define macro : ifdef « Development « C++ Tutorial

1. C++ Tutorial
2. Development
3. ifdef

#define DemoVersion
 #define PC 5

 #include <iostream>
 
 int main()
 {
     std::cout << "Checking on the definitions of DemoVersion,PC and MAC...\n";

 
 #ifdef DemoVersion
     std::cout << "DemoVersion defined.\n";
 #else // DemoVersion
     std::cout << "DemoVersion not defined.\n";
 #endif // DemoVersion
 
 #ifndef PC
     std::cout << "PC not defined!\n";
 #else // PC
     std::cout << "PC defined as: " << PC << std::endl;
 #endif // PC
 
 #ifdef MAC
     std::cout << "MAC defined!\n";
 #else // MAC
     std::cout << "MAC was not defined.\n";
 #endif // MAC
 
     std::cout << "Done.\n";
     return 0;
 }

Checking on the definitions of DemoVersion,PC and MAC...
DemoVersion defined.
PC defined as: 5
MAC was not defined.
Done.