Определение констант. #define, #ifdef-#endef

#include <stdio.h>
#define LINE "_____________________"
#define TITLE "Учи язык C и все будет заебись"
#define AUTOR "BlackCoffee"

#ifdef _WIN32
#define SYSTEM "Windows"
#endif

#ifdef linux
#define SYSTEM "Linux"
#endif

int main()
{
    printf("\n \t %s \n \t %s \n", LINE, TITLE);
    printf("\t by %s \n \t %s \n", AUTOR, LINE);
    printf("\n Operation SYSTEM: %s \n", SYSTEM);
    return 0;
}