Dynamic Memory Allocation in C

📌 What is Dynamic Memory Allocation?

Dynamic Memory Allocation is the process of allocating memory at runtime using pointers. Unlike static memory allocation, dynamic memory allows the program to request memory from the heap during execution.

🧰 Why Use It?

• When the size of data is not known at compile-time
• To allocate memory for complex structures like arrays, linked lists, etc.
• To free memory when it's no longer needed

📚 Functions Used

• malloc() – Allocates a single block of memory
• calloc() – Allocates and initializes multiple blocks
• realloc() – Reallocates memory to change its size
• free() – Frees dynamically allocated memory

💡 Example Code

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

int main() {
    int *ptr;
    int n;

    printf("Enter number of elements: ");
    scanf("%d", &n);

    // Allocate memory using malloc
    ptr = (int*) malloc(n * sizeof(int));

    // Check if memory is allocated
    if (ptr == NULL) {
        printf("Memory allocation failed!");
        return 1;
    }

    // Use the memory
    for (int i = 0; i < n; i++) {
        ptr[i] = i + 1;
    }

    printf("Elements: ");
    for (int i = 0; i < n; i++) {
        printf("%d ", ptr[i]);
    }

    // Free the memory
    free(ptr);

    return 0;
}
    

📝 Explanation

• malloc(n * sizeof(int)) → allocates memory for n integers.
• ptr[i] → accesses the dynamically allocated array.
• free(ptr) → releases the memory to prevent memory leaks.

⚠️ Tips

• Always check if the pointer returned by malloc() or calloc() is NULL.
• Don’t forget to free the memory after use.
• Accessing memory after freeing it causes undefined behavior.