Difference between Malloc and Calloc

Difference between Malloc and Calloc

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Updated on Aug 29, 2023 11:12 IST

Malloc and Calloc are dynamic memory allocation methods in C language. You will learn the differences between these two. And will also see the applications of them.

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When a computer executes a program, it needs memory to store its instructions. Therefore, every computer has a memory where the data is stored. The most common way to allocate memory in a computer is by using a function called Malloc. Regular dynamic memory allocation is when you allocate new blocks of memory with the help of Malloc or calloc. This allocation is necessary when you want to create new variables or arrays dynamically. It would be best to use Malloc or calloc when you want to do dynamic memory allocation in C language for an integer, word, or heap-allocated structure. In this article you will learn about Malloc vs Calloc.

Table of contents

Difference between Malloc and Calloc

Parameter Malloc Calloc
Memory block Malloc creates a single memory block of a user-specified size.  Calloc can allocate multiple memory blocks to a variable
Initialization value The malloc function is initialized to garbage values if no value given.  Memory blocks allocated by the calloc function are always initialized to zero.
Arguments The number of arguments is 1 i.e byte_size The number of arguments is 2. Calloc is slower than malloc i.e number of memory blocks and size of memory block
Speed malloc performs faster than calloc Calloc performs slower than malloc
Time efficiency More time efficient than calloc() Less time efficient than malloc().
Return value The Malloc() function only returns the starting address, and makes it zero. Before assigning the address, the Calloc() function returns the starting address and makes it zero. 
Allocation malloc() indicates memory allocation. calloc() indicates contiguous allocation.
Memory Malloc allocates a large block of memory with a specific size Calloc allocates a specific amount of memory.
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What is Malloc? 

A malloc() stands for memory allocation. Malloc is also known as a memory allocation function. Malloc () so dynamically memory allocation of a large block of memory of the specified size. Returns a pointer of type void cast to any shape.

A malloc allocates contiguous blocks of main memory and deallocates it when no longer needed. It is invoked with a pointer to a block of memory and size as arguments. When allocated memory is required, the program’s kernel must first load it from the computer’s main memory into its available kernel space; only then can the program use it. 

Must explore: Difference between Static and Dynamic memory allocation

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Question comes to mind it does malloc allocate contiguous memory?

Yes,

malloc
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function in C/C++ allocates a block of memory of the specified size from the heap. The memory allocated by
malloc
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is indeed contiguous, which means that the allocated block of memory consists of consecutive bytes. This contiguous memory allows for efficient traversal and indexing of the allocated memory region.

The

malloc
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function returns a pointer to the first byte of the allocated memory block. By using pointer arithmetic, you can access individual bytes, elements, or structures within the allocated memory.

Syntax of Malloc ()

Here is a Syntax of Malloc ()


 
ptr = (cast_type *) malloc (byte_size);
Example: ptr = (int *) malloc (30)
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Successful execution of this statement will allocate 30 bytes of memory space. The address of the first byte of reserved memory is assigned to the pointer ‘ptr’ of type int. 

Example of Malloc

Using Malloc allows programmers to store large amounts of data in user structures without excessive disk I/O operations or physical RAM usage. Moreover, when freeing blocks of allocated memory, programmers can free blocks one at a time or entire heaps- depending on their needs.

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Application of Malloc 

A malloc library is a crucial tool for developing high-performance applications as it allows for efficient management of application memory resources. For example, using Malloc allows programmers to store large amounts of data in user structures without excessive disk I/O operations or physical RAM usage. .

What is Calloc?

Calloc() stands for contiguous allocation. It is used to allocate memory in a contiguous way. It is a particular type of library routine. The calloc() function allocates a fixed amount of memory and initializes it to zero. If you return an empty pointer to a memory location, you can cast the function to the desired type.

Calloc works differently from Malloc in that it allocates memory according to a caller’s request and returns it as a block of unfillable chunks (CUF). In other words, it allocates chunks of specific sizes instead of allocating all available memory at once. Calloc may allocate unneeded space and slower speeds if you don’t request specific sizes.

Syntax of calloc()

Here is a Syntax of Malloc ()


 
ptr = (cast_type *) calloc (n, size);
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The above syntax is used to allocate n memory blocks of equal size. All bytes are initialized to zero when space is allocated. Returns a pointer to the first byte of the currently occupied memory space.

 

Example of Calloc


 
ptr = calloc(5,4);
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The above syntax is used to allocate five memory blocks of size 4. 

 

Application of Calloc 

Calloc is helpful when efficiently allocating large blocks of memory without interfering with existing resources. For example, it’s often used in computer programming when allocating dynamic memory for variables. The calloc command can efficiently distribute resources across a group of devices.

Key differences between Malloc and Calloc

  • Dynamic mapping happens at runtime. Malloc allocates a large block of memory of a certain size, while Calloc allocates a certain amount.
  • The Malloc () and calloc() functions differ in how the functions are used when allocating memory at runtime.
  • The Malloc () function only returns the starting address, it doesn’t zero it. On the other hand, the calloc() function returns the starting address, zeroing it. 
  • The number of arguments for the malloc function is 1, but the number of arguments for the calloc function is 2.
  • Malloc() is more time efficient than calloc(), but Malloc () is less safe than calloc(), Malloc does not initialize memory, but calloc does memory initialization.

Conclusion

Malloc and calloc are commonly used to allocate memory for dynamic memory allocation. The calloc or malloc functions are used for dynamic memory allocation in the C programming language. The main difference between malloc() and calloc() is that calloc() always takes two arguments and malloc() only takes one. If you liked this article then do like and share.

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Related reads:

Malloc in C Programming: How to Allocate Memory Dynamically 

Memory Management Techniques in Operating System

Importance of Java Memory Management

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