How does the below program output `C89` when compiled in C89 mode and `C99` when compiled in C99 mode?

Question

I\'ve found this C program from the web:

#include 

int main(){

    printf(\"C%d\\n\",(int)(90-(-4.5//**/
    -4.5)));

    return 0;
}
         


        

Answer 1

the line comment // is introduced since C99. Therefore your code is equal to this in C89

#include 

int main(){

    printf("C%d\n",(int)(90-(-4.5/
-4.5)));

    return 0;
}
/* 90 - (-4.5 / -4.5) = 89 */

and equal to this in C99

#include 

int main(){

    printf("C%d\n",(int)(90-(-4.5
-4.5)));

    return 0;
}
/* 90 - (-4.5 - 4.5) = 99*/