System flowcharts are a way of displaying how data flows in a system and how decisions are made to control events.
To illustrate this, symbols are used. They are connected together to show what happens to data and where it goes. The basic ones include:
1 Symbols used in flow charts
Note that system flow charts are very similar to data flow charts. Data flow charts do not include decisions, they just show the path that data takes, where it is held, processed, and then output.
Using system flowchart ideas in this system flowchart is a diagram for a 'cruise control' for a car. The cruise control keeps the car at a steady speed that has been set by the driver.
The flowchart shows what the outcome is if the car is going too fast or too slow. The system is designed to add fuel, or take it away and so keep the car's speed constant. The output (the car's new speed) is then fed back into the system via the speed sensor.
Other examples of uses for system diagrams include:
automatic washing machines
booking systems for airlines
2 Input and output
For the system to work there is an input and an output. The process is taking the input and doing something with it - modifying it in some way - and producing an output.
In a computer system the processing will be done by a microprocessor of some kind.
Feedback is the output fed back to the input. The cruise control flowchart is an example of negative feedback because the speed is always kept at the same value. Positive feedback would push the speed away from the desired value.
Examples of inputs
Examples of outputs