THE SYMBOLS
Rectangles and diamonds
The two most common boxes are the processing step, drawn as a rectangle, and the decision, drawn as a diamond with a yes/no question inside.
Learn the symbolsWHAT THE STANDARDS SAY
Box, diamond,
arrow.
A flowchart is a recipe drawn as shapes.
ONE STEP per box
1921 First structured flow process chart presented
- Rectangle: do
- Diamond: decide
- Arrow: what next
- Flowcharts in three lines
Flowcharts show the steps of a process as boxes joined by arrows. Different shapes mean different kinds of step, and those shapes have been written into standards, from engineering in the 1940s to computing today.
THE SHORT ANSWER
Two shapes
do most of the work.
Processing steps and decisions are the most common boxes.
Arrows show the order.
THE HISTORY
From factory floors
The first structured method, the flow process chart, was presented to the American Society of Mechanical Engineers in 1921, to document how work flowed.
See the dates
IN SCHOOL
Six symbols for GCSE
OCR's GCSE Computer Science specification lists six flowchart symbols: line, process, decision, input/output, sub program and terminal.
Draw one wellA QUICK SYMBOL CHECK
What does
this shape mean?
Pick a shape to see what it usually stands for in a flowchart. The bar shows how widely the symbol is used.
Shapes as described in the New World Encyclopedia's account of typical computer science flowcharts. Different flowchart types have their own conventions.
FOUR HABITS FOR CLEAR FLOWCHARTS
Clear shapes,
labelled arrows.
These habits follow the conventions described for typical flowcharts and what GCSE specifications expect.
Start and end with a terminal
Use an oval or rounded rectangle marked Start and End, so the reader knows where to begin.
One action per rectangle
Keep each processing step to a single clear action, written as a short instruction.
Label every decision arrow
A decision has two arrows out, one for yes or true and one for no or false. Always label them.
Break up complex decisions
More than two arrows out of a decision is a sign it should be broken down further, or replaced with a pre-defined process.
TWO DATES WORTH KNOWING
Engineers drew them first,
standards followed.
One date for the first process chart,
one for the international standard still in use.
1921
First structured flow process chart presented
The flow process chart was introduced to members of the American Society of Mechanical Engineers. In 1947 ASME adopted a symbol set derived from it as a standard for process charts.
ORIGIN · ASME
1985
International flowchart symbols standard published
ISO 5807 defines symbols for data, program and system flowcharts. It replaced two 1973 standards and was last reviewed and confirmed in 2019, so it remains current.
STANDARD · ISO 5807
Flowcharts used to be a popular way to describe computer algorithms. Their popularity fell in the 1970s, when interactive terminals and newer programming languages let algorithms be written more concisely as code.
WHERE FLOWCHARTS ARE USED
From quality control
to computing class.
Flowcharts are used to design and document processes in many fields. They help readers see what is going on and spot flaws or bottlenecks, and they are counted among the seven basic tools of quality control.
In schools, BBC Bitesize describes a flow diagram as a set of instructions drawn with standard symbols, and the AQA GCSE specification asks students to represent algorithms using pseudo-code, program code and flowcharts.
Questions
Questions people ask
What does a diamond mean in a flowchart?
A decision, usually a yes/no or true/false question. It typically has two arrows coming out, one for each answer, and the arrows should always be labelled.
What shape is used for start and end?
An oval, lozenge or rounded rectangle, usually containing the word Start or End. OCR calls this the terminal symbol.
What is the parallelogram for?
Input or output, such as getting a value from the user or displaying a result.
Is there an official flowchart standard?
Yes. ISO 5807, published in 1985, sets documentation symbols and conventions for data, program and system flowcharts. It was last reviewed and confirmed in 2019.
Which flowchart symbols do GCSE students learn?
OCR's J277 Computer Science specification lists line, process, decision, input/output, sub program and terminal. AQA expects students to represent algorithms as flowcharts as well as pseudo-code and program code.
Where the facts come from
Updated