How does malloc and calloc work

The pointer returned is usually of type void. It means that we can assign malloc function to any pointer. The full form of malloc is memory allocation. Calloc function is used to allocate multiple blocks of memory. It is a dynamic memory allocation function which is used to allocate the memory to complex data structures such as arrays and structures.

If this function fails to allocate enough space as specified, it returns null pointer. The full form of calloc function is contiguous allocation. When this statement is successfully executed, a memory space of 50 bytes is reserved. The above syntax is used to allocate n memory blocks of the same size. After the memory space is allocated, all the bytes are initialized to zero.

The pointer, which is currently at the first byte of the allocated memory space, is returned. And, the pointer ptr holds the address of the first byte in the allocated memory. The malloc function allocates memory and leaves the memory uninitialized, whereas the calloc function allocates memory and initializes all bits to zero.

The above statement allocates contiguous space in memory for 25 elements of type float. Dynamically allocated memory created with either calloc or malloc doesn't get freed on their own.

You must explicitly use free to release the space. If the dynamically allocated memory is insufficient or more than required, you can change the size of previously allocated memory using the realloc function. Course Index Explore Programiz. Popular Tutorials Data Types in C. C for Loop. Arrays in C Programming. Pointers in C. Find roots of a quadratic equation. Print Pyramids and Patterns. Check prime number. Print the Fibonacci series. Reference Materials string. Learn to implement data structures like Heap, Stacks, Linked List and many more!

Check out our Data Structures in C course to start learning today. Initialization: malloc allocates memory block of given size in bytes and returns a pointer to the beginning of the block. Return Value: After successful allocation in malloc and calloc , a pointer to the block of memory is returned otherwise NULL value is returned which indicates the failure of allocation.

For instance, If we want to allocate memory for array of 5 integers, see the following program This article is contributed by Shubham Bansal. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute. See your article appearing on the GeeksforGeeks main page and help other Geeks. Skip to content. Change Language.