#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>

#include <errno.h>
extern int errno;

#define M 100
#define K 400 * Q
#define SQUARE(X) X * X
#define Q 4
#define U 10 * U
#define SWAP(TYPE,A,B) {TYPE tmp=A; A=B; B=tmp;}
#define MAX(A,B) ( (A) > (B) ? (A) : (B) )

int f( int z )
{
 printf( "In f() -- Money Transferred.\n" );
 /* does some critical stuff */
 return z * 10;
}

int main( int argc, char *argv[] )
{
 int i;
 int x = M;
 int y = SQUARE(K);
 int z = MAX( x, f(y) );
 printf( "maximum is %d\n", z );

 for ( i = 0 ; i < argc ; i++ ) {
   printf( "argument %d is %s\n", i, argv[i] );
 }

 if ( argc != 2 ) {
   fprintf( stderr, "ERROR: Invalid usage\n" );
   fprintf( stderr, "USAGE: %s <filename>\n", argv[0] );
   exit( 1 );
 }

 { /* new scope */
   int rc = open( argv[1], O_RDONLY, 0 );
   if ( rc < 0 ) {
     printf( "errno is %d\n", errno );
     perror( "Error opening file" );
   }
 }

 printf( "Hi.\n" );
 printf( "x is %d and y is %d\n", x, y );
 SWAP( int, x, y )  /* NO ; HERE */
 printf( "x is %d and y is %d\n", x, y );

 return 0;
}