C Reference function calloc()

The function calloc() will allocate a block of memory for an array. All of these elements are size bytes long. During the initialization all bits are set to zero.

Usage of calloc():

void * calloc ( size_t num, size_t size );


Number of elements (array) to allocate and the size of elements.

Return value:

Will return a pointer to the memory block. If the request fails, a NULL pointer is returned.

Source code example of calloc():


	int main ()
		int a,n;
		int * ptr_data;

		printf ("Enter amount: ");
		scanf ("%d",&a);

		ptr_data = (int*) calloc ( a,sizeof(int) );
		if (ptr_data==NULL)
			printf ("Error allocating requested memory");
			exit (1);

		for ( n=0; n<a; n++ )
			printf ("Enter number #%d: ",n);
			scanf ("%d",&ptr_data[n]);

		printf ("Output: ");
		for ( n=0; n<a; n++ )
			printf ("%d ",ptr_data[n]);

		free (ptr_data);
		return 0;

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There are currently 8 responses to “C Reference function calloc()”

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  1. anchre on May 23rd, 2011:

    :)……thx was really helpfull…

  2. Sanjib Das on June 16th, 2011:

    Nice Statement.

  3. Puneet Rana on August 11th, 2011:

    really nyc description ,very brief nd helpful too thx alot .

  4. A.Vivek on March 7th, 2012:


    I have question. What is the difference between calloc(2, sizeof(char)) and calloc(1, sizeof(short))

  5. puja kumari on April 3rd, 2012:

    way of explaining is quite appreciable.i like it.

  6. jamshed on May 4th, 2012:


  7. will on June 7th, 2013:


    In practice, not that much, but whats going on are two things: first is a portability issue; char is pretty universally one byte and short is 2, but who knows, maybe somewhere they’re a different size (this is more of an issue with floats/longs and even ints some places). The second is what you’re storing there and how you want to access it; with C, there’s a workaround for everything – rules are meant to be broken – but if you want two 1-byte elements, do it the first way, if you want 1 2-byte element, do it the second.

  8. Abhishek on July 8th, 2013:

    thanx. It was vry helpfull