C89/C99, 25 bytes, 2 versions, score = 12.5

#include <stdio.h> int main() { int v = 11 //**/ 11 + 88; printf("C%d\n", v); return 0; } 

// style comments aren't recognized in C89.

Golfed version:

v(){return 20//**/2 +79;} 

C89/C99, 25 bytes, 2 versions, score = 12.5

#include <stdio.h> int main() { int v = 11 //**/ 11 + 88; printf("C%d\n", v); return 0; } 

// style comments aren't recognized in C89.

Golfed version:

v(){return 20//**/2 +79;} 

Try it online: C89, C99

C89/C99, 29 bytes, 2 versions, score = 14.5

#include <stdio.h> int main() { int v = 11 //**/ 11 + 88; printf("C%d\n", v); return 0; } 

// style comments aren't recognized in C89.

Golfed version:

int v(){return 20//**/2 +79;} 

C89/C99, 25 bytes, 2 versions, score = 12.5

#include <stdio.h> int main() { int v = 11 //**/ 11 + 88; printf("C%d\n", v); return 0; } 

// style comments aren't recognized in C89.

Golfed version:

v(){return 20//**/2 +79;} 

C89/C99

#include <stdio.h> int main() { int v = 11 //**/ 11 + 88; printf("C%d\n", v); return 0; } 

// style comments aren't recognized in C89.

C89/C99, 29 bytes, 2 versions, score = 14.5

#include <stdio.h> int main() { int v = 11 //**/ 11 + 88; printf("C%d\n", v); return 0; } 

// style comments aren't recognized in C89.

Golfed version:

int v(){return 20//**/2 +79;}