What the preprocesor '#if 0' and '#if 1' mean?

Question

Ex.
#if 0
// some code...
// ...
#endif

#if 1
// some code...
// ...
#endif

Answer 1

The #if .... #endif part of code is being COMPILED if the #if is true.
In your example #if 0 is the same as #if false, becouse when we convert int to bool every value but 0 is true.This means that somecode1 won't be a part of your code. The same for #if 1 -> #if true,
this time #if returns true so it will be included in your program.

Sory for my english, I'm not a native speaker.