Error: macro names must be identifiers using #ifdef 0

Question

I have the source code of an application written in C++ and I just want to comment something using:

#ifdef 0
...
#endif

And I get this erro

Answer 1

This error can also occur if you are not following the marco rules

Like

#define 1K 1024 // Macro rules must be identifiers error occurs

Reason: Macro Should begin with a letter, not a number

Change to

#define ONE_KILOBYTE 1024 // This resolves