1. Unless C's variable definition rules are completely different from C++'s, int i; is a full definition, not a declaration. If both definitions appear at the same scope (e.g. global), this will cause either a compiler error or a linker error. A variable declaration would be extern int i;
at file scope is a tentative definition - if, by the end of the compilation unit, no definition has been seen, one of them will become a definition, otherwise it is just a declaration.
