tommy_chai: Just so you know, ChiefDelphi isn't primarily for programming questions, so you might get a faster and/or more complete response in a different forum.
http://www.chiefdelphi.com/forums/sh...ad.php?t=29944
If you're using ANSI C, this is typically done using the extern keyword. The other option is to use "getter" functions, like you would in object-oriented programming.
Note that you'll probably want to put the declaration of Coordinate and your functions into a header file, which you can include in both of your c files.
Hope this helps.