i.e, malloc(**ptr) -> Memory is allocated only for external pointer of  *(*ptr) which is allocated in form of array. But to provide (*ptr) a memory location , we have to malloc() it again as follows:

malloc(*ptr) ->Now memory is allocated for *ptr .

To  check the amount of memory allocated under **ptr , just print using %d format specifier and as an argument to printf call sizeof(**ptr) .

i.e,

printf(“The size under **ptr is :%d \n”,sizeof(**ptr));