Help needed with #include problems

[john at ntvax.UUCP]

I am using Turboc 1.5 and am having problems linking files. I am writing
a large application (over 64k) and am having trouble breaking up the file.
The question is this, when I #include stdio, stdlib etc in multiple source
modules the compiler and linker have no problems, however, this is not the 
case when i #include my own header files. The compile goes ok but the linker 
gives me the following error - "variable name here" is duplicated in module
"source module name here" . This only occurs for my specfic header files not
the system (stdio, etc). What can I do to get around this problem. Using 
extern may help but the header file is very large. 

Thanks 
john   
convex!ntvax!john