Flowcharts

Use standard flowchart symbols to plan algorithms with steps, inputs, outputs and decisions.

About 2 min read
  • Identify standard flowchart symbols
  • Follow a flowchart step by step
  • Plan a simple algorithm using a decision
Before you start

You know that an algorithm is a set of steps that solves a problem. A flowchart is one way to show those steps.

Drawing an algorithm

A flowchart shows an algorithm as a diagram. Each shape has a meaning, and arrows show the order of the steps. Programmers often use flowcharts to plan before they write code. This helps them find mistakes early and explain their ideas to other people.

Definition: flowchart

A diagram that shows the steps of an algorithm using standard symbols.

Definition: decision

A step with a yes or no question that chooses the next path.

Standard symbols

| Symbol | Use | | --- | --- | | Oval | Start or end | | Parallelogram | Input or output | | Rectangle | Process, such as a calculation | | Diamond | Decision |

Check a password length

Plan an algorithm that says whether a password has at least 8 characters.

  1. Oval: Start.
  2. Parallelogram: Input password.
  3. Diamond: Is the length at least 8?
  4. Yes path: Output Strong enough.
  5. No path: Output Too short.
  6. Oval: End.
Every decision needs two paths

A diamond must show where to go for yes and where to go for no.

Exam focus
Say it like this“Use a diamond for the question and label its Yes and No exits.”
Not like this“Use a box for the question.” — The symbol and labels both matter.
Common mistakeForgetting to label decision paths or leaving a path with nowhere to go.

Practice

Which symbol shows a decision?
A diamond.
Which symbol shows input or output?
A parallelogram.
What do arrows show?
The order in which the steps are followed.
Going further
Plan a flowchart that inputs a mark and outputs Pass if it is at least 50, otherwise Try again.
Start, input mark, decision: is mark at least 50? Yes: output Pass. No: output Try again. Both paths reach End.

Quick check

Flowcharts quick check

Which symbol starts a flowchart?

Terminator shapes mark where the algorithm begins and where it ends.

Which step belongs in a rectangle?

This shows a process, which changes or calculates a stored value.

How many exits does a yes or no decision have?

One path handles yes and another handles no, so each case continues.
Key takeaways
  • Flowcharts show algorithms as diagrams.
  • Each symbol has a meaning.
  • Arrows show the order of steps.
  • Decisions need labelled yes and no paths.
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