Flow charts

One way of representing algorithms is to use flow charts, also called flow diagrams. They are a useful way of planning how a computer program might work, and show others your thinking.

A flow chart shows the key points in an algorithm:

  • the start and end
  • the order in which the sequences of instructions are performed
  • the points where inputs and outputs occur
  • the points where decisions are made about what to do next

A sequence of many instructions that does not involve any of these key points may be represented as a single rectangular box.

Flow charts use a variety of standard flow chart symbols to represent different elements, and arrows to show the flow or direction. These shapes are formally agreed standards (British Standard BS4058). The most commonly used symbols are:

  • start or stop (end)
  • input/output
  • decision
  • process
Flowchart key detailing the different shapes and their meanings