I'm new to c++ programming and I have a problem. Please help.

I'm using the Borland C++ 3.0 compiler. When I try to load programs written
in C code I get linker error messages saying for example: Undefined symbol
_vga256 in module (module).

In this example the _vga256 is a command written as vga256 in the code(
without the _) and its defined using extern in the header file. I've checked
that my header file is in the right directory yet it the compiler doesn't
seem to be including it. At least thats what I figured. I would really
appreciate some assistance here.

Jason