Program to understand the use of realloc function

/*program to understand the use of realloc function */
#include<stdio.h>
#include<alloc.h>
#include<string.h>
main ( )
{
    char *ptr;
    ptr = ( char * ) malloc ( 6 );
    ptr = "ankit";
    printf ("%s is in memory block\n",ptr );
    ptr = ( char * ) realloc ( ptr,8);
    printf ("%s is in memory block\n",ptr );
    strcpy ( ptr , "rishabh" );
    printf ("Now %s is in memory block\n",ptr );
}