21. dynamic allocation 4.free().txt

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

int main() {
    int *ptr1, *ptr2, *ptr3, *ptr4;
    int n = 5;
    
    // allocate memory using malloc()
    ptr1 = (int*)malloc(n * sizeof(int));
    if (ptr1 == NULL) {
        printf("Memory allocation failed");
        exit(1);
    }
    printf("Memory allocated using malloc(): %p\n", ptr1);
    
    // allocate memory using calloc()
    ptr2 = (int*)calloc(n, sizeof(int));
    if (ptr2 == NULL) {
        printf("Memory allocation failed");
        exit(1);
    }
    printf("Memory allocated using calloc(): %p\n", ptr2);
    
    // reallocate memory using realloc()
    n = 10;
    ptr3 = (int*)realloc(ptr1, n * sizeof(int));
    if (ptr3 == NULL) {
        printf("Memory reallocation failed");
        exit(1);
    }
    printf("Memory reallocated using realloc(): %p\n", ptr3);
    
    // free memory using free()
    free(ptr2);
    printf("Memory freed using free()\n");
    
    // set pointer to NULL after freeing memory
    ptr2 = NULL;
    
    return 0;
}