What is meaning of nonportable pointer conversion in c?

Answer: 

When you will assign any value to a pointer variable then compiler will automatically convert  given value in address  of pointer type such automatic type conversion is known as non-portable pointer conversion. Non-portable pointer conversion is not cause of any compilation error but it is bad coding style. Hence compiler will send one warning message. 

 For example:

#include<stdio.h>

void main(){

    int a =10;

    int *p;

    int **q;

    p=a;  //Nonportable pointer conversion

    q=a; //Nonportable pointer conversion

    printf("%d  %d",*p,**q);

}