Let's create a sample program that combines structures, arrays, dynamic allocation, and pointer arithmetic, along with comments for explanation:

#include <stdio.h>
#include <stdlib.h>

// Define a structure representing a point in 3D space
struct Point3D {
    float x;
    float y;
    float z;
};

int main() {
    int numPoints;

    // Get the number of points from the user
    printf("Enter the number of 3D points: ");
    scanf("%d", &numPoints);

    // Dynamically allocate an array of Point3D structures
    struct Point3D *pointsArray = (struct Point3D *)malloc(numPoints * sizeof(struct Point3D));

    // Check if memory allocation was successful
    if (pointsArray == NULL) {
        fprintf(stderr, "Memory allocation failed. Exiting...\n");
        return 1; // Exit with an error code
    }

    // Populate the array with user-inputted 3D points
    printf("Enter the coordinates for each point (x y z):\n");
    for (int i = 0; i < numPoints; ++i) {
        printf("Point %d: ", i + 1);
        scanf("%f %f %f", &(pointsArray[i].x), &(pointsArray[i].y), &(pointsArray[i].z));
    }

    // Print the entered 3D points using pointer arithmetic
    printf("\nEntered 3D points:\n");
    for (int i = 0; i < numPoints; ++i) {
        // Using pointer arithmetic to access each Point3D structure in the array
        printf("Point %d: (%.2f, %.2f, %.2f)\n", i + 1, (pointsArray + i)->x, (pointsArray + i)->y, (pointsArray + i)->z);
    }

    // Deallocate the dynamically allocated memory
    free(pointsArray);

    return 0;
}

Explanation:

1. We define a structure Point3D to represent a point in 3D space with x, y, and z coordinates.

2. The program dynamically allocates an array of Point3D structures based on user input for the number of points.

3. It prompts the user to input the coordinates for each 3D point.

4. Using pointer arithmetic, it prints the entered 3D points.

5. Finally, it deallocates the dynamically allocated memory to prevent memory leaks.

This example demonstrates the combination of structures, arrays, dynamic memory allocation, and pointer arithmetic in a simple program.