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Basic concept of algorithm
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An **algorithm** is a set of unambiguous simple instructions. It ends after a finite amount of operations and produces a result from input data.
The algorithm is designed to be executed by the processor. If the processor is a computer, then the algorithm is traduced in a programming language (ie. C/C++, Python, Fortran, Java, etc.) and becomes a **program**.

The developpement of a programm is following different steps and actors.

.. _Fig:chap3:program:

.. figure:: ./_static/fig/chap3/program.jpg
  :scale: 50%
  :align: center

  Main steps of program development

The analyse step consists on proposing a solution to the problem by writting an algorithm together with a set of verification tests proving the algorithm value.

Simple algorithm example
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Recipe of a chocolate cake is an algorithm as it includes a list of simple instructions that takes ingredients in input and produces a chocolate cake as result:

1. Preheat oven at 180°C.
2. Melt chocolate and butter together.
3. Whisk 3 eggs.
4. Add chestnut cream and beat with eggs.
5. Incorporate melt chocolate.
6. Bake for 35 min at 180°C.

Flowchart representation of an algorithm
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Algorithms can be more complex than the preceding recipe. For example it can contains structured instructions. In that case, it can be usefull to represent the algorithm using a flowchart.

.. _Fig:chap3:algoLesson:

.. figure:: ./_static/fig/chap3/algoLesson.jpg
  :scale: 60%
  :align: center

  A basic algorithm example with conditional instructions.