preprocessors

If else preprocessors

 

-----------------------code------------------------------

#include <iostream.h>

 

#define DAY     0

#define  NIGHT   1

 

#define  NOW   DAY

 

#define ISNIGHT x          ((x)==NIGHT)

 

int main( void )

{

#if         ISNIGHT(1)

            std:cout << "Good Night World" << endl;

#else

            std:cout << "Hello World" << endl;