Program to understand the use of realloc() function

#include<stdio.h>
#include<stdlib.h>
main( )
{
int i, *ptr;
ptr = (int *)malloc(5 *sizeof(int));
if(ptr == NULL)
{
printf("Memory not available\n");
exit(1);
}
printf("Enter 5 integers : ");
for(i=0; i<5; i++)
scanf("%d", ptr+i);
/*Allocate memory for 4 more integers*/
ptr = (int *)realloc(ptr, 9*sizeof(int));
if(ptr == NULL)
{
printf("Memory not available\n");
exit(1);
}
printf("Enter 4 more integers : ");
for(i=5; i<9; i++)
scanf("%d", ptr+i);
for(i=0; i<9; i++)
printf("%d ", *(ptr+i));
}