The term computing is a neologism proposed in 1962 by Philippe Dreyfus to characterize the automatic processing of information. So, IT deals with two complementary aspects: the immaterial programs (software, software) which describe a processing to be carried out and the machines (hardware, hardware) which execute this processing. The objective of this course is to teach you to design an ordered sequence of instructions which indicates the procedure to follow for to solve a series of equivalent problems, as well as to characterize their validity, their robustness, their reusability, their complexity or their efficiency in a programming language understandable by the computer. As Abelson et al. said, each computer program is a model, forged by the mind, of a real or imaginary process. These processes, which arise from human experience and thought, are innumerable and complex in their details. At any time, they can only be partially understood. They are rarely modeled in a satisfactory way in our computer programs. Although our programs are sets symbols carefully carved, mosaics of intertwined functions, they never stop evolving. We modify them as our perception of the model deepens, expands and generalizes, until reaching a metastable equilibrium at the borders of another possible modeling of the problem. The joyful intoxication that accompanies computer programming comes from the continual back and forth between the human mind and the computer, the mechanisms expressed by programs and the explosion of new visions that they bring. If art translates our dreams, the computer realizes them in the form of programs.