What is the difference between malloc & calloc in c?

Understanding malloc and calloc in C

Introduction

When programming in C, memory allocation is a crucial aspect. Two commonly used functions for dynamic memory allocation are malloc and calloc. They serve similar purposes but have some important differences. This article will explore the distinctions between malloc and calloc to help you make informed decisions when allocating memory in your C programs.

1. malloc Function

Definition:

malloc stands for memory allocation. It is a library function in C used for dynamic memory allocation. It allocates a block of specified size and returns a pointer of type void to the beginning of the block.

Syntax:

void* malloc(size_t size);

Key Points:

• malloc allocates uninitialized memory. The content of the block is not guaranteed to be zero.
• It returns a void pointer which can be cast to any data type.
• If the allocation is successful, it returns a pointer to the allocated memory. If it fails, it returns NULL.

2. calloc Function

Definition:

calloc stands for clear allocation. Like malloc, it is used for dynamic memory allocation. However, calloc also initializes the allocated memory block to zero.

Syntax:

void* calloc(size_t num, size_t size);

Key Points:

• calloc allocates a block of memory for an array of elements, num in total, each of size bytes long.
• It initializes the allocated memory with zero.
• Similar to malloc, it returns a void pointer that can be cast to any data type.
• If the allocation is successful, it returns a pointer to the allocated memory. If it fails, it returns NULL.

3. Differences between malloc and calloc

Initialization:

• malloc: Allocates uninitialized memory.
• calloc: Allocates and initializes memory to zero.

Parameters:

• malloc: Takes a single argument - the size in bytes of the memory block to be allocated.
• calloc: Takes two arguments - the number of elements to allocate space for (num) and the size in bytes of each element (size).

Performance:

• calloc might be slightly slower due to the additional step of initializing memory.

Use Case:

• malloc is commonly used when you don't require the memory to be initialized to zero, or when you plan to change the contents of the allocated memory before using it.
• calloc is used when you want the allocated memory to be initialized to zero, for example, when dealing with arrays and you want them to start with all elements set to zero.

Short Note: In other words, we can say There is two basic difference between them.

First:

• malloc() takes a single argument(memory required in bytes),
• calloc() needs 2 arguments(number of variables to allocate memory, size in bytes of a single variable).

Second 

• malloc() does not initialize the memory allocated,
• calloc() initializes the allocated memory to ZERO

Malloc will not create the memory malloc will reserve the memory

Conclusion

Both malloc and calloc are crucial tools for dynamic memory allocation in C. Choosing between them depends on your specific requirements. Understanding their differences will help you make informed decisions, ensuring efficient memory allocation in your programs.