Flowcharting    

How to draw a flowchart

There are no hard and fast rules for constructing flowcharts, but there are guidelines which are useful to bear in mind.
Here are six steps which can be used as a guide for completing flowcharts.

1. describe the process to be charted (this is a one-line statement such as, "How to fill the car's petrol tank")
2. start with a 'trigger' event
3. note each successive action concisely and clearly
4. go with the main flow (put extra detail in other charts)
5. make cross references to supporting information
6. follow the process through to a useful conclusion (end at a 'target' point)

The best way to illustrate the use of these guidelines is to look at a simple example (see below) and follow how each step has been applied.

1. The first step is to identify the process to be flowcharted and to give the chart a title. In this case, it is `How to fill the car's petrol tank'.
2. Begin to draw the chart by first describing the event which initiates the process (the 'trigger'). In the example this is `Low petrol warning light comes on'.
3. Then note down each successive action taken. Actions should be described in as few words as possible, but make sure the description is not ambiguous or unclear.
4. When you reach a point at which the flowchart branches into a number of alternatives, and the resulting complexity threatens to overwhelm the exercise, choose the most important alternative to continue flowcharting with. The others can simply be terminated and dealt with in separate flowcharts. Such a point is illustrated in the example where a decision is required on how much petrol is to be put in the tank.
5. Often you may need to make cross-references to important supporting information (in this example cross references may be made to, say, a table of preferred brands of petrol, or to a list of cars able to use unleaded petrol).
6. Continue describing each event, action or decision as it occurs in sequence, until the process is concluded. In the example, this point is reached when the petrol is paid for, the tank is recharged, and you are ready to drive off.

Flowcharts help to identify all the key tasks involved and the finished chart can be used,

• as a springboard for further discussion of the process
• to connect with other flowcharts explaining related activities
• to identify points where data can be usefully collected and analysed
• to isolate possible problem areas
• to communicate the process to those unfamiliar with it

A set of useful standard symbols

It is not strictly necessary to use boxes, circles, diamonds or other such symbols to construct a flowchart, but these do help to describe the types of events in the chart more clearly. Described below are a set of standard symbols which are applicable to most situations without being overly complex.

Rounded box - use it to represent an event which occurs automatically. Such an event will trigger a subsequent action, for example `receive telephone call’, or describe a new state of affairs.

Rectangle or box - use it to represent an event which is controlled within the process. Typically this will be a step or action which is taken. In most flowcharts this will be the most frequently used symbol.

Diamond - use it to represent a decision point in the process. Typically, the statement in the symbol will require a `yes' or `no' response and branch to different parts of the flowchart accordingly.

Circle - use it to represent a point at which the flowchart connects with another process. The name or reference for the other process should appear within the symbol.