​A little thought before you start. Having had the opportunity to teach L.C.P (to adults), I often began my courses with this remark:

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The hardest part is not learning, but changing his habits !

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And then, beware, the use of the concepts that follow, can convince and thus be used only if and only if, the following two axioms are accepted:

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     - Any collection of data constitue a set in the mathematical sense of the term.

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     - Any program is a set of data intended to cause the execution of functions.

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Thank you for agreeing with me, and JD WARNIER of course.

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However, before getting to the heart of the matter, I have to tell you the different ways of defining a set : 

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    - By understanding, ie by providing all the characteristics (or properties) that must hold any element to belong to the set.

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    - By extension, ie in doing the complete list of elements.

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I will insist on defining of a data set in understanding, for what enables us to know exactly what we are doing and what we are working on, this is the notion of such an important repository that will guide us all Along our journey in computer logic.

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Well, now let's get to work:

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Here are the steps to build a program:

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     1 °) Define the desired data at the output of the program.
     2 °) Determine the input data
     3 °) Define the structure of the program
     4 °) Write the instructions of the program
     5 °) Determine the program tests

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I do not teach anyone anything, but I have to say ...

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Let's define the output data of the program. (Logical Output File)

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