Hi Steve,
C++ has a way to do it (via references), but you want to do it in C.
Hmm.
The usual way of doing it in C is with pointers.
struct lowmem { int foo; /* ... */ };
struct lowmem* gLowmem = (struct lowmem*)0x0400;
int count_foo(void) { return ++gLowmem->foo; }
HTH,
--Eljay