Difference between malloc and calloc?

Question

What is the difference between doing:

ptr = (char **) malloc (MAXELEMS * sizeof(char *));

or:

ptr = (char **) calloc (MAXEL         


        

Answer 1

malloc() and calloc() are functions from the C standard library that allow dynamic memory allocation, meaning that they both allow memory allocation during runtime.

Their prototypes are as follows:

void *malloc( size_t n);
void *calloc( size_t n, size_t t)

There are mainly two differences between the two:

• Behavior: malloc() allocates a memory block, without initializing it, and reading the contents from this block will result in garbage values. calloc(), on the other hand, allocates a memory block and initializes it to zeros, and obviously reading the content of this block will result in zeros.

• Syntax: malloc() takes 1 argument (the size to be allocated), and calloc() takes two arguments (number of blocks to be allocated and size of each block).

The return value from both is a pointer to the allocated block of memory, if successful. Otherwise, NULL will be returned indicating the memory allocation failure.

Example:

int *arr;

// allocate memory for 10 integers with garbage values
arr = (int *)malloc(10 * sizeof(int)); 

// allocate memory for 10 integers and sets all of them to 0
arr = (int *)calloc(10, sizeof(int));

The same functionality as calloc() can be achieved using malloc() and memset():

// allocate memory for 10 integers with garbage values   
arr= (int *)malloc(10 * sizeof(int));
// set all of them to 0
memset(arr, 0, 10 * sizeof(int)); 

Note that malloc() is preferably used over calloc() since it's faster. If zero-initializing the values is wanted, use calloc() instead.