#include <stdio.h>

int main()
{
    double  x   = 1.23;
    double  y   = 2.13;
    double  *p  = &x;
    double  **q = &p;

    printf("x = %10.4lf\ny = %10.4lf\n\n", x, y);

    *p = 6.66;

    printf("x = %10.4lf\ny = %10.4lf\n\n", x, y);

    **q = 4.2;

    printf("x = %10.4lf\ny = %10.4lf\n\n", x, y);

    *q = &y;
    *p = 6.66;

    printf("x = %10.4lf\ny = %10.4lf\n\n", x, y);

    **q = 4.2;
    printf("x = %10.4lf\ny = %10.4lf\n\n", x, y);
}