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Interpreting Flow Charts
An Example
- Here is a simple example for a thermostat and a heater.
- Turning things on or off is an OUTPUT.
- A time delay is a process.
- Note the Loop. This is where part of the flow chart gets repeated because the arrows jump back to an earlier step in the chart.
![Flow chart example.GIF](Flow_chart_example.GIF)
The Symbols
The main flow chart symbols are ...
- ellipses for the start and end points of the flow chart
- boxes to represent processes (do something)
- diamonds to represent questions, usually with a yes/no answer
- small labelled circles to join the pages of multi-page flow charts
- slanty boxes for inputs and outputs
An Example
- Flow charts are very useful for describing a sequence of steps, possibly also involving simple decisions and actions.
- Microcontroller code can be much easier to produce if a flow chart is available as a guide.
- Flow charts are used to represent inputs, processes, decisions and outputs.
- Here is a humorous example, with some incorrect symbols, from an unknown source.
- Computer programs are often documented with flow charts. The code is hard to follow but a diagram gives a clear visual overview of what the program does.
- Flow charts are usually read left to right and top down, like normal Roman text.
- Flow lines should be labelled with arrows. This is especially important if the arrow is going up or right to left.
Common Mistakes
- Forgetting to label the boxes
- Forgetting to put direction arrows on the links
- Forgetting the yes/no labels on decision boxes
- Yes there is a missing arrow in the diagram above!
A Bit of Fun
![Flow charts xkcd.GIF](Flow_charts_xkcd.GIF)
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