C/Macro Preprocessor/Preprocessor IF

IF and endif preprocessor

<source lang="cpp">

1. include <stdio.h>
2. define TEST 29
3. if defined TEST

int main(void) {

 printf("This is a test.\n");
 return 0;

}

1. endif

      </source>

ifdef preprocessor

<source lang="cpp">

1. include <stdio.h>
2. define DOG

int main(void) {

1. ifdef DOG

 printf("DOG is defined.\n");

1. endif
2. undef DOG
3. ifdef DOG

 printf("This line is not compiled.\n");

1. endif

 return 0;

}

      </source>

#IF #ELSE #ENDIF

<source lang="cpp"> //file1.h

1. define USD 1

//file2.h

1. define UKP 1

//file3

1. include <stdio.h>
2. include <file1.h>
3. if (defined (USD))

   #define currency_rate 46

1. else

   #define currency_rate 100 

1. endif

main() {

 int rs;
 rs = 10 * currency_rate;
 printf ("d\n", rs);

}

      </source>