Code360 powered by Coding Ninjas X Naukri.com. Code360 powered by Coding Ninjas X Naukri.com
Last Updated: Jul 4, 2024
Difficulty: Easy

Difference Between malloc() and calloc()

Leveraging ChatGPT - GenAI as a Microsoft Data Expert
Speaker
Prerita Agarwal
Data Specialist @
23 Jul, 2024 @ 01:30 PM

Introduction

malloc() and calloc() are C library functions used for dynamic memory allocation. malloc() allocates uninitialized memory, while calloc() allocates zero-initialized memory. malloc() takes a single argument for the total memory size, whereas calloc() requires two arguments: the number of elements and the size of each element.

Difference between malloc and calloc

In this article, we will discuss what dynamic memory allocation is, the difference between malloc and calloc, their examples and. How these two functions are used for memory allocation.

Also See, loop and while loop

Key Differences between Malloc and Calloc

Initialization

  • malloc(): Allocates memory but does not initialize it. The allocated memory contains garbage values.
  • calloc(): Allocates memory and initializes all bytes to zero.

Parameters

  • malloc(): Takes a single argument specifying the total number of bytes to allocate.
  • calloc(): Takes two arguments: the number of elements and the size of each element.

Syntax

  • malloc(): ptr = (int*) malloc(num * sizeof(int));
  • calloc(): ptr = (int*) calloc(num, sizeof(int));

Performance

  • malloc(): Generally faster because it doesn't initialize the memory.
  • calloc(): Might be slightly slower due to zero-initialization of memory.

Use Case

  • malloc(): Preferred when you don't need the memory to be initialized, and you will be setting values yourself.
  • calloc(): Preferred when you need the memory to start with all zeroes, useful for arrays and structures.
Get the tech career you deserve, faster!
Connect with our expert counsellors to understand how to hack your way to success
User rating 4.7/5
1:1 doubt support
95% placement record
Akash Pal
Senior Software Engineer
326% Hike After Job Bootcamp
Himanshu Gusain
Programmer Analyst
32 LPA After Job Bootcamp
After Job
Bootcamp

What is Dynamic Memory Allocation?

Dynamic memory allocation is a crucial concept in computer programming and memory management. It refers to the process of assigning and managing memory during a program's runtime. Unlike static memory allocation, where memory is allocated at compile-time and remains fixed, dynamic memory allocation allows programs to allocate and release memory as needed while the program is running. Memory must be manually deallocated using the free function to avoid memory leaks. Dynamic memory is typically allocated on the heap. It provides more flexibility in managing memory during program execution.

What is malloc()?

This function is used for allocating a single large memory block according to a specific size. The 'malloc' function accepts a single argument, that is, the number of bytes of memory we want to allocate. 

The malloc() returns a pointer of type void. It can be cast into a pointer of any form. The malloc() function doesn’t initialize memory at execution time, and its contents are undefined. It has each block that contains a default garbage value initially. The allocation fails if the space is insufficient and returns a NULL pointer.

Syntax of malloc()

(castType*)  malloc(byteSize);

Parameters

The malloc function takes one parameter, size; It specifies the number of bytes to be allocated. This gives you the size of the memory block to be allocated. It must be a non-negative number.

If the requested memory allocation fails (i.e., there is not enough memory available), malloc returns a null pointer.

What is calloc()?

This function, also known as “contiguous allocation,” is used for dynamic memory allocation according to the specified number of blocks of memory of a specific type. 

The ‘calloc()’ function accepts two arguments: the number of elements for memory allocation and the size of each component. It is almost similar to the malloc() function but is different in the following ways:

  • calloc() function initializes each block with a default value of ‘0’.
     
  • It takes in two parameters or arguments.
     

The allocation fails if the space is insufficient and returns a NULL pointer.

Syntax of calloc()

NinjaPtr = (castType*)calloc(n, size);

Parameters

The calloc function takes two parameters:

  • num: It represents the number of elements to be allocated. It must be a non-negative number.
     
  • size: It specifies the size of each element in bytes. sizeof() operator is commonly used to find the size of the element.
     

The total amount of memory allocated by calloc is calculated by multiplying num and size. It then returns a pointer to the allocated memory block.


Also see, Floyd's Triangle in C

Difference between malloc() and calloc()

Below is the difference between malloc and calloc functions.

Parametersmalloc()calloc()
Number of argumentsMalloc accepts single argument (size of a memory block for allocation).Calloc accepts two arguments (number of elements for allocation, size of each element).
Return valueIn malloc, the return value is a pointer to the first byte in the allocated block of memory.In calloc, the return value is a pointer to the first byte in the allocated block of memory.
Memory allocationMalloc allocates only the requested memory block of memory.Calloc allocates memory according to the specified number of blocks of memory of a specific type.
Memory initializationIn malloc, the memory block is uninitialized and contains garbage values.In calloc, the memory block is initialized with zero.
Time efficiencyMalloc() has high time efficiency.Calloc() has low time efficiency.
SpeedMalloc() is faster than calloc().Due to the initialization step, calloc() is slower than malloc().
SyntaxSyntax: void* malloc(size_t size);Syntax: void* calloc(size_t num, size_t size);
Memory Initialization to ZeroMalloc() doesn't initialize memory to zero.Calloc() initializes memory to zero.

