1. The program begins by defining the maximum number of modalities that can be entered (MAX_MODALITIES is set to 20).

2. It includes necessary header files like <stdio.h>, <stdlib.h>, and <math.h> for input/output, memory allocation, and mathematical functions respectively.

3. Several functions are defined to calculate statistical elements:

   • calculerMoyenne: Calculates the mean of the input modalities.
   • calculerVariance: Calculates the variance of the input modalities.
   • calculerEcartType: Calculates the standard deviation using the variance.
   • calculerMediane: Calculates the median of the input modalities.
   • calculerMode: Calculates the mode of the input modalities.

4. In the main function:

   • An array modalites is declared to store the input modalities, and variables n and entree are initialized.
   • The program asks the user to enter the modalities using a while loop, stopping when -1 is entered or the maximum number of modalities is reached.
   • After input, the program calculates the mean, variance, standard deviation, median, and mode using the defined functions.
   • Finally, it displays the input modalities, along with the calculated statistical elements.

The program provides a simple interactive way for the user to input statistical data and then computes and displays various statistical measures based on that input.