#include <stdio.h>

double square( double );       // Declare the square( ) function !!!


int main( int argc, char *argv[] )
{
   double a, b;

   a = 4.0;

   b = square( a );  // Make assumption:  int square(int)
}

double square( double x )                  
{
   double r;        // Define a local variable         

   r = x * x;       // Statement

   return ( r );    // Return statement
}