C语言中的Calloc是什么？

void *calloc ( numbers of elements, size in bytes)

int *ptr;
ptr = (int * ) calloc (500,2);

int *ptr;
ptr = (int * ) calloc (n, sizeof (int));

#include<stdio.h>
#include<stdlib.h>
void main(){
   //Declaring variables, pointers//
   int i,n;
   int *p;
   int even=0,odd=0;
   //Declaring base address p using Calloc//
   p = (int * ) calloc (n, sizeof (int));
   //Reading number of elements//
   printf("Enter the number of elements : ");
   scanf("%d",&n);
   /*Printing O/p -
   We have to use if statement because we have to check if memory
   has been successfully allocated/reserved or not*/
   if (p==NULL){
      printf("Memory not available");
      exit(0);
   }
   //Storing elements into location using for loop//
   printf("The elements are : </p><p>");
   for(i=0;i<n;i++){
      scanf("%d",p+i);
   }
   for(i=0;i<n;i++){
      if(*(p+i)%2==0){
         even=even+*(p+i);
      } else {
         odd=odd+*(p+i);
      }
   }
   printf("The sum of even numbers is : %d</p><p>",even);
   printf("The sum of odd numbers is : %d</p><p>",odd);
}

Enter the number of elements : 4
The elements are :
12
56
23
10
The sum of even numbers is : 78
The sum of odd numbers is : 23