.

💡 Process examples: Total ← A + B or Count ← Count + 1.
Figure 6.1
Process Symbol
Total ← Number1 + Number2
7. Decision

A diamond asks a question.

A decision has two outgoing routes, usually labelled Yes and No.

The condition inside the diamond should be a clear question that can be answered in only two ways.

🎯 Exam Tip: always label both branches. An unlabelled decision is incomplete.
Figure 7.1
Decision Branches
Is Mark ≥ 50?
Yes
OUTPUT "Pass"
No
OUTPUT "Try again"
8. Arrows and Direction

Every symbol must lead somewhere.

Arrows show the direction of flow through the algorithm.

All routes should be complete so the reader never reaches a box with nowhere to go.

💡 Trace the arrows from Start to Stop. If a route becomes stuck, the flowchart is incomplete.
Figure 8.1
Complete the Route
Symbol
↓
Arrow
↓
Next symbol
9. Computational Thinking

Flowcharts make algorithmic thinking visible.

SkillHow it appears
DecompositionEach sub-system can have its own flowchart.
Pattern recognitionRepeated decisions and loops become visible.
AbstractionOnly the steps needed for the algorithm are shown.
Algorithmic thinkingInstructions are arranged in a logical order.
💡 A flowchart is a visual plan for an algorithm.
Figure 9.1
From Thought to Flow
Break down
↓
Choose steps
↓
Arrange order
↓
Check branches
10. Worked Example

Create a flowchart to add two numbers.

The algorithm inputs two numbers, adds them and outputs the total.

Start
↓
INPUT Number1
↓
INPUT Number2
↓
Total ← Number1 + Number2
↓
OUTPUT Total
↓
Stop

Why this works

The symbols are correct, the steps follow a logical sequence and every arrow leads to the next action.

Model answer: “The flowchart starts, inputs two values, calculates their total, outputs the result and then stops.”
11. Exam Tip

Match each instruction to the correct symbol.

Do not choose a symbol because it looks suitable. Choose it because its purpose matches the instruction.

🎯 Quick check: Start/Stop = terminator, INPUT/OUTPUT = parallelogram, calculation = rectangle, question = diamond.
Figure 11.1
Symbol Matching
Begin/end → rounded
Data → slanted
Action → rectangle
Question → diamond
12. Common Mistake

Do not confuse a flowchart with a structure diagram.

A structure diagram shows how a system is divided into parts.

A flowchart shows the order in which an algorithm follows its steps.

⚠️ Common Mistake: using hierarchy boxes when the question asks for sequence and decisions.
Figure 12.1
Parts vs Steps
Structure diagram
= system parts

Flowchart
= algorithm steps
13. Summary

Flowcharts in one screen.

A flowchart represents an algorithm using standard symbols and arrows.

Terminators show Start and Stop, parallelograms show input and output, rectangles show processes and diamonds show decisions.

Decision branches must be labelled, and every route must lead somewhere.

💡 Final thought: symbols show the action; arrows show what happens next.
Figure 13.1
Final Model
Start
↓
Input
↓
Process / Decide
↓
Output
↓
Stop