Discovering Inputs, Processes, and Outputs
Every program has inputs, processes, and outputs, whether it’s a simple program like this one or a complex application like Facebook. In fact, large applications are simply a bunch of smaller programs that communicate. The output of one program becomes the input of another.
You can ensure that both small and large programs work well if you take the time to clearly state what these inputs, processes, and outputs are. An easy way to do that, if you have a clear problem statement, is to look at the nouns and verbs in that statement. The nouns end up becoming your inputs and outputs, and the verbs will be your processes. Look at the problem statement for our tip calculator:
Create a simple tip calculator. The program should prompt for a bill amount and a tip rate. The program must compute the tip and then display both the tip and the total amount of the bill.
First, look for the nouns. Circle them if you like, or just make a list. Here’s my list:
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bill amount
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tip rate
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tip
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total amount
Now, what about the verbs?
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prompt
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compute
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display
So we know we have to prompt for inputs, do some calculations, and display some outputs. By looking at the nouns and verbs, we can get an idea of what we’re being asked to do.
Of course, the problem statement won’t always be clear. For example, the problem statement says we need to calculate the tip, but it then says we need to display the tip and the total. It’s implied that we’ll need to also add the tip to the original bill amount to get that output. And that’s one of the challenges of building software. It isn’t spelled out to you 100% of the time. But as you gain more experience, you’ll be able to fill in the gaps and read between the lines.
So with a little bit of sleuthing, we determine that our inputs, processes, and outputs for this program look like this:
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Inputs: bill amount, tip rate
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Processes: calculate the tip
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Outputs: tip amount, total amount
Are we ready to start producing some code? Not just yet.