Why Use Malloc()?

The malloc() in C is used for: 

  • Dynamic Memory Allocation: malloc() is commonly used for dynamic memory allocation. It allows the programmer to allocate memory during program execution rather than at compile time.
  • Flexibility: malloc() provides flexibility in allocating memory blocks of varying sizes based on program requirements.
  • Efficiency: Since malloc() does not initialize the allocated memory block, it can be more efficient in terms of performance and memory usage, especially when large blocks of memory need to be allocated.
  • Custom Initialization: malloc() allows the programmer to customize the initialization of memory blocks if required. It doesn't automatically initialize memory to zero, which can be advantageous in certain situations where initialization is not necessary or can be done explicitly.
  • Common Usage: malloc() is widely used in C and C++ programming, and many libraries and codebases rely on it for dynamic memory allocation.

Why Use Calloc()?

The calloc() in C is used for: 

  • Initialization to Zero: One of the primary reasons to use calloc() is its ability to initialize the allocated memory block to zero by default. This can be crucial for ensuring predictable behavior, especially when dealing with data structures or arrays.
  • Array Initialization: calloc() is commonly used when allocating memory for arrays or data structures that need to be initialized to zero. This simplifies code and reduces the risk of using uninitialized memory.
  • Allocation of Zeroed Memory: In scenarios where zeroed memory is required, such as initializing buffers for I/O operations or security-sensitive data handling, calloc() provides a convenient and efficient way to allocate and initialize memory in a single step.
  • Safety and Reliability: By initializing memory to zero, calloc() helps prevent potential bugs and security vulnerabilities that may arise from using uninitialized memory.
  • Ease of Use: For programmers who require zero-initialized memory, calloc() offers a straightforward and convenient solution without the need for additional initialization steps.

Example of malloc() in C

Let's see an example of malloc() in C.

Implementation in C

  • C

C

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

int main() {
int *arr;
int n = 5;

// Allocate memory for an array of integers
arr = (int *)malloc(n * sizeof(int));

// Initialize the array
for (int i = 0; i < n; i++) {
arr[i] = i+1;
}

// Print the array elements
for (int i = 0; i < n; i++) {
printf("%d ", arr[i]);
}

// Free the allocated memory
free(arr);
return 0;
}

Output

output

Example of calloc() in C

Let's see an example of calloc() in C.

Implementation in C

  • C

C

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

int main() {
int *arr;
int n = 5;

// Allocate and initialize memory for an array of integers
arr = (int *)calloc(n, sizeof(int));

// Initialize the array
for (int i = 0; i < n; i++) {
arr[i] = i+1;
}

// Print the array elements
for (int i = 0; i < n; i++) {
printf("%d ", arr[i]);
}

// Free the allocated memory
free(arr);
return 0;
}

Output

output

Also read - Bit stuffing program in c

Frequently Asked Questions

What does malloc () calloc () realloc () free () do?

malloc() allocates uninitialized memory, calloc() allocates zero-initialized memory, realloc() resizes previously allocated memory, and free() deallocates allocated memory.

Why use realloc instead of malloc?

realloc() resizes existing memory without losing its content, while malloc() allocates new memory, requiring manual data transfer from the old block.

Is calloc() slower than malloc()?

calloc() is generally slower than malloc(), as we need to initialize the allocated memory to zero.

What is the difference between malloc calloc and new delete?

Malloc and calloc are C functions that dynamically allocate memory, whereas new and delete are C++ operators that do the same thing. The main difference is that new and delete calls constructors and destructors automatically, but malloc and calloc do not.

What is the syntax of malloc and calloc?

The syntax of malloc and calloc are: 

For malloc() : (castType*) malloc(byteSize);

For calloc() : NinjaPtr = (castType*)calloc(n, size);

and the return value of both malloc and calloc is a pointer to the first byte in the allocated block of memory.

Conclusion

We hope this article helped you understand the difference between malloc and calloc. We have also discussed how these two functions are used for memory allocation. Refer to our other articles to better understand memory allocation.

You will find straightforward explanations of almost every topic on this platform. You can read more such articles on our platform, Code360.

Topics covered
1.
Introduction
2.
Key Differences between Malloc and Calloc
2.1.
Initialization
2.2.
Parameters
2.3.
Syntax
2.4.
Performance
2.5.
Use Case
3.
What is Dynamic Memory Allocation?
4.
What is malloc()?
4.1.
Syntax of malloc()
4.2.
Parameters
5.
What is calloc()?
5.1.
Syntax of calloc()
5.2.
Parameters
6.
Difference between malloc() and calloc()
7.
Why Use Malloc()?
8.
Why Use Calloc()?
9.
Example of malloc() in C
9.1.
Implementation in C
9.2.
C
9.3.
Output
10.
Example of calloc() in C
10.1.
Implementation in C
10.2.
C
10.3.
Output
11.
Frequently Asked Questions
11.1.
What does malloc () calloc () realloc () free () do?
11.2.
Why use realloc instead of malloc?
11.3.
Is calloc() slower than malloc()?
11.4.
What is the difference between malloc calloc and new delete?
11.5.
What is the syntax of malloc and calloc?
12.
Conclusion