What Is Malloc in Data Structure?


Larry Thompson

What Is Malloc in Data Structure?

Data structures play a pivotal role in computer science and programming. They are essential for organizing and storing data efficiently.

One fundamental aspect of data structures is memory allocation, which involves allocating and deallocating memory dynamically during program execution. One popular function used for memory allocation is malloc.

What is malloc?

Malloc, short for “memory allocate,” is a function in the C programming language that allows us to dynamically allocate memory at run-time. It resides within the standard library stdlib.h.

The malloc function takes in one argument, which specifies the number of bytes of memory to be allocated.

The syntax for using malloc is as follows:

void* malloc(size_t size);

Here, the return type of malloc is void*, which means it returns a pointer to the allocated memory block. The size parameter determines the number of bytes to allocate.

It should be noted that the allocated memory block is uninitialized and may contain garbage values.

Dynamic Memory Allocation with Malloc

Dynamic memory allocation enables us to allocate memory based on our program’s specific needs at runtime. This flexibility provides significant advantages over static memory allocation, where we allocate a fixed amount of memory at compile-time.

Let’s consider an example to understand how malloc works:

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

int main() {
    int* ptr;
    int n = 5;
    ptr = (int*)malloc(n * sizeof(int));
    if (ptr == NULL) {
        printf("Memory allocation failed!");
    for (int i = 0; i < n; i++) {
        ptr[i] = i + 1;
    printf("Array elements: ");
    for (int i = 0; i < n; i++) {
        printf("%d ", ptr[i]);
    return 0;

In this example, we allocate memory dynamically using malloc to store an array of integers. The size of the array is determined by multiplying the number of elements (n) with the size of each element using the sizeof operator.

After allocating memory, we check if the allocation was successful by verifying if the pointer returned by malloc is NULL. If it is, it signifies that memory allocation failed and an appropriate action can be taken.

We then proceed to populate the allocated memory block with values in a for loop. In this case, we assign values from 1 to n.

Finally, we print the elements of the array and free the allocated memory using the free() function to release it back to the system when no longer needed. Failing to free dynamically allocated memory can lead to memory leaks and degrade program performance.


The malloc function plays a crucial role in dynamic memory allocation in data structures. It allows us to allocate memory at runtime based on our program’s specific requirements, providing flexibility and efficient use of resources.

Understanding how malloc works and utilizing it correctly is fundamental for writing efficient and robust programs.

By incorporating proper dynamic memory allocation techniques like malloc, programmers can effectively manage memory and build powerful data structures that can handle large volumes of data with ease.

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