C language Example of dynamic allocation array

/*
Example: dynamic memory allocation for array in C language
*/

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <stdbool.h>
#include <errno.h>
#include <unistd.h>?

int main()
{

    // Used to save the base address of the created memory block
    int* ptr;
    int n, i;

    // Get the size of the array from the user
    printf("Please enter the number of array elements:");
    scanf("%d",&n);
    printf("The number of elements is: %d\n", n);

    // Use malloc () function to dynamically allocate memory
    ptr = (int*)malloc(n * sizeof(int));

    // Check whether malloc has successfully allocated memory
    if (ptr == NULL) {
        printf("Memory not allocated successfully.\n");
        exit(0);
    }
    else {

        printf("Memory allocated successfully.\n");

        // Set array elements
        for (i = 0; i < n; ++i) {
            ptr[i] = i + 1;
        }

        // print array elements
        printf("elements: ");
        for (i = 0; i < n; ++i) {
            printf("%d, ", ptr[i]);
        }
    }

    return 0;
}

output:

Please enter the number of array elements:8
The number of elements is: 8
Memory allocated successfully.
elements: 1, 2, 3, 4, 5, 6, 7, 8,
Process returned 0 (0x0)   execution time : 9.076 s