/* --------------------------------------------------------------------- 
**  Figure 12.6:  Call by address. 
** --------------------------------------------------------------------- 
*/
#include <stdio.h>

void f1( int * xp );
void f2( int * xp );

void main( void )
{
    int k = 1;      /* An int variable, initialized to 1. */ 
    printf( "Original value of k: %i\n", k );
    f1( &k );       /* This function changes the value of k. */
    printf( "Changed value of k: %i\n", k );
    f2( &k );       /* This function changes the value of k. */
    printf( "Input is stored in k: %i\n", k );
}

/* --------------------------------------------------------------------- */
void f1( int * xp )   /* xp is an in/out parameter*/
{
    *xp = *xp + 2;   /* add 2 to the old value of xp's referent. */
}

/* --------------------------------------------------------------------- */
void f2( int * xp )   /* xp is an output parameter. */
{
    printf( "Enter an integer: " );
    scanf( "%i", xp );
}