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|Drawing a Structured Flowchart|
|Structures||You can make your flowcharts easier to understand and less
subject to errors by using only a fixed set of structures. These structures
Whether you are flowcharting software programs or business processes, using only these structures will make it easier to find and correct errors in your charts. Each structure has a simple flow of control with one input and one output. These structures can then be nested within each other. Any chart can be drawn using only these structures. You do not have to use GOTO or draw spaghetti diagrams just because you are drawing a flowchart. You can draw structured flowcharts.
|The Colored Edge Shapes Stencil||The samples shown below were all drawn using RFFlow. If you
don't have RFFlow installed, you can download
the free trial version. It will allow you to draw charts just like these.
Once RFFlow is installed, run RFFlow and click on the More Shapes button.
Scroll to the Flowcharting folder and click the plus sign to open it.
Click the Colored Edge Shapes stencil and then click the Add Stencil button.
To download this chart, click flowchart_structure_sequence.flo.
The flowchart above demonstrates a sequence of steps. The reader would
start at the Start shape and follow the arrows from one rectangle to the
other, finishing at the End shape. A sequence is the simplest
flowcharting construction. You do each step in order.
To download this chart, click flowchart_structure_decision.flo.
This structure is called a decision, "If Then.. Else" or a conditional. A question is asked in the decision shape. Depending on the answer the control follows either of two paths. In the chart above, if the temperature is going to be less than freezing (32 degrees Fahrenheit) the tomatoes should be covered. Most RFFlow stencils include the words "Yes" and "No" so you can just drag them onto your chart. "True" and "False" are also included in most of the flowcharting stencils.
To download this chart, click flowchart_structure_loop.flo.
This structure allows you to repeat a task over and over. The red chart above on the left does the task and repeats doing the task until the condition is true. The green chart on the right checks the condition first and does the task while the condition is true. It is not important that you remember whether the loop is a "Do While" or "Repeat Until" loop, only that you can check the condition at the start of the loop or at the end. You can also have the conditions reversed and your loop is still a structured design loop. A slight variation of the above is the "For each...do the following" loop shown below.
To download this chart, click flowchart_structure_for_loop.flo.
The above chart performs the task 10 times as X counts from 0 to 10. This is just a Repeat Until X is equal to 10, but it is so common a structure that some refer to it as the "For Loop." The names are really not important. What is important is that you use only the basic structures shown here to create a structured flowchart.
To download this chart, click flowchart_structure_case.flo.
The structure above is called the case structure or selection structure. The decision works fine if you have only two outputs, but if there are several, then using multiple decisions makes the chart too busy. Since the case structure can be constructed using the decision structure, it is superfluous, but useful. The case structure helps make a flowchart more readable and saves space on the paper.
|Other Good Design Practices|
|Start and End||
To download this chart, click flowchart_start_end.flo.
Each flowchart must have one starting point. It can have multiple ending points, but only one starting point. The same terminal shape is used for the start and end. The terminal shape is a rectangle that is semicircular on the left and right as shown above. You can use other words instead of start and end, like begin and finish, or any words with a similar meaning. Some companies use an oval instead of a terminal shape. The bottom line is that it should be clear to the person looking at the chart where the chart starts and where it ends.
|Connector Block and
Off Page Connector
To download this chart, click flowchart_off_page_connector.flo.
If you have to break up a chart, you can use a connector block symbol which
is a circle. In the chart above there is a circle with the letter
"A" at the bottom left of the chart. This signifies that control
should be transferred to another point on the chart that has a circle with the
letter "A." That point is located at the upper right corner of the
chart. Using connectors allows you to fit charts to the paper more easily. The
circle can be used to reference a point on the same page or on another page.
|Title, Key, Name, Date||
A good flowchart should have a title, either on the chart or in the text of
the document. It is sometimes helpful to include a key to the shapes, especially
if you are using any non-standard shapes. Including the name of the author and
date of last modification is also useful. These items are highlighted in the
Click on this link to download the above chart flowchart_title_key.flo.
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