#include <stdio.h>

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

   a = 2.0;

   b = f( a ); // The C compiler has NOT seen the definition of float f(float x)
               //   1. IMPLICIT input  conversion: float a          --> DOUBLE
               //   2. IMPLICIT output conversion: int (return val) --> float 
 
   printf("b = %f\n", b);
}

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

   printf("Input parameter = %lf\n", x);

   r = x * x;       // Statement

   return ( r );    // Return statement
}