don't understand error

When I enter this line in my sketch "#ifdef GENERATE_FORECAST" I get an error "unterminated #ifdef".

I am not sure what to do to clear this message. Thanks!

You need a corresponding #endif at the end of the block. Think of it like opening and closing curly braces

Depends, post your code between code tags, like this:

[code]
Your
  code
    here.
[/code]

Thanks