How do dynamic memory allocation functions (malloc, calloc, realloc, free) operate in C?

Explanation & Concept

• `malloc(bytes)`: Allocates uninitialized memory on the heap. • `calloc(n, size)`: Allocates memory and zeroes out all bytes. • `realloc(ptr, new_size)`: Resizes an existing heap allocation. • `free(ptr)`: Releases allocated memory back to the heap manager.

Code Example

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

int main() {
    int n = 5;
    int *arr = (int *)malloc(n * sizeof(int));
    
    if (arr == NULL) {
        fprintf(stderr, "Memory allocation failed\n");
        return 1;
    }

    for (int i = 0; i < n; i++) arr[i] = i * 10;
    
    free(arr);   // Prevent memory leak
    arr = NULL;  // Prevent dangling pointer use
    return 0;
}

How It Works & Key Takeaways

Always check for `NULL` after `malloc`, and set freed pointers to `NULL` to avoid dangerous use-after-free bugs.

Mock Test · 1 Questions · Optional

Ready for File I/O?

Take a quick test to evaluate yourself, or move straight to the next module.

Intermediate3 questions

Skip

Dynamic Memory AllocationBeginner

1Question 1 of 1

How do dynamic memory allocation functions (malloc, calloc, realloc, free) operate in C?

Explanation & Concept

Code Example

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

int main() {
    int n = 5;
    int *arr = (int *)malloc(n * sizeof(int));
    
    if (arr == NULL) {
        fprintf(stderr, "Memory allocation failed\n");
        return 1;
    }

    for (int i = 0; i < n; i++) arr[i] = i * 10;
    
    free(arr);   // Prevent memory leak
    arr = NULL;  // Prevent dangling pointer use
    return 0;
}

How It Works & Key Takeaways

Always check for `NULL` after `malloc`, and set freed pointers to `NULL` to avoid dangerous use-after-free bugs.

Mock Test · 1 Questions · Optional

Ready for File I/O?

Take a quick test to evaluate yourself, or move straight to the next module.

Intermediate3 questions

Skip