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STRUCTURED DESIGN

Part 1: An Introduction to Structured Techniques
by George Martin

Start ý Sequence ý Selection ý Iteration/Looping ý Testing ý Nassi-Schneiderman Charts ý Sources and PDF

NASSI-SCHNEIDERMAN CHARTS

Now youýve got all the tools to do structured design. But, I found that by using only this flowchart technique, I didnýt produce great structured designs. It was too easy to let the implementation wander.

Then I was introduced to Nassi-Schneiderman (NS) charting. NS charts use the same structured principles I just covered, but they are drawn slightly different. I refused to use these charts in the beginning, feeling that they were too restrictive. But I soon came to realize that this was just the restriction I was looking for. [1ý3]

Imagine the entire piece of paper as the flowchart. A vertical line along the left binds the work. Horizontal lines separate sequences or processes.

Does Figure 7 look familiar? These are the three processes charted in Figure 1.

Figure 7ýProcesses A, B, and C from Figure 1 are seen here in an NS chart format.

If the condition is true, processes A and B are performed. If the condition is false, then none are performed. Figure 8 shows the selection of Figure 2.

Figure 8ýWhether the condition is true or false determines if you go on to the next process.

And, the NS charts for the while structure and until structure can be seen in Figures 9 and 10, respectively.

Figure 9ýHere you can see the NS chart for the while structure.

Figure 10ýAnd here, the until structure.

Look over these constructs and check out the web sites listed in the References section. I even included a Java program for producing NS charts on a PC.

Next month, Iýll apply these techniques to a flowchart that isn't so structured. Itýll be interesting to see what I come up with.

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