ifndef : ifndef « Preprocessor « C Tutorial

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C Tutorial » Preprocessor » ifndef

12.8.1.ifndef

#ifndef is used to check whether a particular symbol is defined.

#define USA 1

//#define EUP 1



#include <stdio.h>



#ifndef USA            

   #define currency_rate 100    

#endif               



#ifndef EUP                 

   #define currency_rate 46

#endif               

main()

{

    int rs;

    rs = 10 * currency_rate; 

    printf ("%d\n", rs);

}

12.8.ifndef
	12.8.1.	ifndef

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