Global variables & multiple stacks

[Barry Levine]

I have two separate stacks that have, up to this point, been compiled 
as separate programs. I now need to combine them into one program so 
I'll probably create a "splash screen" stack as a new project's main 
stack and make the two (previously separate) stacks into sub-stacks of 
the splash screen stack. (Any disagreement?)

What happens if I have identical global variables that I've 
accidentally used in both (previously separate) stacks? Are global 
var's truly global in that the data they hold are shared among all 
sub-stacks? I think I know the answer (yes - which means I'll have to 
change the var's in one of the stacks) but I wanted to ask anyway.

Are there variable types that are only "global" to a stack?

Thanks,
Barry