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STRUCTURED DESIGN

Part 2ýPutting Theory into Practice
by George Martin

Start ý Digging In ý Making Changes ý Try It Out ý Sources and PDF

As I stated last month, using Nassi Schneiderman flowcharts helps me develop a more structured design. And, I find that the more a design is structured, the more manageable it becomes.

I hope you had a chance to look at the references from Part 1. If you did, you probably noticed that I left out case, or switch, constructions. I thought it would be too much to include, as I already had enough to cover. But when I started writing the second part of this series, wouldnýt you know that one of the first constructs I needed was best shown as a case construction. So, allow me to back up a little and cover the case and switch constructs.

Depending on a value of a variable, different tasks may need to be performed. Letýs say that the keyboardýs input of 0 to 9 is to perform 10 different functions. Listing 1 is an example of what you could code until all the cases are covered.

Most languages have a switch or case statement. And in C, it goes something like what you see in Listing 2.

The Nassi Schneiderman construction can be seen in Figure 1.

Figure 1ýHere you can see the switch, or case, construction set up as a Nassi Schneiderman chart.

I only diagrammed the 0, 1, and 2 processes and added a default process. But, you can see that this construction has only one input and one output. And depending on the switch variable, only one set of processes are followed.

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