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

/* Dynamic array: grow on demand */
int main(void)
{
    size_t capacity = 4;
    size_t count    = 0;
    int   *arr      = malloc(capacity * sizeof(int));
    if (!arr) { perror("malloc"); return EXIT_FAILURE; }

/* Fill beyond initial capacity to trigger realloc */
    for (int i = 0; i < 10; i++) {
        if (count == capacity) {
            capacity *= 2;
            int *tmp = realloc(arr, capacity * sizeof(int));
            if (!tmp) {
                free(arr);           /* don't leak on failure */
                perror("realloc");
                return EXIT_FAILURE;
            }
            arr = tmp;
            printf("Grew to capacity %zu
", capacity);
        }
        arr[count++] = i * i;
    }

printf("Array: ");
    for (size_t k = 0; k < count; k++)
        printf("%d ", arr[k]);
    printf("
");

/* calloc: zero-initialised */
    int *zeros = calloc(5, sizeof(int));
    if (zeros) {
        printf("calloc zeros: %d %d %d
", zeros[0], zeros[1], zeros[2]);
        free(zeros);
    }

free(arr);   /* always free what you malloc */
    return EXIT_SUCCESS;
}