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C++ memset() function | Is Memset Faster than Calloc?

  • Nov 06, 2023
  • 6 Minute Read
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  • By Abrar Ahmed
C++ memset() function | Is Memset Faster than Calloc?

When working with C++, a powerful programming language, developers often seek ways to optimize their code. One such tool at their disposal is the 'memset' function. In this article, we will explore the purpose of memset in C++ and compare its performance with calloc. 

What does memset in C++ do?

The memset function in C++ allows developers to set a block of memory to a specific value. This can be particularly useful when initializing arrays, buffers, or any other data structures that occupy a contiguous chunk of memory. By assigning a specific value to each byte of the memory block, it enables efficient initialization, making it an indispensable tool for C++ programmers.

The primary use of memset is to initialize memory with a specific value. The function takes three arguments: a pointer to the starting address of the memory block, the value to be assigned, and the number of bytes to be set. Here's an example:


int main() {
int arr[5];
memset(arr, 0, sizeof(arr));
// The above line sets all elements of 'arr' to 0

// Rest of the code...
return 0;


In the example above, we include the header file to access the memset function. We create an integer array named `arr` with a size of 5. The memset function is then called, passing 'arr' as the pointer to the memory block, 0 as the value to be assigned, and 'sizeof(arr)' as the number of bytes to be set. This effectively sets all elements of `arr` to 0.

Is memset faster than calloc?

When it comes to initializing memory, both serve different purposes. While memset assigns a specific value to each byte of a memory block, calloc initializes the memory to zero.

In terms of performance, memset is generally faster than calloc because it doesn't require zeroing out the memory. However, the difference in performance might not be significant for small memory blocks. It's important to choose the appropriate function based on your specific requirements.

To use the memset function in C++, you need to include the header file. This file provides the necessary declarations and definitions for various string manipulation and memory-related functions.

In addition to arrays, it can also be used with vectors in C++. Vectors are dynamic arrays that can grow or shrink as needed. When initializing a vector with a specific value, you can employ memset in a similar manner as with arrays.

However, it's important to note that memset is not the recommended way to initialize vectors in C++. Instead, you should use the appropriate constructor or the `assign` member function provided by the vector class. These methods ensure that the vector is initialized correctly and that any necessary memory allocation is handled automatically.


Overall, memset serves as a valuable tool for initializing memory blocks with specific values. Its ability to efficiently set bytes in a memory block makes it a favored choice among programmers striving for optimal performance. Whether it's arrays or vectors, it proves to be a versatile function that enhances the efficiency and effectiveness of C++ programming.

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About The Author
Abrar Ahmed
An ambivert individual with a thirst for knowledge and passion to achieve. Striving to connect Artificial Intelligence in all aspects of life. I am also an avid coder and partake in coding challenges all the time on Leetcode and CodeChef.