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The first term I want to define, is failure.

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A failure is an observable incorrect behavior of the software.

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It is conceptually related to the behavior of the

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program, rather than its code. The second term I want

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to introduce is fault, which is also called bug.

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And the fault or bug, is an incorrect piece of

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code. In other words, a fault is related to

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the code. And is a necessary, but not sufficient condition

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for the occurrence of a failure. The final

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term I want to introduce is, error. Where an

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error is the cause of a fault. It is

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usually a human error, which can be conceptual. A

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typo or something along those lines. And know that

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this terminology, failure, fault and error, is the official

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[UNKNOWN] terminology. So you cannot go wrong if you

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use it. Now, let me illustrate the difference between

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failure, fault and error. Using a small example. What I'm showing here is

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a small function that, as you can see from its name, takes an

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integer parameter i. And is supposed to double the value of i, and

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return it. As we can clearly see, this is not what the function does.