Hi,
I tried it this way...

Put all my definitions in "DEFS.C" and declarations in "VARS.H"
in the definitions, I included

struct SENSORS
{
unsigned char ucSTATUS;
unsigned char ucALARM;
unsigned char ucACK;
unsigned char ucBLINK;
unsigned char ucGLOW;
short int siDELAY;
short int siACTUALDELAY;
};
struct SENSORS stSENSOR[8];

and included the line

extern struct SENSORS stSENSOR[8];

in the file VARS.H

I then #included VARS.H in the .C files that use some of the structure variables. But when I try to compile the .C files individually,
I get "error C230: unknown struct/union/enum tag" and also "error C204: undefined member" for all the structure members. Whats still going wrong?

PS: I'll refer K&R as soon as I go home. :). The problem is I've never had the need to write multi-file projects.