A global variable will work in any file no matter where it is.
#defines are a bit different though. They work in the file that they're defined in as well as any file included after that constant is defined.
So if you had some file that looked like this:
#include 'something.vc'
#define APPLES 10
#define ORANGES 20
#define PEARS 30
int number_of_apples = APPLES; //obviously works
#include 'something_else.vc'
If 'something.vc' contained this code:
...
int number_of_oranges = ORANGES; //ERROR!!
...
You would get a compilation error because ORANGES would be an undefined constant, since 'something.vc' was included before the constant ORANGE was defined.
If 'something_else.vc' contained this code:
...
int number_of_pears = PEARS; //perfectly valid
...
number_of_pears would be able to be set to PEARS as expected and everything would compile fine because 'something_else.vc' was included after the definition of PEARS.
Hope that helped.
BTW, that multi-line thing with the pre tag happens because you're either using Mozilla or Netscape.